QLED vs OLED | Difference between QLED TV and OLED TV

This page compares QLED vs OLED and mentions difference between QLED TV and OLED TV. It mentions comparison between LED and LCD display types including OLED basics,OLED advantages and disadvantages, OLED working.

OLED | Organic Light Emitting Diode

OLED Structure, How OLED Works

• It is electronic device made by placing series of organic thin films between the two conductors.
• It works based on principle of electro-luminescence which states a bright light is emitted when electrical current is being applied.
• OLED structure consists of Cathode, Emissive Layer, Conductive Layer, Anode and substrate.
• When voltage is applied to OLED, current flows from cathode to the anode through the organic layers.
• Due to above electrons are travelled towards emissive layer and removed from conductive layer.
• Removal of electrons from conductive layer leave out holes which need to be filled with electrons in emissive layer.
• As a result, holes jump to emissive layer and will re-combine with electrons. As electrons drop into holes, they release their extra energy as light. This way, light emission takes place in the OLED device.

QLED | Quantum-dot Light Emitting Diode

Quantum dots are key elements for QLED and IGZO display technologies. Let us understand quantum dots.

What are Quantum dots ?
• They are tiny semiconductor neon scale crystals having size between 2 nm to 10 nm.
• Quantum dots emit colors based on their size and energy gap of materials used. The bigger the dimension, larger is the emitted wavelength.
• The figure-2 depicts graph of wavelength versus fluorescence.

Quantum dot Color Emission Spectrum

• Many different semiconductor materials are used to make quantum dots viz. CdSe, CdS, PbSe, PbS, InAs, InP etc.
• Now-a-days Cadmium-free technologies are used as these technologies generate numerous color combinations which provide better light efficiency.

QLED image construction

• In QLED construction, thin layer of quantum dots is used in front of backlight.
• As shown in the figure-3, 6 layers are used to construct the color image viz. backlight panel, reflector, polarising filter, TFT array, colour filter glass, quantum dots colour filter and polarising filter.
• Backlight panel: It illuminates LED from side or back of display panel. It uses special source of light to produce visible image. This light is passed to the reflector.
• Reflector: It enhances uniformity of the illuminance distribution on target region of the image plane.
• Polarising filter: It is used to change the settings of the image passed by the reflector in order to suppress glare or blur in image. There are various polarisers used in display technology.
• TFT array: It matches size with quantum dots in the color filter and carries out colour re-production. It handles display of pixels on the screen.
• Colour filters with blue LED can produce billions of colours with peak brightness and better clarity.
• Polarising filter: It gives final touch to display in order to generate crystal clear image of the screen.
• Refer advantages and disadvantages of quantum dots used in the construction of QLED.

Tabular difference between QLED vs OLED TV types

• OLEDs illuminate the LEDs themselves. Hence OLED do not need any light source.
• QLEDs do not produce light by themselves. Instead QLEDs use backlight unit for illumination. This light is passed to the reflector as shown in order to have uniform illumination on the image plane. Quantum dots resist moisture better and hence QLED TV will have longer life. Moreover due to high resistance to moisture, it does not need expensive vacuum evaporation process.
• Following table mentions basic difference between QLED vs OLED TV types.

Specifications OLED TV (nanophotonica) QLED TV
Principle Emissive Transmissive
Backlight It emits light itself and hence does not require any backlight. Uses LED backlight
Cost High Low
Power Consumption Medium Low
Display size From 55 inches up to 88-inch OLED TVs are available 100 inches and beyond
Life Span Less More
Viewing angle Narrow or Wide (OLED with color filters has wide angle, but direct emission RGB OLED uses outcoupling structure which keeps emission purity to very narrow viewing angles). Wide (QLED emits with equal brightness in all the directions).
Switching Speed Medium Fast
Weight Thin and Light in weight Thin and Light in weight
Flexibility Flexible & portable structure Flexible & portable structure

This guide provides comparison between QLED vs OLED and their respective TV types.

Comparison between OLED, LED and LCD

Refer OLED vs LED vs LCD>> and LED vs LCD>> which mentions basic comparison between OLED, LED and LCD with respect to their features.

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