노광동 교수

Abstract Hybrid organic–inorganic perovskite semiconductors have shown potential to develop into a new generation of light‐emitting diode (LED) technology. Herein, an important design principle for perovskite LEDs is elucidated regarding optimal perovskite thickness. Adopting a thin perovskite layer in the range of 35–40 nm is shown to be critical for both device efficiency and stability improvements. Maximum external quantum efficiencies (EQEs) of 17.6% for Cs 0.2 FA 0.8 PbI 2.8 Br 0.2 , 14.3%

Perovskite semiconductors are actively investigated for high performance solar cells. Their large optical absorption coefficient and facile solution-based, low-temperature synthesis of thin films make perovskites also a candidate for light-emitting devices across the visible and near-infrared. Specific to their potential as optical gain medium for lasers, early work has demonstrated amplified spontaneous emission and lasing at attractively low thresholds of photoexcitation. Here, we take an impo

Abstract 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 −1 m −2 ). Here, Joule heating and inefficient thermal dissipation are shown to be major obstacles toward high radiance and long lifetime. Several thermal management strategies are proposed in this work, such as doping charge‐transport lay

Abstract Hybrid perovskite semiconductors represent a promising platform for color-tunable light emitting diodes (LEDs) and lasers; however, the behavior of these materials under the intense electrical excitation required for electrically-pumped lasing remains unexplored. Here, we investigate methylammonium lead iodide-based perovskite LEDs under short pulsed drive at current densities up to 620 A cm −2 . At low current density ( J < 10 A cm −2 ), we find that the external quantum efficiency

Abstract Near‐infrared (NIR) light‐emitting diodes (LEDs), with emission wavelengths between 800 and 950 nm, are useful for various applications, e.g., night‐vision devices, optical communication, and medical treatments. Yet, devices using thin film materials like organic semiconductors and lead based colloidal quantum dots face certain fundamental challenges that limit the improvement of external quantum efficiency (EQE), making the search of alternative NIR emitters important for the community

Abstract Electrically pumped lasing from hybrid organic–inorganic metal‐halide perovskite semiconductors could lead to nonepitaxial diode lasers that are tunable throughout the visible and near‐infrared spectrum; however, a viable laser diode architecture has not been demonstrated to date. Here, an important step toward this goal is achieved by demonstrating two distinct distributed feedback light‐emitting diode architectures that achieve low threshold, optically pumped lasing. Bottom‐ and top‐e

Abstract 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 dev

High-performance inorganic-organic lead halide perovskite solar cells (PSCs) are often fabricated with a liquid additive such as dimethyl sulfoxide (DMSO), which retards crystallization and reduces roughness and pinholes in the perovskite layers. However, DMSO can be trapped during perovskite film formation and induce voids and undesired reaction byproducts upon later processing steps. Here, it is shown that the amount of residual DMSO can be reduced in as-spin-coated films significantly through

Iodine-containing volatiles are major degradation products of halide perovskite materials under irradiation, yet iodine diffusion kinetics into and throughout organic hole transport materials (HTMs) and consequent reactions are largely unexplored. Here, we modify the Ca:O2 corrosion test to Ag:I2 to quantify I2 transmission rates through common organic HTMs. We observe I2 permeability to inversely correlate with HTM ionization energy, or the highest occupied molecular orbital (HOMO) energy. Trac

We demonstrate surface emitting distributed feedback (DFB) lasers across the red, green, and blue from densely packed colloidal quantum dot (CQD) films. The solid CQD films were deposited on periodic grating patterns to enable 2nd-order DFB lasing action at mere 120, 280, and 330 μJ/cm2 of optical pumping energy densities for red, green, and blue DFB lasers, respectively. The lasers operated in single mode operation with less than 1 nm of full-width-half-maximum. We measured far-field patterns s

Solution-processed organic–inorganic hybrid perovskites have recently emerged as promising low-cost materials for optoelectronic applications. However, exposure to light or applied bias causes phase separation of mixed-halide perovskites into iodide-rich domains, resulting in the shift of the bandgap energy toward the infrared for light-emitting devices. Proper selection of self-assembled and bulky organoammonium halide additives, 4-fluorobenzylammonium iodide bromide, FPMAI1–xBrx, to the mixed-

Colloidal quantum dots (CQD) are now making their entry to full-color displays, endowed by their brightness and single-material base. By contrast, many obstacles have been encountered in their use towards lasers. We demonstrate here optically pumped distributed feedback (DFB) lasers, based on close-packed, solid films self-assembled from type-I CQDs. Notably, the single mode CQD-DFB lasers could reach such a low threshold as to be pumpable with a compact pulsed source in a quasi-continuous wave

Metal halide perovskite semiconductors show considerable promise as an efficient coherent light source, but the extent of their spectral tunability and optical gain bandwidth have not been established. Here, we demonstrate continuously tunable single-mode lasing from halide perovskite thin films over a wide spectral range (758–804 nm for CH3NH3PbI3, 653–684 nm for Cs0.4(CH3NH3)0.6Pb(Br0.4I0.6)3, and 520–542 nm for CsPbBr3) at room temperature for the first time. The large optical gain bandwidth

Perovskite (CH3NH3PbI3) films possessing optical quality were prepared by solution-based spin-casting at room temperature. We report near infrared lasing with well-defined spatially coherent output from second-order surface-emitting distributed feedback grating structure with perovskite active media.