Organic-inorganic halide perovskites have shown promise for solar cells with performance approaching that of commercially available devices. These devices could transform the solar energy landscape, given the promise for low-cost manufacturing of flexible devices. Further advances require a deeper understanding of structure-property relationships. This project plans to study the fundamental properties of perovskites. The focus will be on spin-orbit coupling, which connects optical, electrical, and magnetic properties. These studies will combine materials processing, device engineering, and dynamic measurements. The goal is to achieve a deeper understanding of these materials and advance the performance of perovskite solar cells. The project will impact graduate and undergraduate students through outreach and new curriculum. The PI will also recruit and involve students from underrepresented groups in science and engineering.
The proposed project will experimentally investigate spin-orbital coupling (SOC) effects in organic-inorganic hybrid halide perovskite solar cells ranging from 3D to 2D designs. The recent success of perovskite solar cells stems from the high absorption coefficient, efficient dissociation of excited states, and superior carrier transport that simultaneously occur within spin-orbital coupling framework. However, in-depth fundamental studies are timely needed to further advance the research and development of perovskite solar cells by revealing deeper structure-property relationships in both excited state and carrier dynamics. The objective of this project is to understand the SOC effects under doping, structural ordering, and external stimuli. The goal of this research is to reveal the underlying mechanisms to tune SOC effects, Rashba effects, and spin mixing towards providing innovative mechanisms to further advance photovoltaic functionalities in organic-inorganic hybrid halide perovskites. This project plans to achieve three critical goals: (i) reveal innovative mechanisms of doping-tunable SOC, (ii) explore SOC effects on direct/indirect band transitions through Rashba effect, and (iii) elucidate SOC effects on spin mixing between dark and bright states, in hybrid halide perovskites ranging from 3D to 2D designs. The proposed research will be performed by integrating three major interdisciplinary efforts from materials processing, device engineering, and experimental measurements, to explore SOC effects. The materials processing effort will prepare both 3D and 2D perovskites with different polarizations and structural symmetries/asymmetries to provide a fundamental platform to explore SOC effects. The device engineering effort will prepare state-of-the-art perovskite solar cells from 3D to 2D structures. The experimental measurements will include magnetic field effects, light polarization-modulated photocurrent/photoluminescence, time-resolved photoluminescence spectroscopy, and pump-probe transient absorption to reveal underlying mechanisms towards controlling SOC effects in hybrid halide perovskites ranging from 3D to 2D designs upon introducing doping, structural ordering, and external stimuli. Overall, the project will elucidate the key factors of controlling SOC effects, Rashba effects, and spin mixing towards fundamentally advancing perovskite photovoltaic devices.
This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.
