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By Samsung Newsroom
Health and fitness are the most popular features for Galaxy Watches running Wear OS powered by Samsung. Implementing these features requires a continuous data stream to work effectively and seamlessly.
One of the most common challenges third-party developers face is keeping a sensor like the heart rate monitor active, even when the watch screen is off.
By default, Wear OS efficiently optimizes power consumption to extend usage time. As part of this optimization, sensor data collection may stop when the screen is off. This presents a challenge for applications that require continuous monitoring, such as health trackers, workout assistants, or medical-grade wearables.
What Happens When the Screen Turns Off
When a Galaxy Watch screen turns off, the system enters a low-power state to preserve battery. During this time:
The CPU may slow down or suspend execution of background threads. Registered sensor listeners can stop receiving updates. Any active work in your Activity pauses. To keep sensor data flowing, your application needs two things:
A foreground service to keep your code running in the background. A wake lock to prevent the CPU from going into a deep sleep state. This tutorial shows how to create a simple Galaxy Watch application that continuously collects heart rate data, even when the screen is off, using a foreground service and a wake lock and all the code examples are provided in a downloadable sample application.
Let's Start Coding
Step 1: Create a New Wear OS Project
Open Android Studio and create new project from scratch:
Go to File > New > New Project > Wear OS Tab > Empty Wear App. Fill in the project details in the New Project window.
Figure 1: Create a new wearable application in Android Studio
Click Finish and wait for Gradle sync to complete. Step 2: Configure Permissions in AndroidManifest.xml
In the AndroidManifest.xml file, add the following permissions to access the heart rate sensor, foreground service, and wake lock.
<uses-permission android:name="android.permission.BODY_SENSORS" /> <uses-permission android:name="android.permission.FOREGROUND_SERVICE" /> <uses-permission android:name="android.permission.FOREGROUND_SERVICE_HEALTH" /> <uses-permission android:name="android.permission.WAKE_LOCK" /> <uses-permission android:name=" android.permission.BODY_SENSORS_BACKGROUND " /> <uses-feature android:name="android.hardware.type.watch" /> NoteThe BODY_SENSORS_BACKGROUND permission is required on Android 12 (API 31) and above for collecting sensor data when the application is not in the foreground. Register the SensorService in the manifest:
<service android:name=".SensorService" android:enabled="true" android:exported="false" android:foregroundServiceType="health" /> NoteIf you forget foregroundServiceType="health" in the manifest, your application will crash with a SecurityException on Android 10 (API 29) and above when trying to read sensors from a foreground service. Step 3: Design Your Watch UI Layout
The watch UI can be designed entirely according to your preference. In this content, only two buttons have been used to start and stop the service and a TextView to show the result to keep it simple. Wear OS screens are small, so keeping the layout simple is the best practice.
To implement the UI, edit app/res/layout/activity_main.xml.
The following code implements a sample UI:
<?xml version="1.0" encoding="utf-8"?> <androidx.constraintlayout.widget.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res/android" xmlns:app="http://schemas.android.com/apk/res-auto" xmlns:tools="http://schemas.android.com/tools" android:layout_width="match_parent" android:layout_height="match_parent" android:padding="16dp" tools:context=".MainActivity" tools:deviceIds="wear"> <LinearLayout android:layout_width="match_parent" android:layout_height="match_parent" android:gravity="center" android:orientation="vertical"> <TextView android:id="@+id/heart_rate_text" android:layout_width="wrap_content" android:layout_height="wrap_content" android:text="--" android:textColor="#90EE90" android:textSize="24sp" android:layout_marginBottom="16dp"/> <Button android:id="@+id/start_button" android:layout_width="wrap_content" android:layout_height="wrap_content" android:text="@string/start_sensors" /> <Button android:id="@+id/stop_button" android:layout_width="wrap_content" android:layout_height="wrap_content" android:layout_marginTop="8dp" android:text="@string/stop_sensors" /> </LinearLayout> </androidx.constraintlayout.widget.ConstraintLayout> Step 4: Edit MainActivity.java
Inside MainActivity.java, sensor permissions must be requested at runtime.
onCreate() :
You need to initialize all the UI components inside the onCreate() method. This example uses two Button instances, for starting and stopping the service, and one TextView , for showing the result. Before staring the service, you have to check all the runtime permissions.
