Design of High-Performance Mixed-Dimensional Perovskite by Incorporating Different Halogenated Cesium Sources

Although two-dimensional perovskites have attracted much attention due to their high humidity stability, their poor photovoltaic performances have severely obstructed their further development. As a simple and effective method, the regulation of composition can significantly improve the performances of perovskite solar cells (PSCs). Hence, to enhance the PCE of prepared mixed-dimensional (MD) perovskite based on ammonium iodide, three Cs sources containing different halogens were introduced to regulate the components. Through the introduction of Cs+, the photovoltaic performances and long-term stability of MD PSCs are dramatically improved, and the MD perovskite device with CsI achieves great photovoltaic performance with the PCE of 19.14%. After the incorporation of Br– and Cl–, the performances of MD perovskites with CsBr and CsCl are further enhanced. In particular, MD perovskite with CsCl has a superior vertical growth crystal structure, flat surface morphology, faster charge transfer, slower carrier recombination, and markedly reduced defect density; thus, the obtained device displays the highest PCE, reaching 19.81%. More importantly, these Cs-doped MD perovskites exhibit a significantly improved humidity, heat, and UV light stability. The results highlight the applicability and potential advantages of MD perovskite materials in photovoltaic applications and provide a new research direction for realizing long-term, stable, and efficient PSCs.