Ultralow-voltage operation of light-emitting diodes

TL;DR

This study reveals that various LEDs can emit light at voltages significantly below their bandgaps, challenging traditional assumptions and enabling ultra-low-voltage optoelectronic applications.

Contribution

The paper demonstrates universal ultralow-voltage electroluminescence across multiple LED types and showcases a perovskite LED transmitting data at 1V, below silicon's bandgap.

Findings

LEDs emit at 36%-60% of their bandgap voltages.

Universal behavior observed across different LED classes.

Perovskite LEDs can transmit data at 1V.

Abstract

The radiative recombination of injected charge carriers gives rise to electroluminescence (EL), a central process for light-emitting diode (LED) operation. It is often presumed in some emerging fields of optoelectronics, including perovskite and organic LEDs, that the minimum voltage required for light emission is the semiconductor bandgap divided by the elementary charge. Here we show for many classes of LEDs, including those based on metal halide perovskite, organic, chalcogenide quantum-dot and commercial III-V semiconductors, photon emission can be generally observed at record-low driving voltages of 36%-60% of their bandgaps, corresponding to a large apparent energy gain of 0.6-1.4 eV per emitted photon. Importantly, for various classes of LEDs with very different modes of charge injection and recombination (dark saturation current densities ranging from ~10^-35 to ~10^-21 mA/cm2), their EL intensity-voltage curves under low voltages exhibit similar behaviors, revealing a universal origin of ultralow-voltage device operation. Finally, we demonstrate as a proof-of-concept that perovskite LEDs can transmit data efficiently to a silicon detector at 1V, a voltage below the silicon bandgap. Our work provides a fresh insight into the operational limits of electroluminescent diodes, highlighting the significant potential of integrating low-voltage LEDs with silicon electronics for next-generation communications and computational applications.