Poly(N,N′‐bis‐4‐butylphenyl‐N,N′‐biphenyl)benzidine as Interfacial Passivator for Dopant‐Free P3HT Hole Transport Layer‐Based Perovskite Solar Cell in Regular Mesoscopic Architecture

The best‐recorded performance of perovskite‐based solar cells (PSCs) in regular mesoscopic architecture is generally associated with the use of the common 2,2′,7,7′‐tetrakis[ N,N‐ di(4‐methoxyphenyl)amino]‐9,9′‐spirobifluorene (Spiro‐OMeTAD). However, the need for lithium‐based hygroscopic dopants hinders the chemical and environmental stability of the devices. This work presents a passivated stable PSC device based on a dopant‐free poly(3‐hexylthiophene) (P3HT) hole transport layer. By introducing a poly( N,N′‐ bis‐4‐butylphenyl‐ N,N′ ‐biphenyl)benzidine (polyTPD) interlayer at the perovskite/P3HT interface, the parameters of the low‐performance pristine P3HT‐based cells are improved. This introduction leads to optimizing the P3HT film morphology, interfacial defects, and charge extraction, along with a significant suppression of interfacial recombination and enhancement of the cell power conversion efficiency (PCE) from 7% to 10.65%. Further, an improvement is observed in open‐circuit voltage and the fill factor, increasing from 0.912 to 0.95 V and from 59.2% to 61.1%, respectively. Moreover, the noncapsulated passivated PSC devices exhibit higher operational stability. Examinations show that devices in a dark controlled environment (10–15% humidity) can retain 82% of their initial PCE for 450 h, and 73% of their initial PCE when thermally stressed at 60 °C temperature under ambient conditions (25–35% humidity) for 264 h.