Morphological Control for High Performance, Solution‐Processed Planar Heterojunction Perovskite Solar Cells

TLDR

Organometal trihalide perovskite solar cells have achieved the highest efficiencies in mesostructured composites, yet thin solid films could reach comparable performance in a simple planar heterojunction configuration. The authors control film morphology by varying processing conditions to maximize perovskite surface coverage, which is essential for attaining the highest photocurrents. Optimized solution‑based film formation yields planar heterojunction perovskite solar cells with 11.4 % power conversion efficiency, the first >10 % result for fully thin‑film, solution‑processed devices without a mesoporous layer.

Abstract

Organometal trihalide perovskite based solar cells have exhibited the highest efficiencies to‐date when incorporated into mesostructured composites. However, thin solid films of a perovskite absorber should be capable of operating at the highest efficiency in a simple planar heterojunction configuration. Here, it is shown that film morphology is a critical issue in planar heterojunction CH 3 NH 3 PbI 3‐ x Cl x solar cells. The morphology is carefully controlled by varying processing conditions, and it is demonstrated that the highest photocurrents are attainable only with the highest perovskite surface coverages. With optimized solution based film formation, power conversion efficiencies of up to 11.4% are achieved, the first report of efficiencies above 10% in fully thin‐film solution processed perovskite solar cells with no mesoporous layer.