Ali Javey (Advisor)

Research Advised by Professor Ali Javey

Javey Group:  List of Projects | List of Researchers

BPN982: Color-Tunable Alternating Current Light Emitting Diodes

Jongchan Kim
Vivian Wang
2022

Alternating current (AC) driven light emitting devices (LEDs) are recently dragging attention due to its efficient color tunability. These devices consist of multilayer structure as the direct current (DC) driven LEDs, but the multilayer structure has drawbacks such as the large amount of material usage that increases the fabrication cost, and the difficult yield control due to a number of processing steps. In contrast, a recently demonstrated AC driven LED with a single contact has several advantages compared to the previous structures such as simple device structure, diverse...

Single-Pixel Reconstructive Mid-Infrared Micro-Spectrometer

Kaichen Dong
Jiachen Li
Tiancheng Zhang
Fangda Gu
Yuhang Cai
Niharika Gupta
Ali Javey
Jie Yao
Junqiao Wu
2023

Miniaturized spectrometers in the mid-infrared (MIR) are critical in developing next-generation portable electronics for advanced sensing and analysis. The bulky gratings or detector/filter arrays in conventional micro-spectrometers set a physical limitation to their miniaturization. In this work, we demonstrate a single-pixel MIR micro-spectrometer that reconstructs the sample transmission spectrum by a spectrally dispersed light source instead of spatially grated light beams. The spectrally tunable MIR light source is realized based on the thermal emissivity engineered via the metal-...

Anomalous Thickness Dependence of Photoluminescence Quantum Yield in Black Phosphorous

Naoki Higashitarumizu
Shiekh Zia Uddin
Daniel Weinberg
Nima Sefidmooye Azar
I K M Reaz Rahman
Vivian Wang
Kenneth B. Crozier
Eran Rabani
Ali Javey
2023

Black phosphorus has emerged as a unique optoelectronic material, exhibiting tunable and high device performance from mid-infrared to visible wavelengths. Understanding the photophysics of this system is of interest to further advance device technologies based on it. Here we report the thickness dependence of the photoluminescence quantum yield at room temperature in black phosphorus while measuring the various radiative and non-radiative recombination rates. As the thickness decreases from bulk to ~4 nm, a drop in the photoluminescence quantum yield is initially observed due to enhanced...

Flexible Vanadium Dioxide Photodetectors for Visible to Longwave Infrared Detection at Room Temperature

Sivacarendran Balendhran
Mohammad Taha
Shifan Wang
Wei Yan
Naoki Higashitarumizu
Dingchen Wen
Nima Sefidmooye Azar
James Bullock
Paul Mulvaney
Ali Javey
2023

Flexible optoelectronics is a rapidly growing field, with a wide range of potential applications. From wearable sensors to bendable solar cells, curved displays, and curved focal plane arrays, the possibilities are endless. The criticality of flexible photodetectors for many of these applications is acknowledged, however, devices that are demonstrated thus far are limited in their spectral range. In this study, flexible photodetectors are demonstrated using a VOx nanoparticle ink, with an extremely broad operating wavelength range of 0.4 to 20 µm. This ink is synthesized using a simple and...

Javey Lab: Berkeley Engineers Develop Multicolored Light-Emitting Array on a Single Chip

May 10, 2023

An array of light-emitting devices with 49 different, individually addressable colors.

An array of light-emitting devices with 49 different, individually addressable colors. (Image by Vivian Wang) With limitless colors, the device may lead to advances in spectroscopy May 10, 2023 by Marni Ellery

Multicolored light-...

Shogo Tajima

Visiting Industry Fellow
Azbil Corp
Professor Ali Javey (Advisor)

Wenbo Ji

Former Graduate Student Researcher
Materials Science & Engineering
Professor Ali Javey (Advisor)
Ph.D. 2022 (Anticipated)

Enhanced Neutral Exciton Diffusion in Monolayer WS 2 by Exciton–Exciton Annihilation

Shiekh Zia Uddin
Naoki Higashitarumizu
Hyungjin Kim
Jun Yi
Xiang Zhang
Daryl Chrzan
Ali Javey
2022
2 ABSTRACT: 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...

Efficiency Roll-Off Free Electroluminescence from Monolayer WSe2

Shiekh Zia Uddin
Naoki Higashitarumizu
Hyungjin Kim
I K M Reaz Rahman
Ali Javey
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 has...