Direct patterning and optical properties of quantum dot films based on UV micro-LEDs

Quantum dots (QDs) are a promising material for color conversion, and their combination with micro light-emitting diode(micro-LED) devices holds great promise for applications in areas such as displays and optical communications. In this study, QD films with different colors and layers were prepared, and different QD patterns with pixel sizes of 14-20 µm were directly patterned on the QD films using a maskless photolithography system based on micro-LEDs. Furthermore, the optical properties of QD films under 405 nm micro-LED excitation were investigated. The results show that the 3-layer QD films of all colors exhibited the highest photoluminescence (PL) intensities. The 3-layer QD films also achieved the highest average absorption ratios (red: ∼ 99.4%, green: ∼ 99.2%, blue: ∼ 82.2%, orange: ∼93.9%) and power conversion efficiency (PCE) values (red: ∼ 31.4%, green: ∼ 35.8%, blue: ∼ 13.8%, orange: ∼ 23.7%). However, compared with the 1-layer QD films, the PCE values, average conversion ratios, and photoluminescence quantum yields (PLQYs) of the 3-layer QD films did not increase significantly, while some values slightly decreased due to the light leakage caused by substrate reflections. Therefore, different distributed Bragg reflector (DBR) solutions were used to reduce light leakage and improve the optical conversion performance of the 3-layer QD films. The experimental results show that the PCE values, average conversion ratios, and PLQYs of 3-layer QD films were improved by applying DBR solutions. The best improvement results are as follows: PCE values increased by 6.8% (red), 7.3% (green), 3.0% (blue), and 2.6% (orange); average conversion ratios increased by 7.0% (red), 7.4% (green), 4.2% (blue), and 2.8% (orange); and PLQYs increased by 10.9% (red), 9.9% (green), 4.8% (blue), and 4.2% (orange).