Elevated Stability and Efficiency of Solar Cells via Ordered Alloy Co-Acceptors

Power conversion efficiency (PCE) and long-term stability are the two key parameters of photovoltaic devices to meet standards for commercial use. In this Letter, an ordered alloyed co-acceptor by incorporating PC61BM and COi8DFIC is obtained. This ordered alloy structure increases the light absorption by producing a shoulder peak at 935 nm and improves electron mobility from 1.51 × 10–5 to 8.91 × 10–4 cm2 V–1 s–1 by PC61BM interacting with the end group of COi8DFIC and connecting adjacent COi8DFIC molecules. Consequently, the PCE is enhanced from 10.80 to 14.22%, enhancement of about 32%. Even further, the device stability is improved due to the fact that the alloy fixes the morphology of the active layer. After keeping for 7200 h, about 10 months, the PCE of those solar cells is retained at 13.2%, corresponding to a PCE loss of only 5.7%, while the PCE loss in the binary control device is up to 33.3%.