Achieving efficient exciton dissociation and high power conversion efficiency (PCE) becomes a great challenge when the open circuit voltage (VOC) of organic photovoltaic (OPV) reaches the upper limit value of...

Compared with other all-inorganic/organic–inorganic hybrid solar cells, the large voltage loss (V loss) of organic photovoltaic (OPV) cells, especially the nonradiative voltage loss (ΔV nonrad), limited the further improvement of performance. Although A-DA′D-A-type Y-series nonfullerene acceptors (NFAs) largely improve the power conversion efficiencies (PCEs) to 18%, the open-circuit voltage (V OC) of this kind of material was still restricted to below 1.0 V. Herein, we designed and synthesized a narrow bandgap (E g = 1.41 eV) acceptor BTA77 with an A-DA′D-A-type backbone containing a nonhalogenated terminal group to achieve high electroluminescence efficiency and high V OC. Combined with the nonhalogenated polymer PBDB-T with a conjugated thiophene side chain, BTA77 realized a V OC of 0.944 V, a V loss of 0.552 V, and a PCE of 13.75%, which is one of the highest PCEs based on nonhalogenated A-DA′D-A-type acceptors with V OC > 0.9 V. After further blending with the nonhalogenated donor polymer PBT1-C with a conjugated phenyl side chain, the V OC increases to 1.021 V with a super low ΔV nonrad of 0.14 V owing to the greatly improved electroluminescence external quantum efficiency (EQEEL) of 4.42 × 10–3. Our results indicate that there is still a large room to decrease the ΔV nonrad and increase V OC by synergistic molecular engineering of p-type polymers and n-type small molecules.

Organic photovoltaics (OPVs) are a promising technology for indoor low-energy-consumption portable electronic equipment.