Efficient ternary organic photovoltaic cells with better trade-off photon harvesting and phase separation by doping DIB-SQ

Photon harvesting and phase separation can be synergistically optimized by using ternary strategy with appropriate DIB-SQ-doped Si-PCPDTBT:PC₇₁BM as active layer. The power conversion efficiency (PCE) of ternary organic photovoltaic cells (OPVs) exhibits an increasing and then decreasing trend dependent on the increase in DIB-SQ doping ratio. The PCE of OPVs was increased from 5.52% to 6.18% by doping 3 wt% DIB-SQ while keeping the donor/acceptor doping weight ratio at 1:1.5. The PCE improvement can be attributed to the better trade-off between photon harvesting and phase separation in the ternary active layers. The degree of phase separation strongly influences energy or charge transfer between donors and charge transport in the ternary active layers. The dynamic process between donors was investigated according to J-V curves of cells without acceptor under light illumination. Experimental results fully confirm that this ternary strategy should have a brilliant future due to about 12% PCE improvement compared with Si-PCPDTBT:PC₇₁BM-based binary OPVs.