Peripheral donor engineering of indolo[3,2-b]indole-based hole transporting materials for highly efficient perovskite solar cells
摘要
Among promising next-generation photovoltaic technologies, perovskite solar cells (PSCs) have gained significant attention. The integration of hole-transporting materials (HTMs) is indispensable for achieving efficient charge extraction in high-performance PSCs. Tuning the peripheral substituents of HTMs represents a viable strategy for boosting the performance of PSCs. In this work, a series of novel small-molecule HTMs are modified by replacing the terminal alkyl chains with planarized end-groups. The impacts of donor engineering on their photophysical, electrochemical, and molecular electrostatic potential properties, as well as reorganization energies, density of states, quantum chemical descriptors, transition density matrices, binding energies, and hole transport capabilities, have been systematically explored via quantum chemical computations. The planarized end-groups not only modulate the electronic structure to facilitate better energy level alignment with the perovskite active layer, but also contribute to enhance intermolecular packing. Compared to the reference IDIDF, the molecules TIDIDF and OIDIDF exhibit enhanced light-harvesting peaks, which can be attributed to intramolecular charge-transfer effects. Notably, the molecule OIDIDF displays a lower reorganization energy and a larger HOMO–HOMO orbital overlap integral (S) of 1.17 × 10−2 eV. The improved π–π stacking interactions and greater orbital overlap for the dimers of molecular OIDIDF contribute to stronger intermolecular electronic coupling, thereby promoting their superior hole mobility. This research highlights a promising pathway for developing economical small-molecule HTMs aimed at advancing the performance of perovskite solar cells.