Stable and highly efficient perovskite solar cells: Doping hydrophobic fluoride into hole transport material PTAA
Chao Yu, Buyue Zhang, Chen Chen, Jintao Wang, Jian Zhang, Ping Chen, Chuannan Li, Yu Duan
Abstract
Perovskite solar cells (PSCs) have rapidly developed in the past few years, with a record efficiency exceeding 25%. However, the long-term stability of PSCs remains a challenge and limits their practical application. Many high-performance PSCs have an n-i-p device architecture employing 4-tert-butylpyridine (t-BP) and bis(trifluoromethane)sulfonimide lithium salt (Li-TFSI) as bi-dopants for the hole-transporting layer (HTL). However, the hygroscopicity of Li-TFSI and low boiling point of t-BP negatively impact the moisture stability of these PSC devices. Herein, we report the use of the fluorine-containing hydrophobic compound tris(pentafluorophenyl)phosphine (35FP) as a dopant for poly[bis(4-phenyl)(2,4,6-trimethylphenyl)amine] (PTAA). With better hydrophobicity and stability than undoped PTAA, a PSC device containing 35FP-doped PTAA demonstrated improved charge transport properties and reduced trap density, leading to a significant enhancement in performance. In addition, the long-term stability of a 35FP-doped PTAA PSC under air exposure without encapsulation was demonstrated, with 80% of the initial device efficiency maintained for 1,000 h. This work provides a new approach for the fabrication of efficient and stable PSCs to explore hydrophobic dopants as a substitute for hydrophilic Li-TFSI/t-BP.