Uniformity improvement of a mini-LED backlight by a quantum-dot color conversion film with nonuniform thickness.

Mini-LED backlights energized by quantum-dot color conversion (QDCC) hold great potential for technological breakthroughs of liquid crystal displays. However, luminance uniformity issues should still be urgently solved owing to the large interval of direct-lit mini-LEDs, especially when covering with a QDCC film (QDCCF) with uniform thickness. Herein, we propose a uniformity improvement approach of mini-LED backlights by employing a QDCCF with nonuniform thickness based on the Lambertian distribution of mini-LEDs, which is demonstrated by screen-printing preparation and ray-tracing simulation. Experimental results show that the luminance uniformity of the nonuniform QDCCF can reach 89.91%, which is 24.92% higher than the uniform one. Ray-tracing simulation further elaborates the mechanism of this significant improvement. Finally, by employing this nonuniform QDCCF, a mini-LED backlight prototype is assembled and achieves high uniformity of 92.15%, good white balance with color coordinates of (0.3482, 0.3137), and high color gamut of 109% NTSC. This work should shed some new light on mini-LED-based display technology.

Quantum-dot array with a random rough interface encapsulated by atomic layer deposition.

This Letter proposes the use of atomic layer deposition (ALD) encapsulation as a stability-improving approach for a quantum-dot micro-structural array (QDMA) with a random rough interface. The QDMA is first prepared by screen printing technology on an edge-lit light-guide plate (LGP) for backlight application. A flexible aluminum oxide film is then densely deposited onto the rough surface of the QDMA. The influences of two key factors, the reaction temperature and deposition thickness, on the encapsulation effect and output performance of this QD backlight are discussed. After ALD encapsulation, the water vapor transmission rate was measured to be less than 0.014 g/(m2 day). The average luminance of the encapsulated QD backlight remained stable after continuous working for 200 h, while an unencapsulated QD backlight lost over 50% of its initial luminance. The complete attenuation trend for the encapsulated QD backlight was analyzed in a more demanding testing environment, and results showed that 80% (>3000 cd/m2) of the initial luminance was maintained after 250 h at a high temperature of 70 °C and a relative humidity of 90%. The mechanism behind these experimental results is also discussed.

Perovskite Quantum Dots for Emerging Displays: Recent Progress and Perspectives.

The excellent luminescence properties of perovskite quantum dots (PQDs), including wide excitation wavelength range, adjustable emission wavelength, narrow full width at half maximum (FWHM), and high photoluminescence quantum yield (PLQY), highly match the application requirements in emerging displays. Starting from the fundamental structure and the related optical properties, this paper first introduces the existing synthesis approaches of PQDs that have been and will potentially be used for display devices, and then summarizes the stability improving approaches with high retention of PQDs' optical performance. Based on the above, the recent research progress of PQDs in displays is further elaborated. For photoluminescent display applications, the PQDs can be embedded in the backlighting device or color filter for liquid crystal displays (LCD), or they may function as the color conversion layer for blue organic light-emitting diodes (OLED) and blue micro-scale light-emitting diodes (µLED). In terms of next-generation electroluminescent displays, notable progress in perovskite quantum-dot light emitting diodes (PeQLED) has been achieved within the past decade, especially the maximum external quantum efficiency (EQE). To conclude, the key directions for future PQD development are summarized for promising prospects and widespread applications in display fields.