In this presentation, I will first introduce the basic principle of photovoltaic (PV) materials and devices. Once the fundamental aspects have been laid out, I will follow with a detail discussion of perovskite (PVSK) PV technologies.<br/>Perovskite solar cell is the major research in my group. The characteristic grain boundaries (GBs) and the surface of the polycrystalline perovskite films were found to contribute to the trap states and further act as vulnerable spots to trigger environmental degradation. In this presentation, I will report our recent understanding of methods for manipulation of the defects in perovskite solar cells via grain boundary engineering and surface passivation. 1. Crystallization kinetics of the perovskite layer was controlled by the engineering of intermediate phases, which resulted in a significant enhancement in crystallinity with reduced defects. The inevitable defects at GBs were effectively passivated by additives. Significant enhancement in photoluminescence lifetime supported the effective passivation of defects at the perovskite layer. As a result, the PCE exceeding 22% was achieved for a planar heterojunction perovskite solar cell. Thanks to the passivated GBs, the device demonstrated significantly enhanced stability. 2. Surface trap-mediated non-radiative charge recombination is a major limit to achieving high-efficiency metal-halide perovskite photovoltaics. The ionic character of the perovskite lattice has enabled molecular defect passivation approaches via interaction between functional groups and defects. The chemical environment of a functional group that is activated for defect passivation was systematically investigated with theophylline, caffeine, and theobromine. When N-H and C=O were in an optimal configuration within the molecule, hydrogen-bond formation between N-H and I assisted the primary C=O binding with the antisite Pb defect to maximize surface-defect binding. A power conversion efficiency of 23.5% (steady-state PCE 22.6%) of the photovoltaic device was demonstrated with theophylline treatment.<br/>I will also report our progress on perovskite tandem solar cells. A high-performance perovskite tandem solar cell was achieved via engineering of the interconnecting junction, where certified power conversion efficiency over 22% was demonstrated.

Strategies toward highly efficient perovskite solar cells

ACS Spring Meeting 2021

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.