A Brief Overview of Poly(3-Hexylthiophene) as a Hole Transport Material for Perovskite Solar Cell

Perovskite solar cells (PSCs) have been widely developed and are now moving toward large-scale commercialization. Hole transporting material (HTM) is an important part of PSCs, where it plays a crucial role in facilitating hole extraction to the anode and blocking electrons from passing through it. Although 2,2',7,7'-Tetrakis(N,N-di-p-methoxyphenylamine)-9,9'-spirobifluorene (Spiro-OMeTAD) and polytriarylamine are the commonly explored HTMs in PSCs, they need unstable hygroscopic ion dopants and additives to enhance their hole mobility, which can deteriorate the performance/stability of the device. Benefiting from the low-cost synthesis, well batch-to-batch stability, excellent hole mobility and good moisture resistance of the poly(3-hexylthiophene) (P3HT), it has then been used as an alternative HTM in PSC applications. However, the energy level mismatch and the poor interface contact between the perovskite material and P3HT have limited hole transfer to the anode, thus affecting the device performance and stability. In this review, the research progress of the P3HT HTM through interface modification, doping strategy, P3HT derivatives, etc. is summarized to address the aforementioned problems. Finally, this review also provides guidance for further improving the efficiency and stability of P3HT-based PSCs.