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For low temperature (≤180 °C) processed perovskite solar cells (PSCs), SnO2 has been proven to be one of the most effective electron transporting layer. However, problems, such as poor electric conductivity and high defect density, inevitably exist in the SnO2 films which are fabricated using low temperature solution methods. Element doping of SnO2 film is a feasible strategy to alleviate the above problems. Herein, W doping of the SnO2 is realized through addition of ammonium tungstate hydrate into the molecular precursor of SnO2. The W doped SnO2 film exhibits higher conductivity, and can better extract and transport the electrons from the perovskite films. Hence, power conversion efficiency is boosted from 20.60 % for the reference PSCs to 21.83 % for PSCs fabricated on 2.5 mg mL−1 ammonium tungstate hydrate doped SnO2 films. [ABSTRACT FROM AUTHOR]

An efficient ferroelectric-enhanced side-gated single CdS nanowire (NW) ultraviolet (UV) photodetector at room temperature is demonstrated. With the ultrahigh electrostatic field from polarization of ferroelectric polymer, the depletion of the intrinsic carriers in the CdS NW channel is achieved, which significantly reduces the dark current and increases the sensitivity of the UV photodetector even after the gate voltage is removed. Meanwhile, the low frequency noise current power of the device reaches as low as 4.6 × 10−28 A2 at a source-drain voltage Vds = 1 V. The single CdS NW UV photodetector exhibits high photoconductive gain of 8.6 × 105, responsivity of 2.6 × 105 A W−1, and specific detectivity ( D*) of 2.3 × 1016 Jones at a low power density of 0.01 mW cm−2 for λ = 375 nm. In addition, the spatially resolved scanning photocurrent mapping across the device shows strong photocurrent signals near the metal contacts. This is promising for the design of a controllable, high-performance, and low power consumption ultraviolet photodetector. [ABSTRACT FROM AUTHOR]

Solution processed perovskite films usually exhibit numerous defect states on the surfaces of the films. Here in this work, oxalic acid (H2C2O4), which has two C=O groups, is selected and used to passivate the surface defects of the two‐step deposited perovskite films via post‐treatment. Strong interaction between H2C2O4 molecule and the Pb2+ ions located on the surface of perovskite film has been confirmed via Fourier transform infrared spectroscopy and X‐ray photoelectron spectroscopy, which can result in an effective suppress of the surface defects. Furthermore, time‐resolved PL spectrum indicates that carrier lifetime is prolonged in the H2C2O4 passivated perovskite film. After optimizing the H2C2O4 concentration, the target perovskite solar cells can demonstrate superior power conversion efficiencies (21.67 % from reverse measurement and 21.54 % from forward measurement) and superior device‐stability. [ABSTRACT FROM AUTHOR]

Hydrogel nanophotonic devices exhibit attractive tunable capabilities in structural coloration and optical display. However, current hydrogel‐based tunable strategies are mostly based on a single physical mechanism, and it remains a challenge to merge multiple mechanisms for active devices with integrated functionalities. Here, a hydrogel metagrating combining Fabry‐Pérot (FP) resonance and diffraction effects is proposed for achieving tunable absorption and dynamic wavelength‐selective beam steering. Through exploiting hydrogel shrinkage under electron‐beam exposure, a hydrogel nanocavity composed of Ag/Hydrogel/Ag three‐layer films can be directly printed with arbitrary patterns, enabling the direct‐pattering technique of metagrating. The hydrogel nanocavity performs as an FP‐type absorber, and its absorption peak rapidly shifts with humidity variation due to the hydrogel layer scaling. The response speed is <320 ms, and the absorption peak shift range is >150 nm. It is further demonstrated that the hydrogel metagrating exclusively deflects light at the resonance wavelength, and its operating wavelength can be actively switched by regulating ambient humidity. The proposed tunable hydrogel metagrating can promote new technologies of tunable metasurfaces for optical filtering, gas sensing, and optical imaging. [ABSTRACT FROM AUTHOR]

