Efficient energy transfer and smooth charge transport via second donor as third component materials in ternary polymer solar cells

In this paper, ternary polymer solar cells (PSCs) consisting of two blend donors (FTAZ and PTB7-Th) and one acceptor (N3) with similar highest occupied molecular orbital (HOMO) energy levels, different absorption peaks and cascading lowest unoccupied molecular orbital (LUMO) energy levels are built. The ternary PSCs achieve higher photovoltaic performance and better thermal stability compared to the FTAZ:N3 binary PSCs. The A medium wavelength absorption FTAZ polymers and long wavelength absorption PTB7-Th polymers as the blend donor, and near-infrared wavelength absorption N3 as the acceptor. The optimize ternary PSCs exhibit a maximum power conversion efficiency of 15.65%, with an open-circuit voltage of 0.852 V, a short-circuit current of 25.25 mA cm−2, and an FF of 72.5%. This performance of device is attributed to more efficient exciton dissociation and suppression of charge recombination within ternary films. The ternary PSCs also show good crystallinity and surface morphology at room temperature and after thermal annealing for 20 h at 70 °C, which is attribute to the better thermal stability of the ternary PSCs.