Dopant-induced interactions in spiro-OMeTAD: Advancing hole transport for perovskite solar cells

Organic semiconductors play a crucial role in the architecture of thin-film electronic devices, particularly as hole transport layers in solar cells. These materials are essential for overcoming significant barriers to improving device lifetime and performance. Among these materials, the small molecule 2,2 ',7,7 '-tetrakis[N,N-di(4methoxyphenyl)amino]-9,9 '-spirobifluorene, known as spiro-OMeTAD, has been instrumental in the development of high-efficiency perovskite solar cells (PSCs) for over a decade. During this time, the additives used to tune the properties of spiro-OMeTAD have undergone significant evolution. Based on current literature, this review examines how interactions in the doping of spiro-OMeTAD have influenced the performance of PSCs, discusses alternatives for future development by highlighting their advantages and limitations, and provides insights into whether spiro-OMeTAD remains the best hole transport material for n-i-p structured PSCs.