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By adopting the alkali metal sodium ion (Na+) doping strategy, the grain size of Cs 3 Bi 2 I 9 (CBI) thin film is significantly increased and the non-radiative recombination defects are effectively passivated. Therefore, the self-powered broadband detection performance of photoelectrochemical detector based on the high-quality CBIN x thin films is greatly enhanced. [Display omitted] • Defect passivated lead-free Cs 3 Bi 2 I 9 polycrystalline perovskite thin film was prepared by alkali metal sodium cation doping. • A simple self-powered broadband photoelectrochemical detector based on Cs 3 Bi 2 I 9 thin film was fabricated. • The detector exhibits excellent photodetection performance without bias at UV, visible and near-infrared region. All-inorganic lead-free bismuth-based perovskites have attracted great interest in the optoelectronic applications due to their low toxicity and excellent stability. However, the inherent polycrystalline (PC) of perovskite films suffers severe charge recombination due to the large numbers of trap density. Herein, high-quality Cs 3 Bi 2 I 9 (CBI) PC thin films are prepared by solution process with alkali sodium (Na+) cation doping strategy, resulting large grain size and lower trap density. Afterward, the photoelectrochemical-type detectors based on Na+ doped CBI thin film is constructed for the first time. The photodetector displays a broadband photoresponse covering ultraviolet (UV), visible and near-infrared (NIR) ranges. Significantly, by precisely controlling Na+ doping concentration, the performance of photodetector can be largely enhanced with the highest responsivity of 53.38 mA/W and detectivity of 5.99 × 109 Jones without bias, and these results exceed the performance of most reported CBI PC thin film based photodetectors. In addition, the photodetector exhibits an obvious increase in photoresponse and outstanding photo-stability after more than 150 on/off cycles. Finally, the mechanism of Na+ doping is further discussed. These results provide an outstanding example for the preparing high-quality CBI PC thin film and also demonstrate the great potential of CBI in the application of self-powered broadband photodetectors. [ABSTRACT FROM AUTHOR]

In this work, (Al x Ga 1-x) 2 O 3 thin films were grown on Al 2 O 3 (0001) substrate by radio frequency magnetron sputtering using Al/Ga 2 O 3 target. The analysis of crystalline structure, morphology, transmittance and bandgap after various annealing temperatures were investigated in detail. The films were oriented along ( 2 — 01) plane, and the crystalline quality improved with increasing annealing temperature. The stoichiometries of films can be regard as (Al 0.33 Ga 0.67) 2 O 3 according to X-ray photoelectron spectroscopy and the additional compressive stress in the sample which annealed at 900 °C was certified. The bandgap of annealed films was totally decreased due to increasing magnitude of compressive stress and grain size. Therefore, these results may suggest the way to tune the band gap of β-(Al x Ga 1-x) 2 O 3 films by varying the residual stress through annealing and indicate the optimum annealing temperature for (Al 0.33 Ga 0.67) 2 O 3 thin films is about 800 °C. • The (Al x Ga 1-x) 2 O 3 films were deposited using Al/Ga 2 O 3 target. • All the samples were monoclinic structure with the (−201) preferred orientation. • Post-annealing can improve the crystalline of (Al x Ga 1-x) 2 O 3 thin films. • The remigration of Al atoms took place after annealing at 900 °C. [ABSTRACT FROM AUTHOR]

In this work, Ga 2 O 3 thin films were grown on Al 2 O 3 (0001) substrate by radio frequency magnetron sputtering. The influence of sputtering power on crystalline structure, morphology, transmittance, band gap, and photoluminescence were investigated in detail. X-ray diffraction results showed that the β-Ga 2 O 3 films were oriented along ( 2 ¯ 01 ) plane, and the crystalline quality improved with increasing sputtering power. Scanning electron microscope images revealed that the proportion of large-size grain increased with increasing sputtering power. The β-Ga 2 O 3 films displayed very high transmittance close to 100% in visible region. Photoluminescence spectra showed that all the films exhibited intense blue and green emission centered at approximately 430 nm and 550 nm originated from the donor-acceptor pair recombination. [ABSTRACT FROM AUTHOR]

The (In x Ga 1-x) 2 O 3 thin films were deposited on sapphire substrates by radio frequency magnetron sputtering with increasing sputtering pressure from 0.6 Pa to 1.6 Pa. X-ray diffraction analysis indicated In composition of (In x Ga 1-x) 2 O 3 thin films maintained constant with the increase of sputtering pressure and In content and bandgaps of (In x Ga 1-x) 2 O 3 thin films were estimated to be 6% and 4.78 eV by Vegard's law, respectively. The influence of sputtering pressure on structural and optical properties was discussed in detail. Especially, the origin of different emission of (In x Ga 1-x) 2 O 3 thin films was investigated. The role of V Ga defects on the green emission centered at about 550 nm had been clarified. The energy band diagram of (In x Ga 1-x) 2 O 3 thin film was also proposed with intrinsic defect levels. • In content of (In x Ga 1-x) 2 O 3 films is 6% for all sputtering pressure condition. • Defects play an important role in luminescence. • Green luminescence is related to gallium vacancies. [ABSTRACT FROM AUTHOR]