Optimizing hole transport efficiency in perovskite solar cells by structural modeling of 1,4-dihydropyrrolo[3,2-b]pyrroles with various donors: a DFT approach.

Hole transport materials (HTMs) are crucial in controlling charge dynamics in perovskite solar cells (PSCs), notably in processes such as interfacial charge separation and electron recombination. Currently, a series of 1,4-dihydropyrrolo[3,2-b]pyrrole (DHPP) based HTMs (PSR and PSD1-PSD7) possessing a D-π-D architecture was designed through molecular engineering with various heterocyclic donors. The photovoltaic and optoelectronic characteristics of the designed derivatives were investigated using the M06 functional with the 6-311G (d,p) basis set in DFT/TD-DFT approaches. All compounds displayed energy gaps in the range of 3.113-3.678 eV, with absorption spectra in the range of 420.5 to 444.3 nm. Frontier molecular orbital (FMO) investigations demonstrated an efficient intramolecular charge transfer (ICT) from the DHPP core to terminal donors. The significant charge transfer was further supported by the transition density matrix maps and the density of states. All designed chromophores revealed lower exciton binding energy values (E b = 0.310-0.772 eV), showing higher exciton dissociation rates with enhanced charge transfer. A benchmark analysis with spiro-OMeTAD used as a standard in HTM studies demonstrated that the engineered chromophores exhibited good hole transport performance. These results indicate that structural modeling of organic chromophores with heterocyclic donors can effectively tune their photovoltaic properties, making them promising candidates for use as efficient HTMs.