Molecular Engineering of Simple Carbazole-Triphenylamine Hole Transporting Materials by Replacing Benzene with Pyridine Unit for Perovskite Solar Cells

Four carbazole-triphenylamine hole transporting materials (HTMs) with a pyridine or benzene on the N of carbazole have been designed and developed. The molecular structures on their photophysical, electrochemical, thermal, as well as photovoltaic properties in perovskite solar cells (PSCs) are comprehensively analyzed. It is noted that the pyridine-contained compounds show bathochromic spectra response, slightly lower HOMO level, and higher thermal stability than their benzene-contained counterparts. Photoluminescence study indicates that the molecule with a pyridine unit possess better hole extraction properties on the perovskite/HTM interface. When used in PSCs, pyridine-contained HTMs exhibit higher efficiency and better stability than benzene-contained HTMs. Moreover, the PSCs based on the pyridine-contained HTM exhibit a promising power conversion efficiency of 18.45% with good light-soaking and long-term stability, which is even better than that of conventional spiro-OMeTAD under the same conditions. Therefore, the results provide a promising strategy to design and develop novel HTM molecules for efficient and stable PSCs.