Dopant-Free Hole-Transport Material with a Tetraphenylethene Core for Efficient Perovskite Solar Cells

A hole-transport material (HTM), 1,1,2,2-tetrakis[4-(3,6-di-tert-butyl-9H-carbazol-9-yl)phenyl]ethene (TTBCPE), was prepared straightforwardly and employed in the fabrication of perovskite solar cells (PSCs). The investigated HTM with tetraphenylethene as the core and tert-butylcarbazole as terminal units was synthesized in two steps from commercially available and cheap raw materials. The devices based on TTBCPE without the use of any dopants and additives exhibited a power conversion efficiency (PCE) of 12.65%, which is comparable to 14.46% obtained by using devices based on 2,2',7,7'-tetrakis(N,N-di-p-methoxyphenylamino)-9,9-spirobifluorene (p-doped spiro-OMeTAD). Importantly, the device based on TTBCPE showed a higher stability than devices based on doped spiro-OMeTAD if stored under ambient conditions. In this regard, this easily synthesized and dopant-free system paves a new way to develop low-cost HTMs.