Cost-effective dopant-free star-shaped oligo-aryl amines for high performance perovskite solar cells

Cost effective imidazole-based star-shaped oligo(arylamines) were easily prepared in good yields via the reaction of one precursor containing two or more aldehydes with a dione compound having two arylamines. High performance perovskite (MAPbI₃) solar cells with a conventional cell configuration were fabricated using these compounds as dopant-free hole transport materials. The best solar-to-electricity conversion efficiency reached ∼17.5%, which surpassed that based on LiTFSI/t-BP doped spiro-OMeTAD. The cell also exhibited much better temporal stability than the standard cell of LiTFSI/t-BP doped spiro-OMeTAD, as no hydrophilic dopants are needed.