Characterization of Ag₃BiI₆ Rudorffite Absorber for Ambient-Air-Stable, Lead-Free and Efficiency Solar Cells Through Scanning Kelvin Probe Analyzer

Perovskite solar cells, renowned for their exceptional power conversion efficiency (PCE), hold promise as a sustainable and renewable energy solution. However, the utilization of lead-based absorbers in these cells raises significant concerns due to the toxic nature of lead. Their stability in ambient conditions is also a challenge should be overcome for their further development. To address these issues, we investigated the feasibility of adopting a novel lead-free material, Ag₃BiI₆ rudorffite absorber, as an alternative active layerto replace the conventional lead-based perovskite absorber.<b>[1,2]</b> Ag₃BiI₆ rudorffite absorber layer is prepared by using a large scalable thermal-assisted doctor blade coating methodAs a novel light absorber layer, realizing the localized work function of Ag₃BiI₆helps to optimize the energy level in its device. In this study, we employed a scanning Kelvin probe analyzer (KP Technology, SKP 5050), equipped with red, green, and blue LED light sources with a total power of 300 mW, to measure the constant potential difference (CPD) and investigate the local work function of the Ag₃BiI₆ rudorffite absorber. The scanning Kelvin probe analyzer, a highly sensitive and non-contact scanning probe technique, allows us to assess the light response of the absorber layer by measuring the light-induced CPD under different wavelengths. The CPD of the absorber layer serves as an indicator of the light response of Ag₃BiI₆ rudorffite, providing insights into its performance when exposed to various incident light. With assistance of Kelvin probe analyzer, we optimized the energy level alignment between the carrier transporting layers and the Ag₃BiI₆ rudorffite absorber layer, resulting in an improved PCE of doctor-bladed devices from 2.06% to 2.77%. Taking advantages of band alignment, these devices retain 90% of their initial PCE over 3,000 hours in ambient without any unencapsulation. Moreover, the scalability of our approach is also demonstrated and the device with an active area of 1.00 cm² achieves a PCE of 2.03%.<b>[3]</b> In summary, our study highlights the potential of Ag₃BiI₆ rudorffite as a viable substitute for lead-based perovskite absorbers in solar cells. Its superior environmental safety, stability, and scalability make it an attractive candidate for the development of sustainable energy technologies.<br/><br/><b>Refereces</b><br/><b>[1] </b>Kai-Chi Hsiao, Yen-Fu Yu, Ching-Mei Ho, Meng-Huan Jao, Yu-Hsiang Chang, Shih-Hsuan Chen,Yin-Hsuan Chang, Wei-Fang Su, Kun-Mu Lee*, and Ming-Chung Wu*, "Doping Engineering of Carrier Transporting Layers for Ambient-Air-Stable Lead-Free Rudorffite Solar Cells Prepared by Thermal-Assisted Doctor Blade Coating", 2023, <b><i>Chemical Engineering Journal</i></b>, 451, 138807.<br/><b>[2] </b>Ming-Chung Wu*, Qian-Han Wang, Kai-Chi Hsiao, Shih-Hsuan Chen, Ching-Mei Ho, Meng-Huan Jao, Yin-Hsuan Chang, and Wei-Fang Su, "Composition Engineering to Enhance the Photovoltaic Performance and to Prolong the Lifetime for Silver Bismuth Iodide Solar Cell", 2022, <b><i>Chemical Engineering Journal Advances</i></b>, 10, 100275.<br/><b>[3] </b>Ming-Chung Wu*, Ruei-Yu Kuo, Yin-Hsuan Chang, Shih-Hsuan Chen, Ching-Mei Ho, and Wei-Feng Su, "Alkali Metal Cation Incorporated Ag₃BiI₆ Absorbers for Efficient and Stable Rudorffite Solar Cells", 2021, <b><i>Oxford Open Materials Science</i></b>, 1, itab017.