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This study reports the performances of a single structured light-emitting diode (LED) devices based on polymer material poly(9,9-di- n -hexylfluorenyl-2,7-diyl) (PHF) mixed with various concentrations of perovskite oxide strontium titanate (SrTiO3) particles deposited as a composite PHF: SrTiO3 emitting layer. The performances of the single structured organic LED indium tin oxide (ITO)/PHF/aluminum (Al) device and the composite LED ITO/PHF: SrTiO3/Al devices were compared in terms of turn-on voltage and luminance intensity. By incorporating perovskite SrTiO3 particles into PHF emitting layer, the turn-on voltage of the device is significantly reduced from 11.25 V to 1.80 V and the luminance intensity increased from 57.7 cd/m2 to 609 cd/m2. The improvement of turn-on voltage and the electroluminescence spectrum of the composite devices were found to be dependent on the weight ratios of SrTiO3 content in the PHF emitting layer. [ABSTRACT FROM AUTHOR]

The structure and the electronic properties of the electron‐transport layer (ETL) of perovskite solar cells (PSCs) govern the interfacial charge transfer and charge transportation to the electrode. The ETLs of two dimensions, that are atom thick, and have a planar structure that possesses special electronic properties, such as the surface collective motion of excitons or charge transfer–driven defect state relief, that is 2D transition metal dichalcogenide, allow a highly energetic carrier dynamic process for enhanced photovoltaic effect. Herein, it is discovered that planar, few‐atom‐thick 2H–WS2 nanosheets' ETLs drive ultrafast charge transfer and transportation along the ETL during the photovoltaic process. Time‐resolved photoluminescence and electrochemical impedance spectroscopy analysis results indicate that the charge transfer from the perovskite to the ETL occurs as fast as 5.9 ns with charge transfer resistance as low as 25.6 Ω. This allows the PSC device to produce a power conversion efficiency of 18.21% with short‐circuit current density, open‐circuit voltage, and fill factor as high as 22.24 mA cm2, 1.12 V, and 0.731, respectively. The PSC retains 96.87% of its performance when being aged in nitrogen atmosphere for 33 days. Atom‐thick planar WS2 ETL nanosheets can be the basis for the development of high‐performance PSC devices. [ABSTRACT FROM AUTHOR]

Lead halide perovskites have demonstrated outstanding achievements in photoelectric applications owing to their unique properties. However, the moisture sensitivity of lead halide perovskite has rarely been developed into an applicable humidity sensor due to the intrinsic instability and toxicity issue. Herein, as a highly stable lead‐free perovskite, a Cs2BiAgBr6 thin film is chosen to be the active material for humidity sensor due to its extraordinary humidity‐dependent electrical properties and good stability. This Cs2BiAgBr6 thin film humidity sensor demonstrates a superfast response time (1.78 s) and recovery time (0.45 s). The superfast response and recovery properties can be attributed to the reversible physisorption of water molecules, which can be easily adsorbed onto or desorbed from the thin film surface. Moreover, the sensor also shows an excellent reliability and stability properties as well as logarithmic linearity in a relative humidity's range of 15% to 78%. The lead‐free Cs2BiAgBr6 perovskite possesses great potential for application in real‐time humidity sensing. [ABSTRACT FROM AUTHOR]

The structure and crystallinity of the photoactive materials in solar cell determines the exciton formation, carrier’s recombination, life-time and transportation in the devices. Here, we report that enhanced charge transportation, internal quantum efficiency and the carrier life-time can be achieved by modifying the structure, morphology of the organic perovskite thin film, enabling the improvement of the solar cell performance. The thin film structure modification was achieved via a thermal annealing in vacuum. In typical procedure, the power conversion efficiency of the PSC device can be upgraded from 0.5 to 2.9%, which is approximately 6 times increment, when the surface structure disorders are limited in the organic perovskite thin film. By optimizing the organic perovskite loading on the Ga-TiO2 diatom-like nanostructures photoanode and combining with a fine control of organic perovskite thin film structure, power conversion efficiency as high as 6.58% can be generated from the device. Electrochemical impedance spectroscopy and current-voltage analysis in the dark indicated that this process has effectively augmented the carrier life-time and limited the carrier recombination, enhancing the overall performance of the solar cell device. The preparation process and mechanism of the device performance improvement will be discussed. [ABSTRACT FROM AUTHOR]

Metal doping on the anatase TiO 2 produces many effect including narrowing the band gap and creates a mid-gap state for facile carrier transport in the structure. This paper reports the study on the effect of Ga doping on the photoactivity of TiO 2 microtablet in the perovskite sensitive solar cell (PSC). It was found that the Ga doping enhances the interfacial characteristic between TiO 2 and perovskite layer as well as the carrier transport in the device. The power conversion efficiency of the PSC device can be improved from 0.23 to 2.46% upon the doping of Ga in the TiO 2 microtablet system. Detailed preparation process and mechanism of the device performance improvement will be discussed. [ABSTRACT FROM AUTHOR]

The addition of additives into the perovskite system to increase humid stability can reduce the crystallinity and deteriorate the optoelectrical properties of the perovskite. Here, we modify the crystallinity properties of hexamined MAPbI 3 perovskite, a humid-resistant perovskite, by adding penethylammonium iodide (PEAI) molecules to the perovskite system. XRD analysis result suggests that the PEAI causes a significant contraction in perovskite's lattice, which in turn could reconfigures the electronics structure of the perovskite. We found that PEAI succeeded in increasing the grain size from 120 ± 15 nm in pristine perovskite to 180 ± 20 nm in optimum sample (PEAI 1.0) and the compactness of the grain of the film, reducing the trap density from 2.98 × 1022/cm3 in pristine sample to 1.13 × 1022/cm3 in optimum sample, and thereby enabling enhanced carrier dynamics at the interface and the bulk structure of the device. We found that the perovskite solar cells device fabricated using this new perovskite system can produce power conversion efficiency as high as 15.75%, which is an increase of as high as 55% than the control device. These findings may become a potential alternative to improve the optoelectrical properties of the perovskite materials. Penetylammonium ion additive improves the crystallinity properties of the humid stable MAPbI 3 perovskite, enhancing the carrier dynamic in the device. [Display omitted] • Penetylammonium cation improves the crystallinity of hexamined-MAPbI 3 perovskite. • The additive reduces the carrier trap, enhancing carrier dynamic in the device. • The additive improves the power conversion efficiency. [ABSTRACT FROM AUTHOR]