Optimization of PTB7-FTh-Based Organic Photovoltaic Devices Using Blade Coating: Influence of Solvent, Acceptor...

In this study, we report the synthesis and characterization of a fluorinated polymer, PTB7-FTh, designed as a donor material for organic photovoltaic (OPV) devices. The polymer structure is based on PTB7-Th, with the addition of fluorine substituents to enhance molecular interactions and energy level alignment. OPV devices were fabricated using a scalable blade coating technique under an ambient atmosphere, utilizing different solvent systems, donor-to-acceptor ratios, and acceptor materials (Y6 and PC₇₁BM). The effects of active layer thickness and thermal annealing on device performance were also investigated. The optimized ternary blend system, incorporating PTB7-FTh, Y6, and PC₇₁BM (1:1.6:0.2), exhibited a power conversion efficiency (PCE) of 5.03%, with an open-circuit voltage (V _oc) of 0.76 V, a short-circuit current density (J _sc) of 13.39 mA cm^-2, and a fill factor (FF) of 49.22%. The system PTB7-FTh:Y6:PCBM, 12 mg mL^-1 in chloroform, 1:1.6:0.2, pretreatment heating at 80 °C, named CF system, demonstrated superior charge transport and light absorption properties, particularly after thermal annealing, which led to efficiency improvements. The use of o-xylene as a processing solvent proved advantageous for scalability while maintaining competitive device performance compared to those fabricated under inert conditions. This study highlights the potential of PTB7-FTh as a promising donor material and underscores the importance of solvent selection, acceptor composition, and processing conditions for advancing the scalability of OPV technology.