Screening the effects of additional donors, numbers, and positions of π-spacers on perylene-based sensitizers for dye-sensitized solar cell applications

Perylene-based metal-free organic sensitizers are investigated computationally through density functional theory and time-dependent density functional theory for the ground-state and excited-state geometries using the B3LYP/6-311G(d,p) basis set. In the present work, six novel organic sensitizers (DPP-1 to DPP-6) based on perylene donors having diphenylamine as an auxiliary donor are chosen. The sensitizers have cyanoacrylic acid as an acceptor and thiophene and cyanovinyl as π-spacers. The aim of the work is to enhance the Power Conversion Efficiency (PCE) of the dye-sensitized solar cell by having different numbers and positions of the π-spacers and the addition of an auxiliary donor in the sensitizers. The frontier molecular orbital analysis results have the lowest value of HOMO–LUMO energy gaps, which helps to improve the electron injection and electron regeneration processes. Natural bonding orbital analysis reveals the electron-donating and electron-accepting abilities of the sensitizers. Accordingly, the change of position and increased number of π-spacers show that the HOMO–LUMO gap value decreases, the redshift to the absorption spectrum increases, and the light-harvesting efficiency improves. The results reveal that the highest number of π-spacers improves the PCE of the solar cell.