Fig. 1: Conceptual design of colour perception using a single device.
From: Spectrum projection with a bandgap-gradient perovskite cell for colour perception
a Spectral diagram. b Scheme of the average photon energy. c Colour perception using an optoelectronic device with bandgap-gradient semiconductors, in which one output signal is determined only by the total photon flux (I1 = f (φ)), and the other is dependent on both the total photon flux and average photon energy (\(I_2 = {\mathrm{f}}\left( {\overline {\varepsilon _\varphi } ,\varphi } \right)\)). d Scheme of human visual colour perception in terms of hue (value 0–1). e Correlation between hue and average photon energy.
