Two acetylene-bridged molecules, built by grafting phthalimides on thienoisoindigo (TII) and diketopyrrolopyrrole (DPP) blocks, have been synthesized, characterized and evaluated as electron acceptor materials in air-processed inverted organic solar cells.

New three-dimensional hole-transporting materials (HTMs) based on either 9,9′-spirobifluorene (SBF) or spiro-[cyclopenta­[1,2-b:5,4-b′]­dithiophene-4,9′-fluorene] (SDTF) core have been synthesized. All three HTMs, namely, SBFCz2, SDTFCz2, and SDTCz2F, are end-capped with two peripheral 3,6-dimethoxydiphenylaminyl-carbazole (CzDMPA) units. The HTMs behave as molecular glasses with glass transition temperature (T g) close to or higher than that of the reference HTM Spiro-OMeTAD. Thermal and optoelectronic properties strongly depend upon the nature of the bridging core unit between the two CzDMPA units. The two fluorene-bridged molecules SBFCz2 and SDTFCz2 exhibit similar properties. On the contrary, SDTCz2F, where the CzDMPA units are bridged to the cyclopentadithiophene ring, displays lower highest occupied molecular orbital/lowest unoccupied molecular orbital energy levels and smaller band gaps. Upon doping of the HTM layer in perovskite solar cells, in spite of a much lower hole mobility, SDTCz2F leads to the highest power conversion efficiency (16.4% compared to 14.5 and 14.3% for SBFCz2 and SDTFCz2, respectively).