Fig. 2: EL spectra of perovskite LEDs under above- and sub-bandgap voltages.

a, b EL spectra of a FPI perovskite LED driven at different bias above and below the bandgap voltage. c, d EL spectra of a NFPI perovskite LED driven at different bias above and below the bandgap voltage. e, f EL spectra of a PCPB perovskite LED driven at different bias above and below the bandgap voltage.