Quantum dots Materials: Synthesis, Characterization, and Application in Light-Emitting Diodes

• Main Authors: Hung-Chia Wang, 王宏嘉
• Other Authors: Ru-Shi Liu
• Format: Others
• Language: en_US
• Published: 2018
• Online Access: http://ndltd.ncl.edu.tw/handle/6wfwq6

博士 === 國立臺灣大學 === 化學研究所 === 106 === Quantum dots (QDs) attracted significant interests in recent years because of their unique optical properties, such as tunable wavelength, narrow emission, high photoluminescence quantum efficiency (PLQY) and facile solution synthesis. Our quantum dot research could be divided into three major part, (1) perovskite quantum dots (PQDs) used in white-light LEDs, (2) Perovskite quantum dots used in quantum dots light-emitting diodes (QLEDs), (3) Cd-free Indium phosphide quantum dots application in QLEDs. The stability of PQDs requires further improvement to prevent their degradation by temperature, oxygen, moisture, and light. In this thesis, we used mesoporous silica integrated with perovskite quantum dots. This MP-CsPbBr3 nanocomposite show the highly thermal and water resistant. All-inorganic PQDs in white-light LEDs for backlight application. The color gamut overlap of the NTSC space was approximately 113% which is higher than previously phosphor and Cd QDs based white-light LEDs. Furthermore, we demonstrate a hot-injection synthesis of CsPb1-xSnxBr3 perovskite QDs with Sn(IV) substitution. Moreover, Sn(IV) doping can effectively suppress the formation of trions, as revealed by the measurement of single-dot, time-resolved PL, and TA spectroscopies. The best perovskite QLED device displays a luminescence of 12,500 cd/m2, a CE of 11.63 cd/A, an EQE of 4.13%, a power efficiency 6.76 lm/w, and a low turn-on voltage of 3.6 V, which are the highest values among reported Sn-based perovskite QLEDs. Finally, the thick-shelled green InP/ZnSeS/ZnS cadmium-free QDs were used in the inverted QLED device. Cadmium-free thick-shelled InP/ZnSeS/ZnS heter-ostructured quantum dots (QDs) were synthesized using the heating-up approach. In this approach, the InP/ZnSeS/ZnS QDs (7.9 nm) are thicker than the InP/ZnSeS QDs. The inter ZnSeS buffer layer can decrease the lattice mismatch between the InP core and the ZnS outer passivated layer. With the increase in ZnS shell, the stability of the InP QDs can be improved when the QD solution is changed to film type during fabrication. In QLEDs, a thin-shelled InP QD film face numerous problems, such as non-radiative decay, oxygen effect, and Auger recombination. Thick-shelled InP/ZnSeS/ZnS can reduce the effect of these factors, and thus, enhance the efficiency of a QLED device. This inverted thick-shelled InP/ZnSeS/ZnS QLED device exhibits luminescence of over 10000 cd/m2, current efficiency of 4.4 cd/A, power efficiency of 4.32 lm/w, and low turn-on voltage (2.2 V). Results show the good performance of cadmium-free QLEDs.