heartRateTextView = findViewById(R.id.heart_rate_text); //initialize globally to use it outside of the method Button startButton = findViewById(R.id.start_button); Button stopButton = findViewById(R.id.stop_button); if (startButton != null) { startButton.setOnClickListener(v -> { if (checkPermissions()) { if (checkBackgroundPermission()) { startSensorService(); } else { requestBackgroundPermission(); } } else { requestPermissions(); } }); } if (stopButton != null) { stopButton.setOnClickListener(v -> stopSensorService()); } In this application, when the user taps the start button, the application checks both permissions in sequence, and the stop button stops the service.
NoteOn Android 11 (API 30) and above, BODY_SENSORS_BACKGROUND must be requested as a separate step after foreground sensor permission is granted. The system does not grant this permission automatically.
checkPermissions() :
This method checks at runtime whether the BODY_SENSORS permission has been granted. On Galaxy Watch, the user must explicitly grant this permission on their device.
private boolean checkPermissions() { return ContextCompat.checkSelfPermission(this, Manifest.permission.BODY_SENSORS) == PackageManager.PERMISSION_GRANTED; }
checkBackgroundPermission() :
This method checks for the BODY_SENSORS_BACKGROUND permission, which is essential for Wear OS 3+ devices (like Galaxy Watch 5, 6, 7) to access sensor data in all power states.
private boolean checkBackgroundPermission() { if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.Q) { return ContextCompat.checkSelfPermission(this, Manifest.permission.BODY_SENSORS_BACKGROUND) == PackageManager.PERMISSION_GRANTED; } return true; }
startForegroundService() :
On Android 8 (Oreo) and above, you must call this method instead of startService() when starting a foreground service.
private void startSensorService() { Intent intent = new Intent(this, SensorService.class); if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.O) { startForegroundService(intent); } else { startService(intent); } Toast.makeText(this, "Sensor Service Started", Toast.LENGTH_SHORT).show(); }
stopSensorService() :
Once the task is completed, call this method to reduce battery drain.
private void stopSensorService() { Intent intent = new Intent(this, SensorService.class); stopService(intent); if (heartRateTextView != null) { heartRateTextView.setText("--"); } Toast.makeText(this, "Sensor Service Stopped", Toast.LENGTH_SHORT).show();
requestPermissions() :
This method prompts the user for the BODY_SENSORS permission before starting the service.
private void requestPermissions() { ActivityCompat.requestPermissions(this, new String[]{Manifest.permission.BODY_SENSORS}, PERMISSION_REQUEST_CODE); }
requestBackgroundPermission() :
This method prompts the user for the BODY_SENSORS_BACKGROUND permission. Since the sample application targets Android 13 (API level 33) or higher (currently set to 34), this permission is required if you want to access sensor data in the background, even when using a foreground service. Without it, the system can restrict or stop sensor data delivery when the application is not in the immediate foreground for an extended period.
private void requestBackgroundPermission() { if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.Q) { Toast.makeText(this, "Please allow 'All the time' sensor access in settings",Toast.LENGTH_LONG).show(); // On API 30+, background permission MUST be requested separately and // the user must be directed to settings manually in many cases, or through a system dialog. ActivityCompat.requestPermissions(this, new String[]{Manifest.permission.BODY_SENSORS_BACKGROUND}, BACKGROUND_PERMISSION_REQUEST_CODE); } } Override the onRequestPermissionsResult() method to handle the user's response to each permission request:
@Override public void onRequestPermissionsResult(int requestCode, @NonNull String[] permissions, @NonNull int[] grantResults) { super.onRequestPermissionsResult(requestCode, permissions, grantResults); if (requestCode == PERMISSION_REQUEST_CODE) { if (grantResults.length > 0 && grantResults[0] == PackageManager.PERMISSION_GRANTED) { if (checkBackgroundPermission()) { startSensorService(); } else { requestBackgroundPermission(); } } else { Toast.makeText(this, "Permission denied to read sensors", Toast.LENGTH_SHORT).show(); } } else if (requestCode == BACKGROUND_PERMISSION_REQUEST_CODE) { if (grantResults.length > 0 && grantResults[0] == PackageManager.PERMISSION_GRANTED) { startSensorService(); } else { Toast.makeText(this, "Background permission denied. Data collection may stop when app is not in foreground.", Toast.LENGTH_LONG).show(); // Optionally start service anyway, knowing it might be limited startSensorService(); } } } Even if the background permission is denied, the service is started. This allows heart rate collection to continue while the application is visible, though data collection may pause when it moves to the background.
