Electrothermal and optical impacts on two-dimensional colour gamut properties of red–green–blue LED devices

Existing colour gamut metrics for solid-state lighting and displays are typically three-dimensional descriptions that do not explicitly capture how chromatic boundaries change under electrical and thermal operating conditions. Consequently, there is a lack of quantitative understanding of two-dimensional (2D) colour gamut behaviour of RGB LED devices as a function of driving current and device temperature. This work bridges the gap by experimentally mapping the 2D colour gamut boundaries of RGB LED pixels across current and temperature ranges and proposing a model that links operating conditions to observed gamut shifts. These operating conditions are optimized by simultaneously maximizing the 2D colour gamut area and the wall-plug efficiency via a multi-objective scaled merit function. Furthermore, integrating of RGB LEDs with an added white LED (RGBW system) enabled dynamic correlated colour temperature regulation from 2000 K to 9000 K under the tested conditions, via adjustment of the white-LED drive current with compensatory RGB currents and device temperature. The 2D colour gamut variation exhibits a strong dependence on white-LED compensation, shifting from minor to significantly under specified conditions. Given this strong dependence, a novel multi-physical model integrating electrical, thermal and optical characteristics was developed to accurately predict gamuts and luminous fluxes.