溶液法制备溴氯混合钙钛矿薄膜及其在蓝光LED中的应用研究

Organic-inorganic hybrid perovskite has become a hot research topic in material science and optoelectronic devices due to its unique optoelectronic properties. Perovskite light emitting diodes (PeLEDs) are very promising due to its favorable optoelectronic properties such as tunable bandgap, high photoluminescence quantum yield etc. However, the external quantum efficiency (EQE) of blue PeLEDs based on mixed bromide and chloride perovskites is very low, around 1.7%, due to poor film morphology, phase separation, high trap density, and imbalanced charge injection etc. Here, we propose to effectively control the grain size and morphology of mixed Br-Cl perovskite films by incorporation of long-chain organic ammonium halides which can self-assemble at the three-dimension perovskite grain surface, and to effectively suppress halide migration and phase separation by chemical modification of the long-chain ammonium halides. Surfactants with ammonium group and/or P=O bonds will be used to passivate the traps caused by halides and lead, aiming to make high quality and luminescent mixed Br-Cl perovskite films. The energy levels of electron and hole transporting layer will be optimized to improve the injection current balance, EQE, and stability. We aim to fabricate stable blue PeLEDs with EQE above 15% that emission at around 450 nm, and promote the application of PeLED in the field of solid state lighting and flat panel display.

近年来，有机无机杂化钙钛矿材料因其优异的光电特性成为材料和光电子器件领域的研究热点。其带隙可连续调节、荧光效率高等特性使其在LED领域有巨大应用潜力。然而，由于发蓝光的溴氯混合钙钛矿LED存在薄膜形貌难控制、相分离、缺陷密度高、电子空穴注入不平衡等问题，外量子效率（EQE）仅为1.7%。本研究将充分利用长链氨基分子和钙钛矿晶粒之间自组装的特性，来有效调控晶粒尺寸和薄膜形貌；并将优化长链氨基分子结构，使包附在晶粒表面的长链氨基分子更好的阻止离子移动和相分离。本研究将针对钙钛矿中的缺陷类型，综合采用含有氨基和P=O键的表面活性剂来有效钝化卤素和铅导致的缺陷，以此获得高质量和高荧光效率的溴氯混合钙钛矿薄膜。然后通过优化电子和空穴传输层的能级位置提高蓝光钙钛矿LED的注入电流平衡、EQE和稳定性。最终制备出EQE超过15%，发光波长在450nm左右的蓝光钙钛矿LED，推动其在显示和照明中的应用。

发蓝光的溴氯混合钙钛矿LED中存在薄膜形貌难控制、相分离、缺陷密度高、电子空穴注入不平衡等问题，这限制了它在LED领域的巨大应用潜力。在本项目研究中，我们通过长链氨基分子和钙钛矿晶粒之间的自组装、混合溶剂配制过饱和前驱液等方法有效调控薄膜的表面形貌及晶粒尺寸，制备出高质量的钙钛矿薄膜。通过氧气钝化薄膜中的缺陷、调控薄膜中过量卤化物浓度等方法抑制钙钛矿薄膜中的离子移动。我们还发现锡基钙钛矿或锡掺杂的钙钛矿LED在工作条件下不存在离子移动现象，通过研究不同锡掺杂比例下钙钛矿的离子移动情况确定了离子移动的活化能阈值为0.65 eV。为了钝化钙钛矿薄膜中不同类型的缺陷，包括晶界处铅或卤素悬挂键导致的缺陷，我们合成了双重钝化剂对钙钛矿薄膜中的不同缺陷进行了全方位的钝化。另外，我们研究了空穴传输层的导电性对器件性能的影响，并通过使用高电荷迁移率的空穴传输层制备出了高EQE、高亮度的钙钛矿LED。. 在基金委的资助下，发表包括Nature Photonics，Nature Communication，Advanced Materials等权威期刊在内的SCI论文16篇，授权的国内发明专利1项，实质审查的专利2项，完成了项目设定的考核目标。