BroadcastReceiver:
Send an intent with the heart rate value to update the UI components in real time. This should be outside of the onCreate() method.
private final BroadcastReceiver heartRateReceiver = new BroadcastReceiver() { @Override public void onReceive(Context context, Intent intent) { if (SensorService.ACTION_HEART_RATE_UPDATE.equals(intent.getAction())) { float heartRate = intent.getFloatExtra(SensorService.EXTRA_HEART_RATE, 0); if (heartRateTextView != null) { heartRateTextView.setText(String.format(Locale.getDefault(), "%.0f", heartRate)); } } } };
onResume() :
Register a BroadcastReceiver inside this method to catch updates and display them in a TextView element.
@Override protected void onResume() { super.onResume(); IntentFilter filter = new IntentFilter(SensorService.ACTION_HEART_RATE_UPDATE); if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.TIRAMISU) { registerReceiver(heartRateReceiver, filter, Context.RECEIVER_NOT_EXPORTED); } else { registerReceiver(heartRateReceiver, filter); } }
onDestroy() :
This method stops the service when the activity is destroyed, preventing a dangling service.
@Override protected void onDestroy() { stopSensorService(); super.onDestroy(); }
Step 5: Edit SensorService.java
This is the core of the tutorial. SensorService is a foreground service that registers a heart rate sensor listener and acquires a wake lock to keep the CPU active when the screen turns off.
onCreate() :
Initialize the SensorManager instance and request the wake-up sensor. Here, do not use the default sensor. Instead, request the wake-up version:
sensorManager = (SensorManager) getSystemService(Context.SENSOR_SERVICE); if (sensorManager != null) { // Attempt to get the wake-up version of the sensor heartRateSensor = sensorManager.getDefaultSensor(Sensor.TYPE_HEART_RATE, true); if (heartRateSensor == null) { Log.i(TAG, "Wake-up heart rate sensor not available, falling back to non-wake-up."); heartRateSensor = sensorManager.getDefaultSensor(Sensor.TYPE_HEART_RATE); } } Standard sensors stop sending data when the screen turns off. The true parameter ensures the sensor can wake up the processor to deliver data even in deep sleep.
onStartCommand() :
Execute the foreground service notification.
Promoting your service to the foreground is mandatory for the tracking to stay alive. This prevents Galaxy Watch from pausing your application after 60 seconds of screen-off time.
Promote Immediately: In onStartCommand(), promote the service to the foreground immediately to satisfy Android’s background limitations.
Build the Notification: Create a persistent notification that informs the user that heart rate tracking is active.
Specify Service Type: Android 10+ requires the FOREGROUND_SERVICE_TYPE_HEALTH type for health sensors.
Register Listener: Register the sensor listener to begin receiving heart rate events.
Check the code here:
@Override public int onStartCommand(Intent intent, int flags, int startId) { Notification notification = new NotificationCompat.Builder(this, CHANNEL_ID) .setContentTitle(getString(R.string.sensor_notification_title)) .setContentText(getString(R.string.sensor_notification_text)) .setSmallIcon(android.R.drawable.ic_menu_info_details) .setPriority(NotificationCompat.PRIORITY_DEFAULT) .build(); if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.Q) { startForeground(1, notification, ServiceInfo.FOREGROUND_SERVICE_TYPE_HEALTH); } else { startForeground(1, notification); } if (heartRateSensor != null) { sensorManager.registerListener(this, heartRateSensor, SensorManager.SENSOR_DELAY_UI); Log.d(TAG, "Heart rate sensor registered."); } else { Log.e(TAG, "Heart rate sensor not available."); } return START_STICKY; }
onSensorChanged() :
To process sensor data and broadcast updates, implement this method to handle the actual data.
Capture Value: Extract the heart rate from event.values[0].
Broadcast Result: Send a local broadcast with the heart rate value so your UI components can update in real-time.
