Quantum Chemical Design of D–π–A-Type Donor Materials for Highly Efficient, Photostable, and Vacuum-Processed Organic Solar Cells

Fullerene-free donor materials are receiving more and more attention from the scientific community due to their high power conversion efficiencies (PCEs) and large visible-light-harvesting capabilities. Herein, five new molecules (ZDM1–ZMD5) with D–π–A-type skeletons are efficiently designed and theoretically characterized. These newly tailored molecules can improve the PCEs of vacuum-processed organic solar cells (OSCs). End-capped donor modifications of DTDCPTT-2CN (R) are done with well-organized end-capped donor units. Density functional theory at MPW1PW91 method along with 6-31 G(d,p) level is utilized to calculate various photovoltaic (PV), physiochemical, and optoelectronic properties of these novel theoretically planned molecules. Different geometric parameters are also computed for the studied molecules. A narrow bandgap (E _g = 1.52–1.93 eV) with redshifting (λ _max = 589–614 nm) in the absorption spectrum is observed for ZDM1–ZDM5. Further, low excitation (E _x) and binding energies (E _b) offer high current charge density (J _sc) along with good PCE. A blend study of ZDM3/PC₆₁BM is also carried out to explore the charge transfer behavior of the designed molecules. Finally, more than 10% PCE is predicted (theoretically) using the Scharber model. To sum up, results of different analyses suggest that these theoretically modeled molecules are efficient aspirants for highly stable and efficient vacuum-processed OSCs.