Nonfullerene Ternary Organic Photovoltaics with Long-Wavelength Light-Absorption Guest Donor Materials to Improve Photovoltaic Performance

In order to achieve efficient organic photovoltaics (OPVs), a ternary strategy was adopted with the efficient long-wavelength light-absorption donor material of PSBTBT as the third component material (guest donor) and the D18-Cl:BTP-eC9 binary film as the host photoactive layer, which facilitates the acquisition of absorption spectra complementary to those of D18-Cl and BTP-eC9. The PL spectrum of D18-Cl was covered by the absorption spectrum of PSBTBT, which further supports the energy transfer from D18-Cl to PSBTBT. In addition, the addition of a small amount of PSBTBT to the D18-Cl:BTP-eC9 binary film slightly changed the bulk and surface morphology of the photoactive layer, while appropriate phase separation size and a smooth surface could be achieved for both the D18-Cl:BTP-eC9 binary film and the optimized ternary film. Thus, with 10% PSBTBT as the third component material (D18-Cl/PSBTBT/BTP-eC9 ratio of 0.9:0.1:1.2), the ternary OPV shows a higher power conversion efficiency (PCE) of 17.35%. The improvement of photovoltaic performance is due to the short-circuit current density (JSC) enhancement from 24.65 to 26.23 mA cm–2, even though the open-circuit voltage (VOC) weakly decreased from 0.905 to 0.900 V. This work provides an effective method to find a guest polymer that matches the host binary photoactive layer, broadens the absorption spectrum, and provides efficient energy transfer within both donor materials.