Here is the code:
@Override public void onSensorChanged(SensorEvent event) { if (event.sensor.getType() == Sensor.TYPE_HEART_RATE) { float heartRate = event.values[0]; Log.d(TAG, "_________Heart Rate: " + heartRate); // Broadcast the result to update the UI Intent intent = new Intent(ACTION_HEART_RATE_UPDATE); intent.putExtra(EXTRA_HEART_RATE, heartRate); intent.setPackage(getPackageName()); // Ensure only this app receives the broadcast sendBroadcast(intent); } }
onDestroy() :
In this method, unregister the sensor listener to prevent excessive battery drain after the user is finished.
@Override public void onDestroy() { if (sensorManager != null) { sensorManager.unregisterListener(this); //Stop sensor } Log.d(TAG, "Sensor service destroyed and listener unregistered."); super.onDestroy(); } Step 6: Download the Sample Application
You may download the final projects here:
SensorReadConExample (556.0 KB) 04/23/2026 Step 7: Run the Sample Application on Galaxy Watch
To run the sample application on a Galaxy Watch:
Connect Galaxy Watch to Android Studio over Wi-Fi. Run the sample application on your device. Tap START SENSORS and grant the sensor permission when prompted. When you see the second prompt (or toast), go to the System Settings > Apps > Permissions > Sensors and select All the time. Once granted, the data collection continues even if you close the application UI or the watch screen goes dark.
When the screen turns off, heart rate logs continue in Android Studio Logcat. Tap STOP SENSORS when you want to stop data collection. This stops the service.
Figure 2: Sample application output on a real device
Figure 3: Data collection output in Logcat
In Logcat, filter by the SensorService tag to see the collected heart rate readings. New readings arrive even while the watch screen is off.
NoteYou need to wear the watch to read the heart rate data. Otherwise, it shows 0.0 as the value. Conclusion
Following the steps above, you can build a Galaxy Watch application that collects heart rate data continuously—even when the screen turns off. This same approach applies to other sensors as well, allowing you to read any sensor data continuously in the background.
If you have any questions about or need help with the information in this article, you can reach out to us on the Samsung Developers Forum or contact us through Developer Support.
View the full blog at its source
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By Samsung Newsroom
The Entertainment Companion zone at The First Look 2026 marked a new chapter in Samsung’s visual display evolution — building on two decades as the world’s No. 1 TV brand. The space was divided into art, gaming and entertainment sections, anchored by the world’s first 130-inch Micro RGB TV and the Vision AI Companion.
Samsung Newsroom stepped inside the exhibition to see how hardware innovation and AI-driven visual intelligence come together to create new immersive experiences.
▲ Samsung has been the world’s No. 1 TV brand for the past 20 years.
Micro RGB 130”: CES Innovation Awards 2026 Best of Innovation Winner
The Micro RGB 130” TV made its debut at First Look. Visitors were first struck by its scale, then by the precision of its color reproduction across varied content. Micro RGB 130” also delivers 100% of the BT.2020 wide color gamut, certified by Verband der Elektrotechnik (VDE), to enable more accurate, life-like colors.
As screen sizes grow, maintaining image consistency becomes more challenging. Samsung addressed this with Glare Free technology, enabling uniform image rendering without distracting reflections — a key reason the Micro RGB 130” TV earned a CES Innovation Awards 2026 Best of Innovation honor.
▲ Micro RGB 130” ▲ The Micro RGB 130” TV uses RGB color LEDs smaller than 100 micrometers as its backlight to deliver exceptional picture quality and color. ▲ Video explaining how micro RGB LEDs work Beyond the technology, the Micro RGB 130” TV’s Timeless Frame design reflects a modern evolution of Samsung’s TV legacy — preserving the Timeless Gallery concept first introduced at CES 2013. The lower edge of the frame meets the floor, creating the effect of a window that blends seamlessly into its surroundings.
The Micro RGB TVs will be available in 100-, 85-, 75-, 65- and 55-inch sizes.
▲ Video introducing the Micro RGB 130″
Vision AI Companion: From Convenience to Comfort In Everyday Life
▲ Vision AI Companion demonstration “Which team do you think will win today’s soccer match?”
“Can you tell me the recipe for the food on screen?”
