Hybrid organic-inorganic perovskites (HOIPs) exhibit long charge carrier diffusion length and high optical absorption coefficient; as a result, they are very attractive photovoltaic materials for high performance solar cells. Understanding the dynamics of photo-induced charge carriers in HOIPs is essential to enhance the performance of these new materials. Since slower carrier relaxation enhances the quantum yield in photovoltaic energy conversion, there is urgent need to understand hot carrier relaxation in HOIPs to allow more efficient harvesting of high-frequency lights. Relaxation of hot carriers in HOIPs occurs in the picosecond time scale and this process can be investigated theoretically using time dependent methods to guide future experimental research by providing atomistic insights into the relaxation process. Here, in this project, we will carry out ab initio non-adiabatic molecular dynamics simulations to study non-radiative relaxation dynamics of charge carriers (electrons and holes) in different HOIPs. We will further compare the radiative relaxation dynamics of charge carriers in both purely inorganic and hybrid perovskites to discover the ubiquitous role of organic ligands in hot carrier relaxation. Expected outcome from this project involves theoretical estimates of the cooling time of hot carriers in different HOIPs to help us understand non-adiabatic carrier-carrier and carrier-phonon coupling. Such understanding would help the HOIP field design and optimize ionic species in HOIPs to develop more efficient single-junction photovoltaic cells that can harvest hot carriers and break the theoretical Shockley-Queisser limit. This computational materials project is built based on our numerous research breakthroughs in understanding the structural, transport, electronic, and phonon properties in emerging HOIPs (Science Advances, 2017, 3 (12), EAAQ0208; Nature Communications, 2017, 8, 16086; Angewandte Chemie International Edition, 2017, 56 (31), 9018; ACS Nano, 2017, 11 (1), 1073; ACS Nano, 2016, 10 (12), 11044; ACS Nano, 2016, 10 (10), 9720; Advanced Functional Materials, 2016, 26 (29), 5297).
The postdoc will receive training in ab initio non-adiabatic molecular dynamics simulations, electronic structure and optical property calculations, and Born-Oppenheimer molecular dynamics simulations, in addition to publishing in high impact-factor journals. Formal training's in career skills include academic job searching, grant proposal writing, and oral presentation at major research conferences.