Photovoltaic investigation of CPDT based small molecule for BHJ OSC devices

In recent years, Bulk heterojunction organic solar cells (BHJ OSCs) based small molecules take leading position of industrialization for their considerable opto-electronic properties and uncomplicated fabrication process. Materials based on cyclopentadithiophene (CPDT) have been widely used thanks to their interesting structural and electronic characteristics. Here we report a combined experimental and theoretical investigation of a CPDT-based material namely 6,6′-(2,5-bis (hexyloxy)-1,4-phenylene) bis(2-methyl −4H- cyclopenta [2,1-b:3,4-b'] dithiophen-4-one) (CPDT-alt-BHP) as donor small molecule in a BHJ OSC. The synthesized molecule shows a rigid and planar structure with small band gap energy. The electronic properties have been investigated by means of Density Functional Theory (DFT) at B3LYP/6-31g(d) level of theory. The studied molecule displayed an optical absorption in the visible region with $\lambda\_\text{max}=404$ nm. Transition density matrix (TDM) plot was carried out to get insight into the hole-electron coherences at the first excited state. The photovoltaic parameters of CPDTBHP:[70]PCBM system were simulated using wxAMPS software. The designed BHJ OSC exhibited respectable fill factor (FF) of 81.13%, short-circuit current density (Jsc) of 6.089 mA cm-2 and power conversion efficiency (PCE) of 4.922%. The studied compound offers significant structural and optoelectronic properties that could be enhanced via judicious molecular tuning.