Effect of Oxygen Plasma on β‑Ga₂O₃ Deep Ultraviolet Photodetectors Fabricated by Plasma-Assisted Pulsed Laser Deposition

We fabricated metal–semiconductor–metal-structured β-Ga2O3 photodetectors using a plasma-assisted pulsed laser deposition system with various oxygen plasma radio frequency (RF) powers ranging from 0 to 100 W. All optoelectronic properties of the material were enhanced as the RF power increased. β-Ga2O3 photodetector with RF power of 100 W showed the best optoelectronic characteristics, such as photoresponsivity of 0.39 A/W, external quantum efficiency of 192.61%, and detectivity of 9.09 × 1013 cm Hz1/2/W. In addition, photo-switching analysis revealed the fastest photoresponse speeds (1.46 and 0.21 s) for on/off switching. These results originate from the decrease in the oxygen vacancy defect concentration in the β-Ga2O3 films by the oxygen RF power. Our results suggest that β-Ga2O3 photodetectors fabricated with oxygen plasma can optimize and improve the photodetection performance and can be applied for future deep ultraviolet detectors

Improved Stability of MAPbI₃ Perovskite Solar Cells Using Two-Dimensional Transition-Metal Dichalcogenide Interlayers

Perovskite solar cells (PSCs) have been receiving considerable attention as next-generation solar cells. However, their short lifetime is a major obstacle to their commercialization. In addition to the properties of the materials used in PSCs, their interfaces play an important role in device stability by maintaining their initial design. In this study, we developed a transition-metal dichalcogenide (TMD) as a stable and efficient interlayer. MoS2 and WSe2 were applied to both the hole and electron transport sides of the PSCs with general FTO/TiO2/MAPbI3/Spiro-OMeTAD/Au structures, respectively. Owing to efficient charge transfer by TMD interlayers, our PSCs achieved a 19.24% efficiency, which is higher than the efficiency of the control devices (18.22%). Furthermore, the device stability was markedly improved by the passivation and strain-release effects of the TMD interlayers. Thus, the PSCs with TMD interlayers demonstrated a stable performance over 1000 h under damp heat (85 °C and 85% relative humidity) conditions

Highly Enhanced Photoresponsivity of a Monolayer WSe₂ Photodetector with Nitrogen-Doped Graphene Quantum Dots

Hybrid structures of two-dimensional (2D) materials and quantum dots (QDs) are particularly interesting in the field of nanoscale optoelectronic devices because QDs are efficient light absorbers and can inject photocarriers into thin layers of 2D transition-metal dichalcogenides, which have high carrier mobility. In this study, we present a heterostructure that consists of a monolayer of tungsten diselenide (ML WSe₂) covered by nitrogen-doped graphene QDs (N-GQDs). The improved photoluminescence of ML WSe₂ is attributed to the dominant neutral exciton emission caused by the n-doping effect. Owing to strong light absorption and charge transfer from N-GQDs to ML WSe₂, N-GQD-covered ML WSe₂ showed up to 480% higher photoresponsivity than that of a pristine ML WSe₂ photodetector. The hybrid photodetector exhibits good environmental stability, with 46% performance retention after 30 days under ambient conditions. The photogating effect also plays a key role in the improvement of hybrid photodetector performance. On applying the back-gate voltage modulation, the hybrid photodetector shows a responsivity of 2578 A W^–1, which is much higher than that of the ML WSe₂-based device

Compliance-Free Multileveled Resistive Switching in a Transparent 2D Perovskite for Neuromorphic Computing

We demonstrate the pulsed voltage tunable multileveled resistive switching (RS) across a promising transparent energy material of (C₄H₉NH₃)₂PbBr₄. The X-ray diffraction and scanning electron microscopy results confirm the growth of (001) plane-orientated nanostructures of (C₄H₉NH₃)₂PbBr₄ with an average size of ∼360 nm. The device depicts optical transmittance higher than 70% in the visible region and efficient absorbance in the ultraviolet region. The current–voltage measurement shows the bipolar RS. In addition, depending on the magnitude of applied electric pulse, the current across the device can be flipped in four different levels, which remain stable for long time, indicating multimode RS. Further, the current across the device increases gradually by applying continuous pulses, similar to the biological synapses. The observed results are attributed to the electric field-induced ionic migration across the (C₄H₉NH₃)₂PbBr₄. The existing study should open a new avenue to apply this promising energy material of perovskite for multifunctional advanced devices