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A new crystallizable low band gap conjugated copolymer BTT ‐ DTFFBT is designed and synthesized. The polymer solar cells based on BTT ‐ DTFFBT: PC71BM photoactive layer are fabricated and characterized. It is found that after combined treatment of 1 vol % 1 ‐ chloronaphthalene (CN) additive and thermal annealing at 180 °C for 10 min, the device shows a power conversion efficiency (PCE) of 5.61% and good thermal stability. [ABSTRACT FROM AUTHOR]

Nickel acetate (Ni(Ac) 2 ) was successfully introduced to the low band-gap system for the first time and incorporated as the anode interlayer in conventional polymer solar cells (PSCs). For PBDT-TS1/PC 71 BM system, the device based on as-prepared Ni(Ac) 2 performs a lower power conversion efficiency (PCE) of 6.26% in comparison to that of PEDOT:PSS-based device (6.56%). After appropriate pre-bias treatment, the device efficiency rapidly increases to 7.27%, which is 11% and 16% higher than that of PEDOT:PSS- and as-prepared Ni(Ac) 2 -based device, respectively, due to the suppressed charge recombination and enhanced hole transport at anode interface. More importantly, device with pre-bias treated Ni(Ac) 2 as anode interlayer exhibits significantly improved lifetime in N 2 atmosphere. The Ni(Ac) 2 -based PSCs could maintain almost 85% of its original PCE after 200 h, while PEDOT:PSS-based PSCs only retains 60% of its original efficiency. This work demonstrates that the low-cost Ni(Ac) 2 is an ideal anode interlayer material, which could simultaneously improve the device efficiency and stability, to replace the widely used and high-cost PEDOT:PSS. [ABSTRACT FROM AUTHOR]