The Vision AI Companion area showcased the range of interactions available through the TV. First introduced in 2025, the Vision AI Companion now understands casual, conversational prompts and delivers intelligent responses — from providing detailed information about a film to recommending music based on mood and even placing food orders.
▲ A recipe recommendation via Vision AI Companion
Art TVs: Bringing Art Gallery Experiences Into the Home
The Frame and The Frame Pro
Building on the art experiences offered through Samsung Art Store, Samsung spotlighted its expanded Art TV lineup with a larger The Frame 98”. The built-in Wireless One Connect design simplifies installation, while the packaging box doubles as a wall-mounting guide.
Displayed alongside it, The Frame Pro 85” evoked the feel of a gallery space — showcasing Neo QLED picture quality with vivid clarity.
▲ The Frame 98” and The Frame Pro 85”
OLED S95H
The newly released OLED S95H TV, a CES Innovation Awards 2026 honoree, features an ultra-slim, bezel-free design that resembles a high-end picture frame mounted on the wall.
▲ OLED S95H Art TVs can display more than 5,000 works currently exhibited in museums and other venues around the world. Samsung plans to expand the service through collaborations with global partners.
▲ Art TVs created an immersive chamber where visitors could become part of the piece.
6K Gaming: Immersion on Another Level
Odyssey 3D Monitor
The glasses-free Odyssey 3D 32″ (G90XH6K) — the world’s first 6K 3D gaming monitor — invited visitors to experience their favorite games in new ways. Around 60 games can be enjoyed in 3D including “The First Berserker: Khazan,” “Stellar Blade,” “Lies of P: Overture” and “Mongil: STAR DIVE.”
▲ Odyssey 3D 32” ▲ Jerry Ruiz “I tried gaming in 3D for the first time, and it felt completely new and immersive,” said Jerry Ruiz, a digital content creator from Kennewick, Washington. “Being able to play 3D games without wearing glasses was especially impressive — I don’t think I’ll be able to go back to regular gaming.”
Personalized Entertainment: Tailored to Individual Lifestyles
Tizen
The new Tizen operating system enables personalized recommendations through expanded content discovery. Viewers can access curated programming based on viewing trends and seasonal themes through a simple, intuitive interface.
▲ Tizen delivers personalized entertainment experiences. Samsung extended entertainment beyond watching and listening by inviting visitors to take the mic with Stingray Karaoke on Samsung TV. With microphone connectivity, tambourine effects and applause sounds, the TV transforms into a karaoke system, while features such as echo, reverb and voice tuning recreate the feel of a professional performance. Visitors could also test their skills with Fender Play TV, available exclusively on Samsung TV. The service offers guitar tutorials led by top instructors, along with virtual band sessions through Jam mode.
Available in 30 countries, Samsung TV Plus brings a wide range of entertainment programming — from sports and music to creator content — across more than 3,500 channels and 66,000 video-on-demand titles.
Big Screen, Glare-Free Immersion
The large-display setup demonstrated Samsung’s Glare Free technology, delivering immersive paired with Micro RGB picture quality and spatial audio. The experience reflected Samsung’s vision of the TV as an Entertainment Companion.
▲ Light reflections are visible on the left display but minimized on the right with Glare Free technology.
Portable Screens: Made for Life on the Move
The Freestyle+
One area of the exhibition resembled a camping trip, featuring the new The Freestyle+ projector. Designed for portability, the device lets users enjoy their favorite content wherever they go.
Lightweight and compact, the projector features a minimalist design that blends into any space. AI OptiScreen automatically adjusts the image for different surfaces — including walls, ceilings and curtains — ensuring optimal viewing from virtually anywhere.
▲ The Freestyle+ ▲ AI OptiScreen delivers clear viewing on virtually any surface. In addition, 3D Auto Keystone delivers an optimized, near-rectangular image even when projected onto uneven surfaces such as three-sided corners or curved curtains.
▲ 3D Auto Keystone creates a near-rectangular image even when projected onto a three-sided corner.
Audio Innovation: Sound for Every Space
Music Studio Series and Q-Symphony
Samsung unveiled a range of audio devices in multiple form factors, each made to deliver high-quality sound. Created in a second collaboration with French designer Erwan Bouroullec — following his earlier work with Samsung on The Serif TV — the Music Studio series of Wi-Fi speakers blends refined design with immersive audio, enhancing interior spaces wherever they are placed. The Music Studio series received a CES Innovation Awards 2026 honor.
