Environmentally affable and highly efficient donor material based on cyclopentadithiophene (CPDT) framework for remarkable organic solar cells

Abstract

The quantum chemical exploration of highly conjugated D-π-A type molecules based on cyclopentadithiophene (CPDT) core is anticipated to recommend novel organic materials for efficient organic solar cells (OSCs). Five new conjugated molecules (C1–C5) were designed by drafting of reference CR through thiophene bridged end caped acceptors and their geometric, as well as optoelectronic properties, were investigated at MPW1PW91/6-31G (d,p) functional. All the newly tailored chromophores (C1–C5) proclaimed lower energy gap values (ranging from 1.95 to 2.19 eV) than the reference CR (3.18 eV). TD-DFT calculations of all the newly designed molecules revealed higher λmax in the range 500–514 nm than the reference CR (483.2 nm) in dichloromethane solvent. Lower excitation energies (1.79–1.94 eV) and higher dipole moment (4.84–18.37 D) for all the drafted compounds (C1–C5) than reference CR were observed which proclaimed efficient charge transfer. Simulations of global reactivity parameters like hardness, chemical potential, softness and electrophilicity manifested all these molecules (C1–C5) to be reactive and thermally stable. The small values of reorganization energies for electron and hole exhibited high electron-hole mobilities and low charge recombination. The power conversion efficiency (PCE) parameters were simulated by scaling the HOMO of designed molecules acting as a donor with LUMO of PC61BM acceptor. All the designed molecules (C1–C5) demonstrated high open circuit voltage (0.67–0.92 V) than the reference (0.49 V) which is favorable for enhancement of PCE. Also, the higher values of fill factor (FF) ranging from 0.8417 to 0.8677 for newly designed chromophores increased the PCE than reference CR (0.8015). The results demonstrated the suitability of these donor molecules designed by deliberated technique, opening a new path for the development of donor's contributors to OSCs and may prove efficient materials for fabrication of future OSCs.