*Article* **Cesium Doping for Performance Improvement of Lead(II)-Acetate-Based Perovskite Solar Cells**

**Min-Seok Han 1, Zhihai Liu 2, Xuewen Liu 1, Jinho Yoon 1 and Eun-Cheol Lee 1,3,\***


**Abstract:** Lead(II)-acetate (Pb(Ac)2) is a promising lead source for the preparation of organolead trihalide perovskite materials, which avoids the use of inconvenient anti-solvent treatment. In this study, we investigated the effect of cesium doping on the performance of Pb(Ac)2-based perovskite solar cells (PSCs). We demonstrate that the quality of the CH3NH3PbI3 perovskite film was improved with increased crystallinity and reduced pinholes by doping the perovskite with 5 mol% cesium. As a result, the power conversion efficiency (PCE) of the PSCs was improved from 14.1% to 15.57% (on average), which was mainly induced by the significant enhancements in short-circuit current density and fill factor. A PCE of 18.02% was achieved for the champion device of cesium-doped Pb(Ac)2-based PSCs with negligible hysteresis and a stable output. Our results indicate that cesium doping is an effective approach for improving the performance of Pb(Ac)2-based PSCs.

**Keywords:** perovskite solar cells; performance improvement; lead acetate; cesium doping

**Citation:** Han, M.-S.; Liu, Z.; Liu, X.; Yoon, J.; Lee, E.-C. Cesium Doping for Performance Improvement of Lead(II)-Acetate-Based Perovskite Solar Cells. *Materials* **2021**, *14*, 363. https://doi.org/10.3390/ma14020363

Received: 12 December 2020 Accepted: 11 January 2021 Published: 13 January 2021

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