Nitrides Seminar - Vincent Rienzi

Nitrides Seminar

Tuesday, May 13, 2025, 12:00PM

Attend in person at ESB 1001!

Zoom option also available

Vincent Rienzi

Graduate Student Researcher, Nakamura Group

University of California, Santa Barbara

Efficient and Spectrally Stable c-plane Red III-Nitride Light Emitting Diodes

In 2020, lighting accounted for 14% of total U.S. electricity usage, and of that 14% light emitting diodes accounted for 31%. Much of the ubiquitous integration of LEDs into many aspects of modern society is attributed to the development of GaN and its III-N alloys. Color stability is a major challenge in long wavelength III-N LEDs. As current density increases, a monotonic decrease in peak wavelength is observed and the LED blueshifts. In this work, we demonstrate high external quantum efficiency (EQE) red LEDs with negligible blueshift and improved spectral, and therefore color, stability from 0.01 A/cm² to 150 A/cm². 

The 1st generation of these efficient and improved color stability LEDs had a total cumulative peak wavelength blueshift of only 7 nm, substantially lower than what is reported elsewhere in red III-N LED literature, while achieving a peak EQE and wall-plug efficiency (WPE) of 7.5% and 4.8%, respectively. The 2nd generation of these LEDs are 50% more efficient while still demonstrating improved color stability and redshifting. Furthermore, these LEDs are their most efficient when they are at their longest dominant wavelength, which is when an LED is its most optically red, and has never been observed before in III-N LEDs due to the ubiquitous monotonic blueshifting. This work opens up the possibility to design explicitly for LEDs to be their most efficient at the desired color and brightness of their application. Future work will focus on incorporating V-Defects into the LEDs to further improve WPE while maintaining this color stability. Additionally, performing more fundamental experiments to better understand the physical mechanism(s) behind this improved color stability behavior is a high priority. This work is supported by the Solid State Lighting and Energy Electronics Center (SSLEEC), the Korean Institute for Advancement of Technology (KIAT), and Department of Energy Award # DE-EE0009691.

HOST: Dr. Yifan Yao