Solar energy is one of the most promising green technologies and could enable humankind to meet its future energy needs in a sustainable manner. The development of high performance, low cost and environmentally friendly solar cells is therefore critical for our energy security. One of the most promising new class of materials for solar energy is metal halide perovskites. The power conversion efficiency of solar cells made from such perovskites has witnessed an unprecedented rate of increase. Despite their outstanding performance, perovskites have poor stability and are prone to photo-decomposition due to ion migration. There are also serious issues with their environmental compatibility as the highest performing perovskite solar cells contain lead, a highly poisonous metal. Furthermore, lead iodide, a common decomposition product of these materials, is carcinogenic. In the face of these challenges, it is necessary to identify and develop high performing and lead free perovskites that are intrinsically stable under light irradiation and when exposed to the environment. This project will investigate solar cells based on chalcogenide perovskitesâ€”an alternative to metal halide perovskites typically used in solar cells. These materials are free of lead and use a chalcogen such as sulfur, which could result in superior stability. This project could lead to a new class of high performance and environmentally stable solar cells and photodetectors with transformative impacts.
A number of fundamental science and device engineering issues will be addressed in this project in order to enable the successful deployment of chalcogenide perovskite based materials in high performing optoelectronic devices such as photo-detectors and solar cells. These include: (1) understanding the nature of defects in these materials, and how they affect the dark current, band structure, mid gap states, and carrier lifetimes. The chalcogenide perovskite material growth conditions will be carefully controlled, to minimize such defects; (2) Alloying strategies to optimize the band gap of chalcogenide perovskite based materials will be theoretically predicted using first-principles density functional theory calculations. Such alloying will also be experimentally realized to demonstrate chalcogenide perovskite materials with optimized bandgaps; (3) State of the art machine learning tools (guided by ab initio calculations and experiments) will be used to systematically screen the entire family of chalcogenide perovskite materials in order to find the optimal material and alloying combination; (4) Photo-detector and solar cell devices constructed using the optimized chalcogenide perovskite material will be developed and systematically characterized to demonstrate the proof of concept. The above tasks will together provide the fundamental knowledge that is needed to demonstrate high performing, environmentally stable and lead free optoelectronic devices using the family of chalcogenide perovskite materials.
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.