Excellent color purity with a tunable band gap renders organic-inorganic halide perovskite highly capable of performing as light-emitting diodes (LEDs). Perovskite nanocrystals show a photoluminescence quantum yield exceeding 90%, which, however, decreases to lower than 20% upon formation of a thin film. The limited photoluminescence quantum yield of a perovskite thin film has been a formidable obstacle for development of highly efficient perovskite LEDs. Here, we report a method for highly luminescent MAPbBr (MA = CHNH) nanocrystals formed in situ in a thin film based on nonstoichiometric adduct and solvent-vacuum drying approaches. Excess MABr with respect to PbBr in precursor solution plays a critical role in inhibiting crystal growth of MAPbBr, thereby forming nanocrystals and creating type I band alignment with core MAPbBr by embedding MAPbBr nanocrystals in the unreacted wider band gap MABr. A solvent-vacuum drying process was developed to preserve nanocrystals in the film, which realizes a fast photoluminescence lifetime of 3.9 ns along with negligible trapping processes. Based on a highly luminescent nanocrystalline MAPbBr thin film, a highly efficient green LED with a maximum external quantum efficiency of 8.21% and a current efficiency of 34.46 cd/A was demonstrated.

We report on reduced graphene oxide (rGO)/mesoporous (mp)-TiO2 nanocomposite based mesostructured perovskite solar cells that show an improved electron transport property owing to the reduced interfacial resistance. The amount of rGO added to the TiO2 nanoparticles electron transport layer was optimized, and their impacts on film resistivity, electron diffusion, recombination time, and photovoltaic performance were investigated. The rGO/mp-TiO2 nanocomposite film reduces interfacial resistance when compared to the mp-TiO2 film, and hence, it improves charge collection efficiency. This effect significantly increases the short circuit current density and open circuit voltage. The rGO/mp-TiO2 nanocomposite film with an optimal rGO content of 0.4 vol % shows 18% higher photon conversion efficiency compared with the TiO2 nanoparticles based perovskite solar cells.

The effect of the doping configuration and concentration of nitrogen (N) and sulfur (S) on the electrochemical performance of 3 D N and S co-doped hole defect graphene hydrogel (NS-HGH) electrodes is investigated. Surprisingly, by introducing a hole defect on the graphene surface, the difference in the doping concentrations of N and S can be used to effectively modulate the electrochemical behavior of the NS-HGH. The hole defects provide a rapid ion diffusion path. Finally, we showed that the intriguing specific capacitance (536 F g(-1) ) of the NS-HGH could enhance the overall performance of the pseudocapacitance and electric double layer capacitance. The rational design of the NS-HGH-based flexible solid state supercapacitor results in not only outstanding electrochemical performance with a maximum energy density of 14.8 Wh kg(-1) and power density of 5.2 KW kg(-1) but also in extraordinary mechanical flexibility and excellent cycle stability.

We developed a method to improve the electrical performance and stability of passivated amorphous In-Ga-Zn-O thin-film transistors by simultaneous ultraviolet and thermal (SUT) treatment. SUT treatment was carried out on fully fabricated thin-film transistors, including deposited source/drain and passivation layers. Ultraviolet (UV) irradiation disassociated weak and diatomic chemical bonds and generated defects, and simultaneous thermal annealing rearranged the defects. The SUT treatment promoted densification and condensation of the channel layer by decreasing the concentration of oxygen-vacancy-related defects and increasing the concentration of metal-oxide bonds. The SUT-treated devices exhibited improved electrical properties compared to nontreated devices: field-effect mobility increased from 5.46 to 13.36 V·s, sub-threshold swing decreased from 0.49 to 0.32 V/decade, and threshold voltage shift (for positive bias temperature stress) was reduced from 5.1 to 1.9 V.

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