Cation disorder engineering yields AgBiS2 nanocrystals with enhanced optical absorption for efficient ultrathin solar cells

Strong optical absorption by a semiconductor is a highly desirable property for many optoelectronic and photovoltaic applications. The optimal thickness of a semiconductor absorber is primarily determined by its absorption coefficient. To date, this parameter has been considered as a fundamental material property, and efforts to realize thinner photovoltaics have relied on light-trapping structures that add complexity and cost. Here we demonstrate that engineering cation disorder in a ternary chalcogenide semiconductor leads to considerable absorption increase due to enhancement of the optical transition matrix elements. We show that cation-disorder-engineered AgBiS2 colloidal nanocrystals offer an absorption coefficient that is higher than other photovoltaic materials, enabling highly efficient extremely thin absorber photovoltaic devices. We report solution-processed, environmentally friendly, 30-nm-thick solar cells with short-circuit current density of 27 mA cm(-2), a power conversion efficiency of 9.17% (8.85% certified) and high stability under ambient conditions.

Automated summary

This study investigates the enhanced optical absorption of a ternary chalcogenide semiconductor through engineering cation disorder, which enables the development of highly efficient extremely thin absorber photovoltaic devices. The experimental results demonstrate that colloidal nanocrystals with engineered cation disorder show a significantly higher absorption coefficient compared to other photovoltaic materials, offering a promising solution for environmentally friendly and solution-processed solar cells.