Low-dimensional tin selenide nanoribbons (SnSe NRs) show a wide range of applications in optoelectronics fields such as optical switches, photodetectors, and photovoltaic devices due to the suitable band gap, strong light–matter interaction, and high carrier mobility. However, it is still challenging to grow high-quality SnSe NRs for high-performance photodetectors so far. In this work, we successfully synthesized high-quality p-type SnSe NRs by chemical vapor deposition and then fabricated near-infrared photodetectors. The SnSe NR photodetectors show a high responsivity of 376.71 A W−1, external quantum efficiency of 5.65 × 104%, and detectivity of 8.66 × 1011 Jones. In addition, the devices show a fast response time with rise and fall time of up to 43 μ s and 57 μ s, respectively. Furthermore, the spatially resolved scanning photocurrent mapping shows very strong photocurrent at the metal-semiconductor contact regions, as well as fast generation-recombination photocurrent signals. This work demonstrated that p-type SnSe NRs are promising material candidates for broad-spectrum and fast-response optoelectronic devices. [ABSTRACT FROM AUTHOR]

A semiconductor oxide composite consisting of ZnO nanorods (NRs) and ZnO inverse opal (IO) was fabricated and used in the photoanode of quantum dot-sensitized solar cells (QDSSCs). Using polystyrene spheres 500, 800, 1000, and 1500 nm in diameter as the IO template, ZnO composites and corresponding QDSSCs with ZnO IOs of different pore sizes were fabricated. The oxide composite prepared with ZnO IOs of different pore sizes showed similar micro-morphologies; however, the photovoltaic performance of the QDSSCs based on these composites varied greatly. The QDSSCs based on the ZnO composite achieved high power conversion efficiencies (PCEs) of more than 6%, and the maximum PCE was 7.26% when the ZnO IO pore diameter in the composite was 800 nm. This resulted in very high PCE values for the QDSSCs using CdS/CdSe quantum dot sensitizers. With further interface modifications of NH4F and ZnS, the QDSSC achieved an even higher PCE value of 11.38%. Subsequently, the effects of ZnO IO pore size in the composite on QDSSC performance were investigated. [ABSTRACT FROM AUTHOR]

• Inorganic Cu 2 GeS 3 nanocrystals are utilized as hole transporting layer in C-PSCs. • Cu 2 GeS 3 could effectively extract photo-generated holes and suppress the charge carrier recombination. • C-PSC with a champion PCE of 19.0% is demonstrate. Hole transporting layer (HTL) is indispensable for promoting the power conversion efficiency (PCE) and device stability of perovskite solar cells (PSCs), especially for the carbon electrode based PSCs (C-PSCs). Compared with the large amount of organic HTLs, which are available for metal electrode based PSCs, the inorganic HTLs for C-PSCs are relatively scarce. In this study, we successfully synthesized Cu 2 GeS 3 nanocrystals with spherical shape and well dispersibility, and further explore their potential to function as inorganic HTL for C-PSCs. The Cu 2 GeS 3 HTL can greatly improve the PCE of C-PSCs to 19.0 %, which is enhanced by 36.3 % compared with that (PCE = 13.9 %) of HTL-free C-PSCs. The reported PCE in our study is among the highest PCEs for C-PSCs with inorganic HTL, therefore, our study indicates that Cu 2 GeS 3 nanocrystals are excellent inorganic HTL for C-PSCs. [ABSTRACT FROM AUTHOR]

