Improving the Performance of Hole Transport Layer‐Free Carbon Perovskite Solar Cells by Controlling the Crystallization of the RbCl‐Based Perovskite Films

Additive engineering is a critical strategy for enhancing the quality of perovskite thin films and the photovoltaic performance of perovskite solar cells (PSCs). Herein, rubidium chloride (RbCl) was incorporated to regulate the properties of perovskite thin films and their devices. Experimental results demonstrate that RbCl improves the crystallinity of perovskite films, increases grain size, and enables the formation of compact, uniform perovskite films, which effectively suppress interfacial charge recombination. Consequently, the power conversion efficiency (PCE) of PSCs was boosted from 13.18% (control) to 17.08% (RbCl‐modified). Additionally, the RbCl‐modified devices exhibited enhanced stability, retaining 92% of their initial efficiency after 700 h of storage. This work highlights RbCl as a simple yet effective additive for simultaneously enhancing the PCE and operational stability of hole transport layer‐free carbon‐based PSCs.