Fig. 6. (a) The J–V characteristics of the best performing OPVs for TPA-PTZ-BDP, PTZ-TPA-BDP and N-PTZ-BDP molecules for their optimized blend ratio with PC₇₁BM. (b) EQE spectra of the above devices. (c) Steady state fluorescence spectra and (d) decay kinetics of a neat PC₇₁BM film and of the optimised photovoltaic blends containing the PC₇₁BM : BODIPY ratio shown, recorded after excitation at 515 nm and normalised to the absorbed excitation power. Kinetics were obtained by integrating fluorescence spectra from 680–850 nm. The vertical scale is logarithmic.