White light emitting diodes with super-high luminous efficacy

Abstract

We fabricated three types of high luminous efficacy white light emitting diodes (LEDs). The first was a white LED with a high luminous efficacy (ηL) of 249 lm W−1 and a high luminous flux (ϕv) of 14.4 lm at a forward-bias current of 20 mA. This ηL was approximately triple that of a tri-phosphor fluorescent lamp (90 lm W−1). The blue LED used as the excitation source in this white LED had a high output power (ϕe) of 47.1 mW and a high external quantum efficiency (ηex) of 84.3%. The second was a high-power white LED, fabricated from the above high-power blue LED, and had a high ϕe of 756 mW at 350 mA. ϕv and ηL of the high-power white LED were 203 lm and 183 lm W−1 at 350 mA, respectively. The third was a high-power white LED fabricated from four high-power blue LED dies. ϕv and ηL of the high-power white LED were 1913 lm and 135 lm W−1 at 1 A, respectively. The white LED had a higher flux than a 20 W-class fluorescent lamp and 1.5 times the luminous efficacy of a tri-phosphor fluorescent lamp (90 lm W−1).

Internal quantum efficiency enhancement of GaInN/GaN quantum-well structures using Ag nanoparticles

“…In order to improve GaInN-based LEDs both enhancement of the IQE and development of an efficient light extraction techniques to 'drag' the photons out of the LED crystal are required. 3,4 It is well known that spontaneous emission, including the recombination rate and the emission profile, can be modified by the nearby photonic environments. 5,6 The key concept underlying plasmon enhanced light emission is the local density of optical states (LDOS), which accounts for the available number of modes per frequency at a certain position.…”

Solid‐state lighting

“…Indeed, a blue pump with an 81.3 % power conversion efficiency was recently demonstrated [6], implying a potential efficacy of 245 lm/W for white light with good color rendering quality.…”

Efficiency enhancement of InGaN amber MQWs using nanopillar structures

“…InGaN MQW-based LEDs are capable of emitting in the full visible spectral range by adjusting the indium content. Extremely high external quantum efficiency (EQE) larger than 80% has already been achieved on blue LEDs [5]. Meanwhile, the EQE of longer-wavelength LEDs (green, yellow, red) is still relatively lower than for blue devices.…”