以无机CsPbBr3钙钛矿单晶薄膜为增益介质的绿光垂直腔面发射激光器研究

Recently, the newly emerging metal halide perovskite materials have increasingly received our attention due to their potential applications in luminescence field. At present, tri-phosphor light-emitting diodes (LEDs) based on perovskites have been successfully fabricated. In addition, optically pumped stimulated emission behaviors have also been achieved in perovskite polycrystalline films and micro/nanostructures. However, electrically pumped lasing action based on perovskites has not been reported yet. This is mainly due to the difficulties in acquiring high-quality perovskite single-crystal thin films, and the existence of grain boundaries and defects greatly increases the probability of nonradiative recombination. Besides, there are obvious differences between perovskite-based laser diodes and LEDs. On the one hand, the realization of electrically driven lasing requires a reasonable regulation of carrier injection and confinement processes. On the other hand, a high-quality optical resonator has to be introduced into the device structure. Under such circumstance, we propose a space-confined solution-processed strategy to prepare high-quality inorganic CsPbBr3 perovskite single-crystal thin films, which are employed as the lasing gain medium. An Al component gradually changed p-AlxGa1-xN layer with polarization effect, and a n-MgZnO layer with adjustable band-gap are used as the carrier-supplying layers to improve the carrier injection process. In addition, an AlN/GaN distributed Bragg reflector is introduced to form the optical resonator to support the oscillation and amplification of photons in the gain medium. By using the designed device structure, the realization of green vertical-cavity surface-emitting laser diodes with an all-inorganic heterostructure could be expected. This project will provide theoretical and experimental foundations for the fabrication of novel perovskite-based laser diodes.

近两年，金属卤化物钙钛矿材料在发光领域的潜在应用引起了人们的广泛关注。目前，基于钙钛矿材料的三基色发光二极管（LED）已可成功制备，而且人们相继在钙钛矿多晶薄膜和微纳米结构中实现了光泵浦受激发射现象。但基于钙钛矿材料的电泵浦激光器件未见报道。这主要是由于高质量钙钛矿单晶薄膜制备困难，晶粒边界和缺陷的存在大大增加了载流子发生非辐射复合的几率；此外，钙钛矿激光器件结构不同于LED，电泵浦激光的产生既要求对载流子的注入和限制行为进行合理调控，又需要引入高品质的光学谐振腔。针对此问题，本项目提出利用空间限域法制备高质量CsPbBr3单晶薄膜作为增益介质，采用梯度p-AlxGa1-xN极化势垒层和带隙可调的n-MgZnO层优化载流子的注入过程，并通过制备分布式布拉格反射镜形成光学谐振腔，从而研制出全无机异质结构的钙钛矿绿光垂直腔面发射激光器。该项目的开展将为新型钙钛矿激光器的研制提供理论和实验依据。

近几年，金属卤化物钙钛矿材料在发光领域的潜在应用引起了人们的广泛关注。目前，基于钙钛矿材料的三基色发光二极管（LED）已可成功制备，而且人们相继在钙钛矿多晶薄膜和微纳米结构中实现了光泵浦受激发射现象。但基于钙钛矿材料的激光器件未见报道。这主要是由于高质量钙钛矿单晶薄膜制备困难，晶粒边界和缺陷的存在大大增加了载流子发生非辐射复合的几率；此外，钙钛矿激光器件结构不同于LED，电泵浦激光的产生既要求对载流子的注入和限制行为进行合理调控，又需要引入高品质的光学谐振腔。由此，本项目提出利用无机钙钛矿单晶薄膜作为增益介质，优选载流子传输层来平衡载流子的注入过程，并通过引入光学谐振腔来制备基于钙钛矿材料的激光器。在材料制备方面，申请人利用空间限域法和双温区化学气相生长技术，成功制备出高质量无机钙钛矿单晶薄膜和尺寸可调的立方钙钛矿微尺度单晶。基于钙钛矿单晶薄膜，通过构建垂直谐振腔结构，实现了纵模间隔一致的激射模式；基于钙钛矿微尺度单晶，利用其自形成的回音壁微腔，实现了单光子、双光子、三光子激光输出，并且三光子回音壁模激光可在400 K下连续稳定工作。基于环保、安全等因素的考虑，申请人开展了异价金属替位策略成功制备出多种无铅钙钛矿发光材料，发光波长可以在385−640 nm范围内连续可调，从真正意义上摆脱了“铅依赖”，并通过变温荧光光谱、瞬态吸收光谱和第一性原理计算对材料的发光物理过程进行了阐明。进一步，采用上述无铅钙钛矿材料作为发光层，申请人成功制备出电驱动的紫光、蓝光、黄光LED，器件的工作稳定性大大优于传统铅基体系。上述工作为“绿色”、低成本钙钛矿发光器件的制备研究提供了解决方案。. 项目执行中发表了SCI论文45篇，含第一/通讯作者论文40篇，影响因子大于10.0的文章17篇，ESI高被引论文7篇；合著英文专著（章节）3部；申请发明专利10项，已授权6项；培养博士研究生1人，硕士研究生3人。