Overcoming the Performance Limitation of Cs₂AgBiBr₆ Double Perovskites Using Bifacial Photovoltaic Design

Abstract

Cs2AgBiBr6 is an encouraging example of perovskites which shows potential toward the development of more stable and nontoxic photoactive materials. However, relative to its necessarily large optical thickness, the material has substantially deficient electron diffusion lengths, which limit its photovoltaic efficiency. Herein, this problem is solved by designing a double‐sided semitransparent architecture for a Cs2AgBiBr6‐based photovoltaic material. In this case, the bifacial design deliberately creates an imbalance between the electron and hole densities, resulting in asymmetric lengths of carrier conduction near their respective transporting layers. Coupled optoelectronic simulations suggest that the use of the bifacial architecture results in an improvement of around 34% in the efficiency, from 3.47% to 4.64%, compared to the standard configuration. This method is effective to improve electron conduction in Cs2AgBiBr6, which is typically severe compared to its hole conduction. Finally, the strength of the correlation between the power conversion efficiency of the bifacial architecture and the diffusion length, asymmetric ratio of electron and hole conduction, and light albedo factor are explored. The results highlight some ways to improve the photovoltaic efficiency of Cs2AgBiBr6 above 8%, for instance, through tuning the surface recombination and band alignment between Cs2AgBiBr6 and the hole‐transporting layer.