Investigating the impact of end-capped acceptor alterations to dimethyl fluorene-based hole transporting material for perovskite solar cells

Abstract

Hole-transporting materials (HTMs) could boost the proficiency of third generation-perovskite solar cells since they have ultrafast charge mobility that improves optoelectronic and photovoltaic attributes. Five new H-shaped molecules were sketched using thiophene bridged, end-capped acceptor alteration on a dimethyl fluorene core-based molecule. Planarity measurements, absorption spectra, frontier molecular orbitals (FMOs), excitation energy (Ex), density of states (DOS), molecular electrostatic potentials (MEPs), transition density matrix (TDM), exciton binding energy, interaction coefficient, hole-electron overlap, open circuit voltage, fill factor, and power conversion efficiency were analyzed via DFT/MPW1P9W1/6-31G (d,p) for evaluating performance of perovskite solar cells. All newly sketched molecules with an A-π-D-π-A skeleton exhibited outstanding optoelectronic properties, including broader absorbance (563–740 nm) in chlorobenzene, indicating better solution processing. Lower band gaps (2.08–2.72 eV) than reference (3.78 eV) indicated efficient electron density transfer. Increased open-circuit voltage (1.55–2.02 eV) along with lower reorganization energies of the electron (0.043249–0.122527 eV) and hole (0.108105–0.148322 eV) lead to effective charge transport capabilities. Higher dipole moments indicated suitable film fabrication. A higher fill factor (0.9166–0.9325) and power conversion efficiency (34.31–45.49 %) led to an improved performance. Concisely, all the newly sketched molecules showed redshifted absorbance, narrower band gaps, deeper HOMO energies, improved charge transfer, higher softness, and smaller hardness values when compared to ZR, which confirms their superiority as future dopant-free HTM for PSCs.