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One of the unique characteristics of semiconductors is the strong dependence of their properties on crystal defects and doping. However, due to the species diversity and low density, it is very difficult to control the type and concentration of the defects. In perovskite materials, crystal defects are randomly formed during the fast crystallization process, causing large heterogeneity of the samples. Here, in this work, we report a controllable method to introduce surface defects on CH3NH3PbI3 perovskite materials via the interaction with 1,4-benzoquinone (BQ) molecules on the gas and solid interface. After the adsorption of BQ molecules on the perovskite surface, surface defects can be generated by photoinduced chemical reactions. The concentration of the defects can thus be controlled by precisely regulating the laser irradiation time. The concentration of the defects can be characterized by a gradually decreased PL intensity and lifetime and was found to influence the atmospheric response and the subsequent acetone-induced degradation of the materials. These results demonstrate that crystal defects in perovskite materials can be controllably introduced, which provides a possible way to fully understand the correlation between the nature and chemical structure of these defects. [ABSTRACT FROM AUTHOR]

Inorganic perovskite materials have attracted broad interest in the last several years due to their stability and promising applications as photovoltaic and light‐emitting materials. In this work, we prepared Cs4PbBr6 nanoparticles showing stable photoluminescence (PL) without blinking and studied the PL properties of individual Cs4PbBr6 nanoparticles in the biological temperature range. We found that both PL intensity and lifetime of a single Cs4PbBr6 particle strongly depends on the temperature. The PL intensity and lifetime decrease almost linearly with the increasing of the temperature. The slopes of the PL intensity and lifetime versus temperature were as high as 2% and 3% per degree centigrade, respectively. The photostability and thermal stability were also checked for individual particles. With these results, we proposed that the sensitivity of PL intensity and lifetime of a single Cs4PbBr6 nanoparticle on temperature showed the potential application of a single particle as a nanothermometer for thermal detection in a local environment. Take the temperature: Non‐blinking Cs4PbBr6 nanoparticles show potential as a single‐particle thermometers to detect local temperatures on the nanometer scale. [ABSTRACT FROM AUTHOR]

Solution-processed organometal halide perovskites (OMHPs) have been widely used in optoelectronic devices, and have exhibited brilliant performance. One of their generally recognized advantages is their easy fabrication procedure. However, such a procedure also brings uncertainty about the opto-electric properties of the final samples and devices, including morphology, stability, coverage ratio, and defect concentration. Normally, one needs to find a balanced condition, because there is a competitive relation between these parameters. In this work, we fabricated CH3NH3PbI3 films by carefully changing the ratio of the PbI2 to CH3NH3I, and found that the stoichiometric and solvent engineering not only determined the photoluminescence efficiency and defects in the materials, but also affected the photostability, morphology, and coverage ratio. Combining solvent engineering and the substitution of PbI2 by Pb(Ac)2, we obtained an optimized fabrication condition, providing uniform CH3NH3PbI3 films with both high photoluminescence efficiency and high photostability under either I-rich or Pb-rich conditions. These results provide an optimized fabrication procedure for CH3NH3PbI3 and other OMHP films, which is crucial for the performance of perovskite-based solar cells and light emitting devices. [ABSTRACT FROM AUTHOR]

All-inorganic metal halide perovskite nanocrystals (NCs) have been exceptional candidates for high-performance solution-processed optoelectronic and photonic devices compared with organometal halide perovskite NCs due to their superior stability. However, the interactions between all-inorganic perovskite NCs and moisture, which is an acknowledged detrimental factor, are still under debate, and detailed investigations to uncover such fundamentals remain to be performed. Herein, with wide-field fluorescence microscopy, the burst photoluminescence blinking responses of CsPbBr 3 NCs were observed in ambient air, and moisture rather than oxygen was verified to be the key factor that leads to the enhanced PL intensity and reduced OFF duration. This behavior is rationalized through an effective passivation effect of the adsorbed water molecules on the surface halide vacancies on CsPbBr 3 NCs. This work validates that ∼40% humidity atmospheres are helpful for better utilizing the all-inorganic perovskites, which is evidence of their promising prospect for application.

Organometal halide perovskites (OMHPs) have emerged as advisible materials for application in optoelectronic devices over the past decade. However, a variety of complex slow responses in OMHPs under an external electric field have been observed, and the mechanisms for these responses remain a topic of intense debate. In this work, with an external voltage applied to the CH 3 NH 3 PbI 3 crystal, reversible photoluminescence (PL) enhancement and quenching behaviors respectively near the anode and the cathode were observed under wide-field fluorescence microscopy. Further experiments attribute the reversible PL enhancing responses to the electron injection effect increasing the radiative recombination, while PL quenching was attributed to be due to the electron extraction effect increasing the nonradiative recombination. The control of PL by external applied voltage indicates brilliant carrier mobility in the CH 3 NH 3 PbI 3 crystal and also reminds us to focus on the effect of hole/electron injection on the materials which may limit the performance of perovskite-based optoelectronic devices.

Two-dimensional (2D) perovskites are attracting broad attention for their stability and wavelength tunability. However, random crystallization of sample preparation makes it difficult to obtain 2D perovskites with pure structure, especially when the number of layers is large. Herein, we prepared 2D perovskite (C 8 H 17 NH 3 ) 2 (MA) n -1 Pb n I 3 n +1 with different layers ( n = 1-10). For the first time, we experimentally identified the band gap energy  E g of 2D perovskite (C 8 H 17 NH 3 ) 2 (MA) n -1 Pb n I 3 n +1 with layers up to 10 by investigating specific pieces of crystal with pure emission spectra using fluorescence microscopy. Intriguingly, the relationship between E g and n perfectly fits an exponential function rather than the pure quantum confinement effect in good agreement with the theoretical calculation based on first principles. Our results suggest that the band gap of the 2D perovskite is determined not only by quantum confinement effect, but other factors including chemical components also give significant contribution.

Solar-driven photocatalytic overall water splitting is regarded as one of the ideal strategies to generate renewable hydrogen energy without the initiation of environmental issues. However, there are still a few remaining challenges to develop wide-light-absorption and stable photocatalysts for the simultaneous production of H2 and O2 in pure water without sacrificial reagents. Herein, we report the design and preparation of Z-scheme TiO2/ZnTe/Au nanocorncob heterojunctions by homogeneously decorating Au nanoparticles onto the surface of core-shell TiO2/ZnTe coaxial nanorods for highly efficient overall water splitting. With the appropriate band structure of TiO2/ZnTe heterojunctions and the surface plasmon resonance enhancement of Au nanoparticles, the well-designed TiO2/ZnTe/Au nanocorncob heterojunctions can synergistically make effective utilization of broad-range solar light illunimation and enhance the separation efficency of electron-hole pairs, as evidenced by UV-Vis absorption and time-resolved photoluminescence spectroscopy. Photoelectrochemical characterization confirms that the water-splitting reaction on TiO2/ZnTe/Au nanocorncobs is mainly carried out via a two-electron/two-electron transfer process with an intermediate product of H2O2. As a result, the TiO2/ZnTe/Au nanocorncob photocatalyst can generate H2 and O2 with a stoichiometric ratio of 2 : 1 under light irradiation without any sacrificial agents, exhibiting a high H2 production rate of 3344.0 μmol g-1 h-1 and a solar-to-hydrogen (STH) efficiency of 0.98%. Moreover, the TiO2/ZnTe/Au nanocorncob heterojunctions show high stability and well-preserved morphological integrity after long-term photocatalytic tests. This study provides a prototype route to produce clean hydrogen energy from only sunlight, pure water, and rationally-designed heterojunction photocatalysts.