Non-fullerene organic solar cells based on a small molecule with benzo[1,2-c:4,5-c’]dithiophene-4,8-dione as π-bridge

In this work, we designed and synthesized a new acceptor-π-donor-π-acceptor (A-π-D-π-A) type small molecule (SM) donor material, BBDDR, based on thienyl-substituted benzo[1,2-b:4,5-b’]dithiophene (BDT-T) as the electron-donating core, the benzo[1,2-c:4,5-c’]dithiophene-4,8-dione (BDD) along with two thiophene units as π-bridge and rhodanine as the end group. BBDDR exhibits a strong absorption in the visible range of 300–700 nm with an optical bandgap (E_g ^opt) of 1.79 eV, deep-lying HOMO energy level of −5.40 eV and high hole mobility of 1.1 × 10⁻³ cm² V⁻¹ s⁻¹. The organic solar cells (OSCs) based on BBDDR: IDIC exhibited an optimized power conversion efficiency (PCE) of 7.8% with a high open-circuit voltage (V_oc) of 1.01 V, a short circuit current density (J_sc) of 14.6 mA cm⁻², and a fill factor (FF) of 53% under the illumination of AM 1.5G, 100 mW cm⁻².