铅卤钙钛矿材料中热载流子动力学研究

In recent years, the rapid improvement of the power conversion efficiency(PCE) of lead halide perovskite solar cells has attracted great attention of the scientific community. In the past few years, the PCE of these kinds of solar cell has increased from 3.81% in 2009 to over 23%, approaching the Shockley-Queusser limit efficiency (33%). Understanding the physical mechanism is an important factor to further improve its efficiency. In the process of photoelectric energy conversion, the relaxation process of photoinduced hot carriers to the band edge is the key factor affecting the efficiency of solar cells, and the generation of long-lived hot carriers in lead-halide perovskite is very helpful to its high efficiency. In this project, we plan to study the relaxation process of hot carriers in lead-halide perovskite materials by using time-dependent non-adiabatic molecular dynamics based on first principles calculations. Considering different factors such as large polaron, hot phonons, and spin-orbit coupling, we will study the effects of phonon excitation, electro-acoustic coupling, molecular orientation and spin-orbit coupling on hot carriers and reveal the real mechanism of long-life hot carriers. The physical mechanism of the generation provides a reasonable design scheme for further improving the photoelectric conversion efficiency.

近年来，铅卤钙钛矿太阳能电池光电转换效率的快速提升引起了科学界对这类材料的极大关注。在过去的几年里，此类太阳能电池的光电转换效率由2009年的3.81%提升到了超过23%，快速逼近Shockley-Queusser极限效率（33%），理解其中的物理机制是进一步提高其效率的重要因素。在光电能量转换过程中，光激发热载流子向带边的弛豫过程是影响太阳能电池效率的关键因素，而铅卤钙钛矿中长寿命热载流子的产生对其高效率有很大的帮助。在本项目中，我们计划利用基于第一性原理的含时非绝热分子动力学研究铅卤钙钛矿材料中热载流子的弛豫过程，综合考虑大极化子、热声子、自旋轨道耦合等不同因素，研究声子激发、电声耦合、分子取向、自旋轨道耦合对热载流子的影响，揭示长寿命热载流子产生的物理机制，为进一步提高其光电转化效率给出合理的设计方案。

通过本项目的执行，我们发展了动量空间载流子非绝热分子动量学新方法，能够有能力在动量维度研究载流子的动力学过程。提出了载流子自旋保护机制，有助于通过缺陷的磁性调控，助于与新型光催化材料的开发。发现了钙钛矿体系动力学缺陷，并阐明其在第三代光伏材料，有希望突破单结太阳能电池的Shockley–Queisser 33%的效率极限，为钙钛矿光伏进一步提高光伏效率提供了理论基础。另外，通过MAPbI3的界面体系，阐明界面偶极对电荷动力学影响的重要性。与此类似，二维钙钛矿层间极化也极大地影响载流子的动力学过程。除此之外，我们在表面氢键网络，缺陷钝化等方面取得突破。