Dithienopyrrol‐Cored Hole Transport Material Enabling Over 21% Efficiency Dopant‐Free Perovskite Solar Cells

• Published in: Advanced functional materials 2019-09, Vol.29 (38)
• Main Authors: Yin, Xinxing, Zhou, Jie, Song, Zhaoning, Dong, Zihao, Bao, Qinye, Shrestha, Niraj, Sandip Singh Bista, Ellingson, Randy J, Yanfa Yan, Tang, Weihua
• Format: Article
• Language: English
• Subjects: Commercialization; Dopants; Energy conversion efficiency; Energy levels; Hole mobility; Materials science; Perovskites; Photovoltaic cells; Polymethyl methacrylate; Solar cells; Transport
• ISSN: 1616-301X; 1616-3028
• DOI: 10.1002/adfm.201904300

Dopant‐free hole transport materials (HTMs) are essential for commercialization of perovskite solar cells (PSCs). However, power conversion efficiencies (PCEs) of the state‐of‐the‐art PSCs with small molecule dopant‐free HTMs are below 20%. Herein, a simple dithieno[3,2‐b:2′,3′‐d]pyrrol‐cored small molecule, DTP‐C6Th, is reported as a promising dopant‐free HTM. Compared with commonly used spiro‐OMeTAD, DTP‐C6Th exhibits a similar energy level, a better hole mobility of 4.18 × 10−4 cm2 V−1 s−1, and more efficient hole extraction, enabling efficient and stable PSCs with a dopant‐free HTM. With the addition of an ultrathin poly(methyl methacrylate) passivation layer and properly tuning the composition of the perovskite absorber layer, a champion PCE of 21.04% is achieved, which is the highest value for small molecule dopant‐free HTM based PSCs to date. Additionally, PSCs using the DTP‐C6Th HTM exhibit significantly improved long‐term stability compared with the conventional cells with the metal additive doped spiro‐OMeTAD HTM. Therefore, this work provides a new candidate and effective device engineering strategy for achieving high PCEs with dopant‐free HTMs.