▲ Music Studio series
Q Series All-in-One Soundbar
Samsung introduced its most cinematic soundbar to date with the new Q Series All-in-One Soundbar. The system features 13 built-in speakers and Sound Elevation technology — which raises dialogue toward the center of the screen. With Auto Volume and flexible installation options including wall mounting or tabletop placement, the soundbar delivers a clearer, more natural listening experience.
▲ Q Series All-in-One Soundbar installation options
Sound Tower
The Sound Tower rounded out the audio lineup. Equipped with a built-in telescopic handle and wheels, the speaker can be easily moved and positioned as needed. Users can adjust lighting colors and effects with Party Lights+ and sound settings to suit different environments. With IPX4 water resistance, the Sound Tower delivers stadium-level energy for an immersive match-day experience.
▲ Sound Tower
Next-Generation Technology: Innovation Beyond the Screen
Micro LED 140″
▲ Micro LED 140″ Using microscopic chips that independently render color, the Micro LED delivered lifelike visuals with exceptional clarity. Shown on a massive 140-inch screen, the imagery created an immersive, cinema-like experience that felt true to life.
▲ Micro LED technology delivers strikingly realistic visuals.
AI Beauty Mirror
▲ AI Beauty Mirror In the next area, visitors entered a space modeled after a powder room where a circular mirror revealed itself as the AI Beauty Mirror. Powered by on-device AI, the technology signaled Samsung’s technology expansion into the beauty space.
The hybrid design combines a polarized mirror with a half mirror to improve reflectivity and transparency, delivering clearer, more precise visuals.
▲ The AI Beauty Mirror provides personalized suggestions through detailed skin analysis.
Audio-Visual Design Blends Sound With Form
A lineup of visually striking audio devices added a strong visual element to the booth. Reimagining the turntable, the Transparent Micro LED functioned as a music visualizer — resembling an LP floating in midair — while a built-in premium sound system ensured audio quality remained uncompromised.
▲ A floating LP-inspired visual audio device
Spatial Signage
Samsung also introduced Spatial Signage, a new display form factor that combines detailed 2D content with immersive 3D effects. Using spatial optical technology measuring just 52 millimeters thick, the display creates a pronounced sense of depth — as if an additional layer of space exists within the screen. The system integrates with existing Samsung signage, enabling centralized remote management of both content and hardware.
With life-size 3D effects and vivid visuals, Spatial Signage can be used for advertising, events, artist exhibitions and museum displays.
▲ The Transparent Micro LED features high transparency and clarity. ▲ Spatial Signage The Entertainment Companion zone at The First Look 2026 went beyond visual and audio enhancements, illustrating how AI can deliver both convenience and comfort when seamlessly integrated into everyday life. Samsung aims to bring greater comfort and enjoyment to everyday life.
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By Samsung Newsroom
“One of the reasons Samsung focused on quantum dots is their exceptionally narrow peaks of the emission spectrum.”
— Sanghyun Sohn, Samsung Electronics
In 2023, the Nobel Prize in Chemistry was awarded for the discovery and synthesis of quantum dots. The Nobel Committee recognized the groundbreaking achievements of scientists in the field — noting that quantum dots have already made significant contributions to the display and medical industries, with broader applications expected in electronics, quantum communications and solar cells.
Quantum dots — ultra-fine semiconductor particles — emit different colors of light depending on their size, producing exceptionally pure and vivid hues. Samsung Electronics, the world’s leading TV manufacturer, has embraced this cutting-edge material to enhance display performance.
Samsung Newsroom sat down with Taeghwan Hyeon, a distinguished professor in the Department of Chemical and Biological Engineering at Seoul National University (SNU); Doh Chang Lee, a professor in the Department of Chemical and Biomolecular Engineering at the Korea Advanced Institute of Science and Technology (KAIST); and Sanghyun Sohn, Head of Advanced Display Lab, Visual Display (VD) Business at Samsung Electronics, to explore how quantum dots are ushering in a new era of display technology.
Understanding the Band Gap Quantum Dots – The Smaller the Particle, the Larger the Band Gap Engineering Behind Quantum Dot Films Real QLED TVs Use Quantum Dots To Create Color
Understanding the Band Gap
“To understand quantum dots, one must first grasp the concept of the band gap.”
