Intense Electrical Pulsing of Perovskite Light Emitting Diodes under Cryogenic Conditions

Abstract

As the threshold for stimulated emission is significantly reduced at cryogenic temperatures, cooling of perovskite light emitting diodes (PeLEDs) is considered an essential strategy for reaching injection lasing in perovskite diodes. In this work, we demonstrate the intense electrical pulsing of a PeLED stack up to a few kA cm−2 at cryogenic conditions. A high external quantum efficiency (EQE) of 2.9% at 1 kA cm−2 and a radiance >1.95 × 105 W Sr−1 m−2 are achieved when exciting the device with 250 ns electrical pulses at 77 K, showing three times enhancement in comparison with room temperature operation. Furthermore, we provide a comprehensive understanding on how the ion distribution can affect the PeLED characteristics and show that ion motions can be manipulated at cryogenic conditions. This opens new routes for novel material and device designs for further improving PeLED performance.

Toward Nonepitaxial Laser Diodes

“…Similar strategies have been used in several other studies, and PeLEDs with operating current densities up to 2.5 kA/cm 2 have been reported. ,, In addition to reducing the device active area, additional thermal management strategies, such as the use of more thermally conductive substrates (e.g., sapphire substrates), the addition of heat sinks, and the use of more electrically conductive charge-transport layers (e.g., by electrical doping) are beneficial for improving EQE at high current densities, with an EQE of 1% achieved at 1 kA/cm 2 in Figure c . Elkhouly et al subsequently reported PeLEDs operating at 77 K with an EQE of 2.9% at 1 kA/cm 2 driven by 250 ns electrical pulses (Figure d), which is significant since the threshold of most perovskite lasers is strongly reduced at a low temperature.…”

“…25,300,301 In addition to reducing the device active area, additional thermal management strategies, such as the use of more thermally conductive substrates (e.g., sapphire substrates), the addition of heat sinks, and the use of more electrically conductive charge-transport layers (e.g., by electrical doping) are beneficial for improving EQE at high current densities, with an EQE of 1% achieved at 1 kA/cm 2 in Figure 26c. 25 Elkhouly et al 302 subsequently reported PeLEDs operating at 77 K with an EQE of 2.9% at 1 kA/cm 2 driven by 250 ns electrical pulses (Figure 26d), which is significant since the threshold of most perovskite lasers is strongly reduced at a low temperature. One limitation of using an insulating SiO 2 layer to reduce PeLED active area is the large parasitic capacitance of this device structure and its associated RC time constant, which limits the pulse rise time (the typical EL rise time for such devices is on the order of several hundred nanoseconds).…”

Scattered Emission Profile Technique for Accurate and Fast Assessment of Optical Gain in Thin Film Lasing Materials

“…Thin-film materials such as metal halide perovskites and colloidal quantum dots have garnered a lot of research interest as active media for lasers. − Over the past decades there have been numerous demonstrations of optically pumped lasing from these materials. − Simultaneously, there have also been several developments toward pushing high current densities into light-emitting diodes (LEDs), with the goal of achieving injection lasing. − Indeed, such thin-film injection lasers, when achieved, would eliminate a number of shortcomings of today’s heterointegrated lasers on chips, by enabling cost-effective processing, ease of manufacturing, and lattice-independent substrate compatibility. They can also allow to envisage new concepts, such as flexible lasers. , …”

Enhancement of Amplified Spontaneous Emission by Electric Field in CsPbBr3 Perovskites

“…Our data suggests that sweeping the mobile ions out from the bulk of the film significantly increases the radiative efficiency and optical gain. In terms of electrical pumping, intense current driven LEDs − adopt brief electrical pulses (ns to μs length), which are too short to redistribute the mobile ions. Therefore, driving such LEDs under simultaneous DC and pulsed electrical excitation may be helpful for realizing the electrical injection lasing .…”

“…Halide perovskite semiconductors are an emerging class of laser gain media − due to their high absorption coefficient, emission color tunability, and low-cost solution processability. Following the milestone of room-temperature continuous-wave (CW) lasing, several efforts − on intense electrical driving of light-emitting diodes (LEDs) have been made. One of the most exciting results is an external quantum yield of 1% at 10 kA cm –2 achieved under nanosecond electrical pulses .…”