Fig. 4.

a Measured J–V curves and b external quantum efficiency spectra for the perovskite photovoltaic devices with the highest performance. Photovoltaic parameters of the reference device and the PSC made with a 300-nm moth-eye PDMS film are shown in the inset of a. c J–V curves for reference perovskite photovoltaic and devices made with 300-nm and 1000-nm moth-eye PDMS films. d Measured enhancement of photovoltaic parameters in PSCs made with 300-nm and 1000-nm moth-eye PDMS films relative to the reference device