2022 New's Items

Low voltage AC electroluminescence in silicon MOS capacitors

Rahman IKMR
Uddin SZ
Kim H
Higashitarumizu N
Javey A
2022

Low power silicon based light source and detector are attractive for on-chip photonic circuits given their ease of process integration. However, conventional silicon light emitting diodes emit photons with energies near the band edge where the corresponding silicon photodetectors lack responsivity. On the other hand, previously reported hot carrier electroluminescent silicon devices utilizing a reverse biased diode require high operating voltages. Here, we investigate hot carrier electroluminescence in silicon metal–oxide–semiconductor capacitors operating under transient voltage...

Efficiency Roll-Off Free Electroluminescence from Monolayer WSe2

Uddin SZ
Higashitarumizu N
Kim H
Rahman IKMR
Javey A
2022

Exciton–exciton annihilation (EEA) is a nonradiative process commonly observed in excitonic materials at high exciton densities. Like Auger recombination, EEA degrades luminescence efficiency at high exciton densities and causes efficiency roll-off in light-emitting devices. Near-unity photoluminescence quantum yield has been demonstrated in transition metal dichalcogenides (TMDCs) at all exciton densities with optimal band structure modification mediated by strain. Although the recombination pathways in TMDCs are well understood, the practical application of light-emitting devices...

Enhanced Neutral Exciton Diffusion in Monolayer WS2 by Exciton–Exciton Annihilation

Uddin SZ
Higashitarumizu N
Kim H
Yi J
Zhang X
Chrzan DC
Javey A
2022

Dominant recombination pathways in monolayer transition metal dichalcogenides (TMDCs) depend primarily on background carrier concentration, generation rate, and applied strain. Charged excitons formed in the presence of background carriers mainly recombine nonradiatively. Neutral excitons recombine completely radiatively at low generation rates, but experience nonradiative exciton–exciton annihilation (EEA) at high generation rates. Strain can suppress EEA, resulting in near-unity photoluminescence quantum yield (PL QY) at all exciton densities. Although exciton diffusion is the...

Resettable Microfluidics for Broad-Range and Prolonged Sweat Rate Sensing

Bariya M
Davis N
Gillan L
Jansson E
Kokkonen A
McCaffrey C
Hiltunen J
Javey A
2022

Wearable sweat sensors are emerging as promising platforms for personalized and real-time tracking of evolving health and fitness parameters. While most wearable sweat sensors focus on tracking biomarker concentration profiles, sweat secretion rate is a key metric with broad implications for assessing hydration, cardiac, and neural conditions. Here we present a wearable microfluidic sensor for continuous sweat rate measurement. A discrete impedimetric sensing scheme relying on interdigitated electrodes within a microfluidic sweat collector allows for precise and selective sweat rate...

Orientated Growth of Ultrathin Tellurium by van der Waals Epitaxy

Zhao C
Batiz H
Yasar B
Ji W
Scott MC
Chrzan DC
Javey A
2022

Tellurium, as an elemental van der Waals semiconductor, has intriguing anisotropic physical properties owing to its inherent 1D crystal structure. To exploit the anisotropic and thickness-dependent behavior, it is important to realize orientated growth of ultrathin tellurium. Here, van der Waals epitaxial growth of Te on the surface of 2D transition metal dichalcogenides is systematically investigated. Orientated growth of Te with a thickness down to 5 nm is realized on three-fold symmetric substrates (WSe2, WS2, MoSe2...

Bright Mid-Wave Infrared Resonant-Cavity Light-Emitting Diodes Based on Black Phosphorus

Gupta N
Kim H
Azar NS
Uddin SZ
Lien DH
Crozier KB
Javey A
2022

The mid-wave infrared (MWIR) wavelength range plays a central role in a variety of applications, including optical gas sensing, industrial process control, spectroscopy, and infrared (IR) countermeasures. Among the MWIR light sources, light-emitting diodes (LEDs) have the advantages of simple design, room-temperature operation, and low cost. Owing to the low Auger recombination at high carrier densities and direct bandgap of black phosphorus (bP), it can serve as a high quantum efficiency emitting layer in LEDs. In this work, we demonstrate bP-LEDs exhibiting high external quantum...

Engineering Exciton Recombination Pathways in Bilayer WSe2 for Bright Luminescence

Uddin SZ
Higashitarumizu N
Kim H
Rabani E
Javey A
2022

Exciton–exciton annihilation (EEA) in counterdoped monolayer transition metal dichalcogenides (TMDCs) can be suppressed by favorably changing the band structure with strain. The photoluminescence (PL) quantum yield (QY) monotonically approaches unity with strain at all generation rates. In contrast, here in bilayers (2L) of tungsten diselenide (WSe2) we observe a nonmonotonic change in EEA rate at high generation rates accompanied by a drastic enhancement in their PL QY at low generation rates. EEA is suppressed at both 0% and 1% strain, but activated at...

Zwitterions in 3D Perovskites: Organosulfide-Halide Perovskites

Li J
Chen Z
Ginsberg NS
Chapman KW
Filip MR
Karunadasa HI
2022

Although sulfide perovskites usually require high-temperature syntheses, we demonstrate that organosulfides can be used in the milder syntheses of halide perovskites. The zwitterionic organosulfide, cysteamine (CYS; +NH3(CH2)2S–), serves as both the X– site and A+ site in the ABX3 halide perovskites, yielding the first examples of 3D organosulfide-halide perovskites: (CYS)PbX...

Static Disorder has Dynamic Impact on Energy Transport in Biomimetic Light-Harvesting Complexes

Hamerlynck LM
Bischoff AJ.......
Francis MB
Ginsberg NS
2022

Despite extensive studies, many questions remain about what structural and energetic factors give rise to the remarkable energy transport efficiency of photosynthetic light-harvesting protein complexes, owing largely to the inability to synthetically control such factors in these natural systems. Herein, we demonstrate energy transfer within a biomimetic light-harvesting complex consisting of identical chromophores attached in a circular array to a protein scaffold derived from the tobacco mosaic virus coat protein. We confirm the capability of energy transport by observing ultrafast...

Busting through quantum dot barriers

Ginsberg NS
Tisdale WA
2022

Early time transient absorption microscopy in quantum dot solids reveals anomalous exciton transport with multiple different temporal regimes within hundreds of femtoseconds after photoexcitation.