— Taeghwan Hyeon, Seoul National University
The movement of electrons causes electricity. Typically, the outermost electrons — known as valence electrons — are involved in this movement. The energy range where these electrons exist is called the valence band, while a higher, unoccupied energy range that can accept electrons is called the conduction band.
An electron can absorb energy to jump from the valence band to the conduction band. When the excited electron releases that energy, it falls back into the valence band. The energy difference between these two bands — the amount of energy an electron must gain or lose to move between them — is known as the band gap.
▲ A comparison of energy band structures in insulators, semiconductors and conductors
Insulators like rubber and glass have large band gaps, preventing electrons from moving freely between bands. In contrast, conductors like copper and silver have overlapping valence and conduction bands — allowing electrons to move freely for high electrical conductivity.
Semiconductors have a band gap that falls between those of insulators and conductors — limiting conductivity under normal conditions but allowing electrical conduction or light emission when electrons are stimulated by heat, light or electricity.
“To understand quantum dots, one must first grasp the concept of the band gap,” said Hyeon, emphasizing that a material’s energy band structure is crucial in determining its electrical properties.
Quantum Dots – The Smaller the Particle, the Larger the Band Gap
“As quantum dot particles become smaller, the wavelength of emitted light shifts from red to blue.”
— Doh Chang Lee, Korea Advanced Institute of Science and Technology
Quantum dots are nanoscale semiconductor crystals with unique electrical and optical properties. Measured in nanometers (nm) — or one-billionth of a meter — these particles are just a few thousandths the thickness of a human hair. When a semiconductor is reduced to the nanometer scale, its properties change significantly compared to its bulk state.
In bulk states, particles are sufficiently large so the electrons in the semiconductor material can move freely without being constrained by their own wavelength. This allows energy levels — the states that particles occupy when absorbing or releasing energy — to form a continuous spectrum, like a long slide with a gentle slope. In quantum dots, electron movement is restricted because the particle size is smaller than the electron’s wavelength.
▲ Size determines the band gap in quantum dots
Imagine scooping water (energy) from a large pot (bulk state) with a ladle (bandwidth corresponding to an electron’s wavelength). Using the ladle, one can adjust the amount of water in the pot freely from full to empty — this is the equivalent of continuous energy levels. However, when the pot shrinks to the size of a teacup — like a quantum dot — the ladle no longer fits. At that point, the cup can only be either full or empty. This illustrates the concept of quantized energy levels.
“When semiconductor particles are reduced to the nanometer scale, their energy levels become quantized — they can only exist in discontinuous steps,” said Hyeon. “This effect is called ‘quantum confinement.’ And at this scale, the band gap can be controlled by adjusting particle size.”
The number of molecules within the particle decreases as the size of the quantum dot decreases, resulting in weaker interactions of molecular orbitals. This strengthens the quantum confinement effect and increases the band gap.1 Because the band gap corresponds to the energy released through relaxation of an electron from the conduction band to the valence band, the color of the emitted light changes accordingly.
“As particles become smaller, the wavelength of emitted light shifts from red to blue,” said Lee. “In other words, the size of the quantum dot nanocrystal determines its color.”
Engineering Behind Quantum Dot Films
“Quantum dot film is at the core of QLED TVs — a testament to Samsung’s deep technical expertise.”
— Doh Chang Lee, Korea Advanced Institute of Science and Technology
Quantum dots have attracted attention across a variety of fields, including solar cells, photocatalysis, medicine and quantum computing. However, the display industry was the first to successfully commercialize the technology.
“One of the reasons Samsung focused on quantum dots is the exceptionally narrow peaks of their emission spectrum,” said Sohn. “Their narrow bandwidth and strong fluorescence make them ideal for accurately reproducing a wide spectrum of colors.”
▲ Quantum dots create ultra-pure red, green and blue (RGB) colors by controlling light at the nanoscale, producing narrow bandwidth and strong fluorescence.
To leverage quantum dots effectively in display technology, materials and structures must maintain high performance over time, under harsh conditions. Samsung QLED achieves this through the use of a quantum dot film.
