Size-dependent performance of white light μLEDs for intelligent vehicle lighting and communication

In this paper, size-dependent illumination performances of white light micro light-emitting diodes (μLEDs) and a visible light communication (VLC) system were demonstrated. The white light μLEDs from 10 μm to 200 μm were prepared by exciting three phosphors with blue μLEDs and the current density versus voltage, luminous efficiency, and electroluminescence (EL) spectra were measured. At 300 A/cm², the luminous efficiency of the 60 μm white μLED was 1.6 times greater than that of the 200 μm white LED, and we found that the smaller chips are more advantageous in luminous efficacy at higher current densities. The trend of the CIE chromaticity diagram versus the current density for the 200 μm, 60 μm, and 10 μm white light LED were analyzed, revealing that the smaller white light μLED had the advantage of reducing the shift of the coordinate in CIE 1931. Further, we investigated the communication characteristic of white μLEDs and found that the -3 dB modulation bandwidth of the 60 μm white light μLED was 151.57 MHz at 2000 A/cm² and a data rate up to 1.741 Gbps could be attained when it was used in a VLC system at a free space transmission distance of 0.25 m by combining orthogonal frequency division multiplexing (OFDM) modulation without optical filters or equalization circuits. Our work is significant in accelerating the applications of white light μLEDs for intelligent vehicle lighting and communication.