Dopant‐Free Polymer HTM‐Based CsPbI<sub>2</sub>Br Solar Cells with Efficiency Over 17% in Sunlight and 34% in Indoor Light
Zhanglin Guo, Ajay Kumar Jena, Izuru Takei, M. Ikegami, A. Ishii, Youhei Numata, Naoyuki Shibayama, Tsutomu Miyasaka
Abstract
Abstract To abate the issue of moisture‐assisted phase transition of CsPbI 2 Br, caused by hygroscopic dopants used in the hole‐transporting material (HTM), developing dopant‐free HTMs is necessary. In this work, a new polymer, PDTDT, is developed as a dopant‐free HTM for CsPbI 2 Br solar cells, and the device performance and stability are systematically compared with cells employing dopant‐free P3HT. CsPbI 2 Br solar cells using PDTDT show an efficiency of 17.36% with V OC of 1.42 V and FF of 81.29%, which is one of the highest values for CsPbI 2 Br cells. Moreover, a record‐high efficiency of 34.20% with V OC of 1.14 V under 200 lux indoor light illumination and efficiency of 14.54% (certified efficiency of 13.86%) for a 1 cm 2 device under one sun are accomplished. Importantly, PDTDT shows superior/comparable device stability to P3HT, promising its potential to be an alternative to popular doped Spiro‐OMeTAD and P3HT HTM.