High Efficiency Nitride Green LEDs with Built-in PL Color Converter

The well-known "Green gap" issue related to LEDs efficiency significantly limits the full color applications in both display and lighting. In order to solve this problem, in this study, a new green LED structure is proposed, which includes a regular short wavelength MQWs for the electroluminescence (EL) emission, and a green photoluminescence (PL) color conversion region, so called EP-LED. The shorter wavelength EL region is responsible for carrier injection and recombination, which suffers from a much weaker QCSE, and the longer wavelength PL region is responsible for high quantum efficiency color conversion, whose strain field has no effect on carrier injection. With this novel hybrid active-region design, the green EP-LED shows more than 30% improved WPE over the conventional one at current density of 50 A/cm
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, and 1/3 suppressed blueshift in wavelength in the current range of 1 mA to 100 mA, as well as the much-reduced efficiency Droop. It is very encouraging that the green or long wavelength EP-LEDs will meet many new needs in future display and lighting applications.