全无机高效钙钛矿发光器件的电注入平衡设计及发光特性研究

Solid-state light-emitting devices (LEDs) based on organometal halide perovskite (OMHP) materials have attracted extensive attention at present. How to design a LED layout to enhance the long-term stability and balance the charge injection, however, is still the unsolved obstacles and needs more investigations. In this application, to solve the problems mentioned above, inorganic p-NiO is planned to be fabricated as a efficient hole-conducting and electron-blocking layer instead of the frequently used organic poly(3,4-ethylenedioxythiophene): poly(styrene sulfonic acid) (PEDOT:PSS) which is known to be harmful to the indium tin oxide (ITO) electrode, while n-ZnO that can be grown easily with various methods in a low price is introduced as the electron-injection and hole-blocking layer. Both of these stable and reliable metal oxides are used to fabricate the high-efficiency and all-inorganic three-dimensional (3D) OMHP (CH3NH3PbI3-xBrx) LEDs. The OMHP LEDs with this layout greatly benefit from the low energy level of the p-NiO conduction band minimum and the relatively high energy level of the n-ZnO valence band maximum, which can confine the electrons and holes in the perovskite active layer effectively in principle, thus enhancing the electroluminescent efficiency of the OMHP LEDs. Impacts of the perovskite crystalline quality, defect types, and surface states on the performance of the OMHP LEDs will be investigated in order to further improve the electroluminescent performance. With perfecting the growth parameters of the inorganic metal oxides (p-NiO and n-ZnO), balancing of the charge injection should be improved and exciton quenching at the interface adjacent to the perovskite active layer should be prevented. Further investigation on the emission properties and related mechanisms will also be conducted with changing the doping factor x, and OMHP LEDs with tunable light emission from the CH3NH3PbI3-xBrx perovskite active layer should be realized. Proposals to further improve the performance of the OMHP LEDs will be given. All the efforts in this application aim to push the investigation and commercialization of the OMHP LEDs forward.

基于有机金属卤化物钙钛矿材料发光器件的研制是目前研究热点之一，如何设计器件结构来提升器件的稳定性、实现电子和空穴的电注入平衡，仍是目前亟待解决的重要问题。申请人拟采用p-NiO取代PEDOT:PSS作为空穴传输层和电子阻挡层，用低成本、易制备的n-ZnO作为电子注入层和空穴阻挡层，制备高效CH3NH3PbI3-xBrx 3D钙钛矿材料全无机发光器件。利用了p-NiO稳定可靠且导带能级较低、而n-ZnO价带能级较高的特点，将空穴和电子有效限制在钙钛矿材料的发光层中，提高器件的发光效率。研究钙钛矿材料的晶体质量、缺陷类型和表面态对器件光电性能的影响。通过逐步优化和改善p-NiO和n-ZnO的制备工艺和参数，进一步提高电子和空穴的电注入平衡，降低激子淬灭几率。研究不同掺杂因子x的钙钛矿有源层材料对发光波长的影响及相应发光机制，实现器件多色发光，为进一步推进钙钛矿材料的发光应用提供指导。

凭借优异的光物理特性，有机无机卤化物钙钛矿材料有望成为最具潜力的下一代平板显示材料之一。然而由于钙钛矿发光器件（PeLED）电荷注入不平衡而导致的发光效率降低问题亟待解决。本项目创新性地引入有机绝缘聚合物聚甲基丙烯酸甲酯（PMMA）来钝化和消除钙钛矿有源层的针孔，降低因漏电而导致的非辐射复合损耗，同时平衡电子和空穴注入，提高载流子在钙钛矿有源层的辐射复合效率，使得在相同偏压下PeLED的发光亮度提高了10倍以上。此外，在ITO与PEDOT:PSS之间引入无机p-NiO作为空穴传输层，不仅极大提高了空穴注入效率，也显著降低了电子溢出，使得在相同偏压下PeLED的发光亮度提高了近一倍。最后，通过调节卤素原子比，制备了发光颜色可调的CH3NH3PbBr3-xClx、CH3NH3PbBr3-xIx钙钛矿材料，并实现了多色电致发光。此研究为进一步开发高稳定、高效率的多色PeLED提供了一些有用的参考。