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Improving the open‐circuit voltage (VOC) is a fundamental target for photovoltaic devices to obtain high photoelectric conversion efficiency (PCE). Here, it is reported that the chemical doping of graphene hole transport layer has a significant impact on the VOC of solar‐blind ultraviolet (SBUV) photovoltaic detectors. It has been demonstrated that the external quantum efficiency (EQE) of graphene/AlGaN/SiC heterojunction photovoltaic detectors increases from 21.6% to 38.1% when the Fermi level of graphene is precisely pulled down by a simple charge transfer process. Without sacrificing response speed, the ≈75% increase in EQE together with responsivity is the result of the enhancement of VOC from 1.10 to 2.02 V. This work sheds light on the correlation between VOC and graphene Fermi level in SBUV detectors, and provides effective avenues to modulate the PCE of photovoltaics. [ABSTRACT FROM AUTHOR]

Recently, 1D van der Waals materials with appealing optoelectronic properties different from 2D layered materials have attracted widespread attention. However, the existing methods are incapable of growing the high‐quality and large‐size 1D van der Waals materials to a certain extent. Here, a new method of organic liquid phase synthesis followed by annealing is proposed, which overcomes the crystal size limitation caused by chemical vapor deposition and successfully synthesizes the high‐quality ultra‐long (millimeter level) van der Waals CdBr2 micro/nanobelts without being limited by substrate matching. The Raman tensor of CdBr2 with extremely high anisotropy is extracted, revealing the structure and physical properties of this van der Waals crystal. What is more, based on this material, the photodetectors with high responsivity are manufactured. Methodologically, compared with current methods, this work indicates the advantages of liquid phase synthesis in growing high‐quality, large‐size 1D van der Waals materials. It is believed that the method proposed in this paper can provide a noble perspective for the study of 1D van der Waals materials and arouse a lot of interest in the field of optoelectronics. [ABSTRACT FROM AUTHOR]

An urgent demand for electronic and optoelectronic devices able to work in extreme environments promotes a series of research studies on semiconductor materials. Cubic boron phosphide (BP) as a semiconductor material with excellent characteristics shows great application potential. However, since the synthesis conditions required are difficult to achieve and the growth mechanism of BP is still unclear, there are few reports on the basic properties of BP and pure isotope BP, resulting in a narrow understanding of their special physical properties. Here, we successfully obtained highly pure isotopic 10 BP crystals by a vapor-liquid-solid (VLS) method unconventionally designed, which successfully overcomes the thermodynamic conflict between the high melting point of the boron element and low sublimation temperature of the phosphorus element. The 10 BP achieved owns an aspect ratio as high as 10 4 and a hardness up to 41 GPa. Besides, as an indirect bandgap semiconductor, it has ultrawide red emission spectra, a p-type conductivity with extremely low resistivity, and excellent photoelectronic and piezoelectric characteristics. Furthermore, compared with other superhard semiconductors like cubic BN and diamond, 10 BP has an obvious advantage of lower growth temperature (1200 °C). All these characteristics confirm the prospects owned by 10 BP in its applications to the field of high-conductivity, optoelectronic, strain-sensing, and superhard semiconductors.

(Al x Ga 1- x ) 2 O 3 is emerging as a promising wide-band-gap sesquioxide for vacuum-ultraviolet (VUV, 10-200 nm) photodetectors and high-power field-effect transistors. However, how the key parameters such as the band gap and crystalline phase of the (Al x Ga 1- x ) 2 O 3 -based device vary with stoichiometry has not been explicitly defined, which is due to the unclear underlying mechanism of the Al local coordination environment. In this work, a high-pressure O 2 (20 atm) annealing (HPOA) strategy that can significantly improve the crystallinity of β-(Al x Ga 1- x ) 2 O 3 and achieve a tunable optical band gap was proposed, facilitating the revelation of the local structure of Al 3+ varying with Al content and the kinetic mechanism of Al 3+ diffusion. By combining the as-HPOA-treated single-crystalline β-(Al 0.69 Ga 0.31 ) 2 O 3 films with p-type graphene (p-Gr), which serves as a transparent conductor, a VUV photovoltaic detector is fabricated, showing an improved photovoltage (0.80 V) and fast temporal response (2.1 μs). All of these findings provide a rewarding and important strategy for enhancing the band-gap tunability of sesquioxides, as well as the flexibility of zero-power-consumption photodetectors.