• The double-perovskite oxide PrBa 0.5 Sr 0.5 Co 1.5 Fe 0.5 O 5+ δ (PBSCF) cathode maintains the better structural stability. • The mixed oxidation state of Pr3+/Pr4+, Co2+/Co3+, and Fe3+/Fe4+ species facilitate the oxygen reduction reaction kinetics. • Mössbauer Spectroscopy affirms that the proportion of Fe3+ and Fe4+ is 79.1 % and 20.9 %, respectively. • Low polarization resistance of 0.067 Ω cm−2 and high power density of 590 mW cm−2 at 800 °C are obtained on 300μm-thickness LSGM electrolyte. The physicochemical properties for layered perovskite PrBa 0.5 Sr 0.5 Co 1.5 Fe 0.5 O 5+ δ (PBSCF) oxide are systematically investigated to gain insight into the correlation between structure, surface state and oxygen reduction reaction properties. The PBSCF sample possesses orthorhombic structure and keeps better structural stability under operating conditions. X-ray photoelectron spectra analysis indicates that the mixed oxidation state of (Co, Fe) and Pr promotes the oxygen reduction reaction kinetics by creating oxygen vacancies at the surface. Mössbauer Spectroscopy affirms that the proportion of Fe3+ and Fe4+ in iron species is 79.1 % and 20.9 %, respectively. The electrode polarization resistance is 0.067 Ω cm2 at 800 °C in air. The oxygen-ion bulk diffusion plays the rate-limiting step during the electrode process. The cell with PBSCF cathode delivers the power density of 590 mW cm−2 at 800 °C. These results show the PBSCF exhibits a promising application prospect in intermediate temperature solid oxide fuel cell. [ABSTRACT FROM AUTHOR]

In recent years, 2D layered materials have been considered as promising photon absorption channel media for next-generation phototransistors due to their atomic thickness, easily tailored single-crystal van der Waals heterostructures, ultrafast optoelectronic characteristics, and broadband photon absorption. However, the photosensitivity obtained from such devices, even under a large bias voltage, is still unsatisfactory until now. In this paper, high-sensitivity phototransistors based on WS2 and MoS2 are proposed, designed, and fabricated with gold nanoparticles (AuNPs) embedded in the gate dielectric. These AuNPs, located between the tunneling and blocking dielectric, are found to enable efficient electron trapping in order to strongly suppress dark current. Ultralow dark current (10−11 A), high photoresponsivity (1090 A W−1), and high detectivity (3.5 × 1011 Jones) are obtained for the WS2 devices under a low source/drain and a zero gate voltage at a wavelength of 520 nm. These results demonstrate that the floating-gate memory structure is an effective configuration to achieve high-performance 2D electronic/optoelectronic devices. [ABSTRACT FROM AUTHOR]

Photoelectric conversion is realized by a series of processes in quantum-dot-sensitized solar cells (QDSSCs), including light capture, photoelectron generation, and electron transmission. In addition to obtaining photoelectrons, the photoanode provides a channel for electron transmission. Therefore, the photoanode plays important roles in improving the performances of QDSSCs. This paper presents the fabrication of a novel photoanode based on a semiconductor composite of ZnO nanorods and TiO 2 /ZnO inverse opal. QDSSCs with composite semiconductors of ZnO nanorods and oxide inverse opal in the photoanode were demonstrated to facilitate better charge transfer and reaction rates at the interface and obtain higher photocurrents and power conversion efficiencies than those of QDSSCs with pure inverse opal photoanodes. Using a CdS/CdSe co-sensitizer in the QDSSCs, a maximum cell efficiency of 8.18% was obtained, and it was further improved to 11.24% after interface modification with NH 4 F and ZnS. [ABSTRACT FROM AUTHOR]

• Oxides LnBaCo 2 O 5+δ (Ln = La, Pr, Nd and Sm) show different crystal symmetry. • Redox pair Co3+/Co4+ and oxygen vacancies concentration facilitate ORR activity. • The formation energy of oxygen vacancies and energy barrier of surface increase. • Polarization resistance increases with the decreasing Ln3+ radius. The structural characterization, surface state and electrochemical performances of LnBaCo 2 O 5+δ (LnBC) (Ln = La, Pr, Nd and Sm) perovskite cathode are systematically investigated for intermediate-temperature solid oxide fuel cells. The structural symmetry gradually distorts with the reduced ionic radius. The electrical conductivity decreases due to the increasing oxygen vacancy concentration from La to Sm. X-ray photoelectron spectroscopy analysis indicates that the concentration of oxygen active sites on the surface of LnBC samples decreases with shrinking Ln3+ radius. The increasing Ln–O bond energy leads to the reduction of the thermal expansion coefficients. The electrochemical performance of LnBC electrode decreases with the decreasing Ln3+ ionic radius. This result may be related to the decreasing. [ABSTRACT FROM AUTHOR]