The performance of lead-halide perovskite light-emitting diodes (LEDs) has increased rapidly in recent years. However, most reports feature devices operated at relatively small current densities (<500 mA/cm 2 ) with moderate radiance (<400 W/sr•m 2 ). Here, Joule heating and inefficient thermal dissipation are shown to be major obstacles towards high radiance and long lifetime. Several thermal management strategies are proposed in this work, such as doping charge-transport layers, optimizing

be grown epitaxially on specific substrates, silicon not being one of them.Metal halide perovskite light-emitting diodes (PeLEDs) hold the potential for a new generation of display and lighting technology, [1][2][3][4][5][6][7] featuring high color quality, energy efficiency, and low manufacturing cost. Furthermore, perovskites can be deposited from solutions/inks, which means that they can be deposited on virtually any substrate including silicon. Perovskite LEDs have been shown to be promising for optical communications. [8] However, the operation speed of PeLEDs is still relatively slow, with electroluminescence (EL) rise times of several hundred nanoseconds or longer. [9][10][11][12] The slow operation speed and response time of PeLEDs limit their potential for a wider scope of applications, such as interchip and intrachip optical communications, currently realized with more expensive technologies using III-V semiconductors.Reducing the EL rise time of PeLEDs will not only increase their potential utility for applications in optical communications, but also contribute to the development of an electrically driven perovskite laser diode, which would be transformative in the optoelectronics realm as a low-cost laser source compatible with silicon microelectronics. Despite significant progress toward this goal, [13][14][15][16] electrically driven lasing in perovskites has not yet been achieved. One challenge is that the current density reported to date does not exceed the estimated threshold required for lasing. Reducing the EL rise time would enable shorter pulse operation, making it possible for PeLEDs to operate at higher current densities due to reduced Joule heating. [10,17] Furthermore, high-speed pulsed operation of PeLEDs will allow us to probe electrically stimulated chargecarrier dynamics and reveal mechanisms that prevent PeLEDs from operating efficiently or lasing under electrical excitation. This understanding is particularly important as optically pumped lasing death has been observed for perovskite thin films within 25 ns, [18] and optical and electrical excitations are considerably distinct.Both extrinsic factors (e.g., parasitic capacitance and resistance) and intrinsic factors (e.g., long recombination lifetime of charge carriers in the light-generating process) can limit the speed of PeLEDs. However, the speed of PeLEDs reported so far appears to have been dominantly constrained by extrinsic factors, [8][9][10][11][12] excluding the possibility to probe more intrinsic While metal-halide perovskite light-emitting diodes (PeLEDs) hold the potential for a new generation of display and lighting technology, their slow operation speed and response time limit their application scope. Here, high-speed PeLEDs driven by nanosecond electrical pulses with a rise time of 1.2 ns are reported with a maximum radiance of approximately 480 kW sr −1 m −2 at 8.3 kA cm −2 , and an external quantum efficiency (EQE) of 1% at approximately 10 kA cm −2 , through improved device configuration designs and material consi...

While the performance of metal halide perovskite light-emitting diodes (PeLEDs) has rapidly improved in recent years, their stability remains a bottleneck to commercial realization. Here, we show that the thermal stability of polymer hole-transport layers (HTLs) used in PeLEDs represents an important factor influencing the external quantum efficiency (EQE) roll-off and device lifetime. We demonstrate a reduced EQE roll-off, a higher breakdown current density of approximately 6 A cm–2, a maximum radiance of 760 W sr–1 m–2, and a longer device lifetime for PeLEDs using polymer HTLs with high glass-transition temperatures. Furthermore, for devices driven by nanosecond electrical pulses, a record high radiance of 1.23 MW sr–1 m–2 and an EQE of approximately 1.92% at 14.6 kA cm–2 are achieved. Thermally stable polymer HTLs enable stable operation of PeLEDs that can sustain more than 11.7 million electrical pulses at 1 kA cm–2 before device failure.

Ideal ring resonators are characterized by travelling-wave counter-propagating modes, but in practice travelling waves can only be realized under unidirectional operation, which has proved elusive. Here, we have designed and fabricated a monolithic quantum cascade ring laser coupled to an active waveguide that allows for robust, deterministic and controllable unidirectional operation. Spontaneous emission injection through the active waveguide enables dynamical switching between the clockwise and counterclockwise states of the ring laser with as little as 1.6% modulation of the electrical input. We show that this behavior stems from a perturbation in the bistable dynamics of the ring laser. In addition to switching and bistability, our novel coupler design for quantum cascade ring lasers offers an efficient mechanism for outcoupling and light detection.

We demonstrate a novel method of inducing a gradual change in semiconductor conductivity by combining grayscale processing of photoresist and proton implantation. This method is flexible and lends itself to many applications in semiconductor-based optical and electrical devices.