D–A–D-\nand A–A–D-Type\nCyanopyridone Derivatives as a New Class of Hole-Transporting Materials\nfor Perovskite Solar Cells

The present study focused on the development and characterization\nof four new low-cost hole-transporting materials (HTMs), <b>ZZ01</b>, <b>DJ01</b>, <b>PR01</b>, and <b>PM01</b>, designed\nbased on the concepts of donor–acceptor–donor (D–A–D)\nor acceptor–acceptor–donor (A–A–D) for\napplication in perovskite solar cells (PSCs). These molecules were\nsystematically synthesized and extensively analyzed for their structural,\nphotophysical, electrochemical, thermal, density functional theory\n(DFT), and charge transport properties. The absorption and emission\nspectra of the synthesized molecules exhibited bands in the ranges\nof 380–393 and 457–495 nm, respectively, and demonstrated\nappropriate energy levels, with a band gap ranging from 2.78 to 2.91\neV, which matches well with the requirements for PSCs. The thermogravimetric\nanalysis confirmed their thermal stability up to 230–418 °C,\nwhich is crucial for device durability. Theoretical calculations via\nDFT and TD-DFT corroborated the experimental findings, validating\nthat the HOMO–LUMO energy levels and reorganization energies\nwere conducive to effective hole transport. Xerographic time-of-flight\nmeasurements indicated superior hole mobility of 2 × 10<sup>–5</sup> cm<sup>2</sup>/V·s for <b>ZZ01</b>, highlighting its\npotential as an efficient HTM. Overall, this research underscores\nthe promising candidacy of synthesized π-conjugated molecules\nas HTMs in PSCs, offering a pathway toward enhancing device performance\nand commercial viability in the field of renewable energy.