High-Efficiency All Polymer Solar Cell with a Low Voltage Loss of 0.56 V

Reducing voltage loss, namely, <i>V</i><sub>loss</sub>, has been demonstrated to be an effective way to improve the efficiencies of photovoltaic devices, and power conversion efficiencies (PCEs) exceeding 10% have been reported in non-fullerene based polymer solar cells (PSCs) with <i>V</i><sub>loss</sub> value lower than 0.6 V. However, for all polymer solar cells (APSCs), the PCEs lag far behind the non-fullerene PSCs with organic small molecular acceptors. And there have been no successful examples of high-efficiency APSCs along with low <i>V</i><sub>loss</sub> values so far. Here, we reported APSCs that demonstrated a high efficiency of 6.66% simultaneously with a small voltage loss of 0.56 V by using a new polymer PBDT-DFQX1 as donor and N2200 as acceptor. Notably, when PBDT-DFQX1 is combined with a small molecular acceptor (SMA) O-IDTBR, the relative SMA based PSC exhibited a higher PCE of 8.76% also with a low voltage loss of 0.56 V. These results indicated that PBDT-DFQX1 would be a promising polymer donor material in photovoltaic device application, and the strategy by minimizing the voltage loss to improve the photovoltaic efficiencies is still valid for APSCs.