Figure 3. External Quantum Efficiencies (EQEs) (re-plotted from representations such as in Figure 2) shown as a function of the incident laser power for the different active layer thicknesses of (a) PTB7:PC70BM and (b) PCDTBT:PC70BM blends.

The EQEs were normalized to 100% and the laser power to the 1 sun equivalent power to visualize the bimolecular recombination losses at the short-circuit conditions. This methodology allows one to quantify the photocarrier bimolecular recombination losses in actual solar cells under close-to-operational conditions. Figure (c) shows the recombination losses estimated from the Figures (a) and (b) and plotted as a function of the active layer thickness.