Over 1000 nm photoresponse with cyclopentadithiophene-based non-fullerene acceptors for efficient organic solar cells

Abstract

Non-fullerene acceptors have a pivotal role in the progress of organic solar cells (OSCs). Though, optical characteristics most of NFAs is quite limited within the range of 600–900 nm, limiting the short-circuit density (Jsc) of the OSCs devices. To address this issue, we have designed nine different C-shaped cyclopentadithiophene (CPDT)-based acceptor–donor-acceptor (A-D-A) structured NFAs for OSCs. To this end, various end-cap functional units have been used to further modify the reference molecule (C0) to improve the optoelectronics and photophysical characteristics of these materials. For this, various advanced quantum mechanical density functional theory (DFT) and time dependent (TD-DFT) approached used to explore the hidden potential of these materials (R, CA1-CA9). The characterizations associated with frontier molecular orbitals (FMOs), transition density Matrix (TDM) analysis, open-circuit voltages (Voc), electron-hole reorganizational energies, fill factor and optical properties of all the investigated molecules are calculated at DFT and TD-DFT-B3LYP/6-31G. In addition to all these calculations the PTB7-Th:C5 complex study (D:A) has also been investigated to check out the charge-transfer from donor polymer (PTB7-Th) to NFA C5 at the D:A interface. The results of these investigations reveal that all the designed A-D-A molecules (C1-C9) with electron-rich core and with electron-deficient end-capped acceptors are perfect for efficient tuning of optical and electrical parameters. With such approach, we can design desired photovoltaic materials by tuning their FMO energy levels, binding energy, and reorganizational energies, Voc, fill factor and absorption maxima characteristics. Therefore, these deigned materials (C1-C9) are highly recommended for synthesis to develop an efficient OSCs. And, this approach could be use effectively to design desire properties materials for the future development of an efficient photovoltaic materials.