Paek, S.Zimmermann, I.Gao, P.Gratia, P.Rakstys, K.Grancini, G.Nazeeruddin, Mohammad KhajaRub, Malik AbdulKosa, Samia A.Alamry, Khalid A.Asin, Abdullah M.2016-09-102016-09-102016-09-10201610.1039/c6sc01478jhttps://infoscience.epfl.ch/handle/20.500.14299/129234WOS:000382488500056Donor-pi-bridge-donor type oligomers (D-pi-D) have been studied intensively as active materials for organic optoelectronic devices. In this study, we introduce three new D-pi-D type organic semiconductors incorporating thiophene or thienothiophene with two electron-rich TPA units, which can be easily synthesized from commercially available materials. A thorough comparison of their optoelectronic and structural properties was conducted, revealing the strong influence of the extent of longitudinal pi-bridge conjugation on both the solid structure of the organic semiconductive materials and their photovoltaic performance when applied as hole transporting materials (HTM) in perovskite solar cells. Single-crystal measurements and time-resolved photoluminescence (TRPL) studies indicate that these coplanar donor-pi-donor type HTMs could be promising alternatives to state-of-the-art spiro-OMeTAD, due to the multiple intermolecular short contacts as charge transporting channels and efficient charge extraction properties from the perovskite layer. The optimized devices with PEH-9 exhibited an impressive PCE of 16.9% under standard global AM 1.5 illumination with minimized hysteretic behaviour, which is comparable to that of devices using spiro-OMeTAD under similar conditions. Ambient stability after 400 h revealed that 93% of the energy conversion efficiency was retained for PEH-9, indicating that the devices had good long-term stability.text::journal::journal article::research article