Enhancing efficiency for additive–free blade–coated small–molecule solar cells by thermal annealing

Abstract

Blade coating was successfully applied to realise high-efficiency small-molecule organic solar cells (OSCs) with a solution-processed active layer comprising a small organic molecule DR3TBDTT with a benzo[1,2–b:4,5–b′]dithiophene (BDT) unit as the central building block as the donor and [6,6]–phenyl–C71–butyric acid methyl ester (PC71BM) as the acceptor. Using chloroform as the solvent, a DR3TBDTT/PC71BM blend active layer without an additive was effectively formed through blade coating. The power conversion efficiency (PCE) of small organic molecule solar cells was enhanced by 3.7 times through thermal annealing at 100 °C. This method produces OSCs with a high PCE of up to 6.69%, with an open circuit voltage (Voc) of 0.97 V, a short-circuit current density (Jsc) of 12.60 mA/cm2, and a fill factor (FF) of 0.55.