Redox-Improved Self-Assembled Monolayers for Inverted Perovskite Solar Cells
Meng Yuan, Y. John Wang, Zhe Liu, Jinyuan Zhang, Shucheng Qin, Minchao Liu, Zekun Chen, Yao Zhao, Jing Li, Xiaojun Li, Lei Meng, Yongfang Li
Abstract
Inverted perovskite solar cells (pero-SCs) utilizing nickel oxide (NiOx)/self-assembled monolayer (SAM) as a hole transport layer (HTL) have demonstrated high power conversion efficiency (PCE). However, variations in the valence states of NiOx on the surface create complexity in the growth of a high-quality SAM HTL. To address these challenges, a new SAM molecule MeOF-4SHCz is synthesized and utilized to target the Ni3+-rich regions on the NiOx substrate. A redox reaction occurs at the interface and the oxidation product of MeOF-4SHCz forms a new S−O−Ni bonding at the Ni3+-rich regions. The application of the combined SAMs of MeOF-4SHCz and the regular SAM MeOF-4PACz can improve the overall coverage and uniformity of the SAM layer on NiOx. As a result, the optimized inverted pero-SCs based on this redox-improved (ROI)-SAM HTL of MeOF-4SHCz/MeOF-4PACz = 4:1 (w/w) achieve a high PCE of 26.5% (certified as 26.28%) and improved stability with T90 > 1000 hours. Variations in the valence states of nickel oxide hinder the growth of a uniform self-assembled monolayer (SAM). Here, authors develop a SAM with the oxidized product forming S−O−Ni bond at Ni3+-rich regions, achieving maximum device efficiency of 26.5% in operationally stable perovskite solar cells.