“Accurate color reproduction in a display depends on how well the film utilizes the optical properties of quantum dots,” said Lee. “A quantum dot film must meet several key requirements for commercial use, such as efficient light conversion and translucence.”
▲ Sanghyun Sohn
The quantum dot film used in Samsung QLED displays is produced by adding a quantum dot solution to a polymer base heated to a very high-temperature, spreading it into a thin layer and then curing it. While this may sound simple, the actual manufacturing process is highly complex.
“It’s like trying to evenly mix cinnamon powder into sticky honey without making lumps — not an easy task,” said Sohn. “To evenly disperse quantum dots throughout the film, several factors such as materials, design and processing conditions must be carefully considered.”
Despite these challenges, Samsung pushed the boundaries of the technology. To ensure long-term durability in its displays, the company developed proprietary polymer materials specifically optimized for quantum dots.
“We’ve built extensive expertise in quantum dot technology by developing barrier films that block moisture and polymer materials capable of evenly dispersing quantum dots,” he added. “Through this, we not only achieved mass production but also reduced costs.”
Thanks to this advanced process, Samsung’s quantum dot film delivers precise color expression and outstanding luminous efficiency — all backed by industry-leading durability.
“Brightness is typically measured in nits, with one nit equivalent to the brightness of a single candle,” explained Sohn. “While conventional LEDs offer around 500 nits, our quantum dot displays can reach 2,000 nits or more — the equivalent of 2,000 candles — achieving a new level of image quality.”
▲ RGB gamut comparisons between visible light spectrum, sRGB and DCI-P3 in a CIE 1931 color space
* CIE 1930: A widely used color system announced in 1931 by the Commission internationale de l’éclairage
* sRGB (standard RGB): A color space created cooperatively by Microsoft and HP in 1996 for monitors and printers
* DCI-P3 (Digital Cinema Initiatives – Protocol 3): A color space widely used for digital HDR content, defined by Digital Cinema Initiatives for digital projectors
By leveraging quantum dots, Samsung has significantly enhanced both brightness and color expression — delivering a visual experience unlike anything seen before. In fact, Samsung QLED TVs achieve a color reproduction rate exceeding 90% of the DCI-P3 (Digital Cinema Initiatives – Protocol 3) color space, the benchmark for color accuracy in digital cinema.
“Even if you have made quantum dots, you need to ensure long-term stability for them to be useful,” said Lee. “Samsung’s industry-leading indium phosphide (InP)-based quantum dot synthesis and film production technologies are testament to Samsung’s deep technical expertise.”
Real QLED TVs Use Quantum Dots To Create Color
“The legitimacy of a quantum dot TV lies in whether or not it leverages the quantum confinement effect.”
— Taeghwan Hyeon, Seoul National University
As interest in quantum dots grows across the industry, a variety of products have entered the market. Nonetheless, not all quantum dot-labeled TVs are equal — quantum dots must sufficiently contribute to actual image quality.
▲ Taeghwan Hyeon
“The legitimacy of a quantum dot TV lies in whether or not it leverages the quantum confinement effect,” said Hyeon. “The first, fundamental requirement is to use quantum dots to create color.”
“To be considered a true quantum dot TV, quantum dots must serve as either the core light-converting or primary light-emitting material,” said Lee. “For light-converting quantum dots, the display must contain an adequate amount of quantum dots to absorb and convert blue light emitted by the backlight unit.”
▲ Doh Chang Lee
“Quantum dot film must contain a sufficient amount of quantum dots to perform effectively,” repeated Sohn, emphasizing the importance of quantum dot content. “Samsung QLED uses more than 3,000 parts per million (ppm) of quantum dot materials. 100% of the red and green colors are made through quantum dots.”
Samsung began developing quantum dot technology in 2001 and, in 2015, introduced the world’s first no-cadmium quantum dot TV — the SUHD TV. In 2017, the company launched its premium QLED lineup, further solidifying its leadership in the quantum dot display industry.
In the second part of this interview series, Samsung Newsroom takes a closer look at how Samsung not only commercialized quantum dot display technology but also developed a cadmium-free quantum dot material — an innovation recognized by Nobel Prize-winning researchers in chemistry.
1 When a semiconductor material is in its bulk state, the band gap remains fixed at a value characteristic of the material and does not depend on particle size.
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