Zhiwen Qiu

Near Room Temperature, Fast-Response, and Highly Sensitive Triethylamine Sensor Assembled with Au-Loaded ZnO/SnO2 Core–Shell Nanorods on Flat Alumina Substrates

Chemiresistive gas sensors with low power consumption, fast response, and reliable fabrication process for a specific target gas have been now created for many applications. They require both sensitive nanomaterials and an efficient substrate chip for heating and electrical addressing. Herein, a near room working temperature and fast response triethylamine (TEA) gas sensor has been fabricated successfully by designing gold (Au)-loaded ZnO/SnO2 core-shell nanorods. ZnO nanorods grew directly on Al2O3 flat electrodes with a cost-effective hydrothermal process. By employing pulsed laser deposition (PLD) and DC-sputtering methods, the construction of Au nanoparticle-loaded ZnO/SnO2 core/shell nanorod heterostructure is highly controllable and reproducible. In comparison with pristine ZnO, SnO2, and Au-loaded ZnO, SnO2 sensors, Au-ZnO/SnO2 nanorod sensors exhibit a remarkably high and fast response to TEA gas at working temperatures as low as 40 °C. The enhanced sensing property of the Au-ZnO/SnO2 sensor is also discussed with the semiconductor depletion layer model introduced by Au-SnO2 Schottky contact and ZnO/SnO2 N-N heterojunction.

Oxygen influencing the photocarriers lifetime of CH3NH3PbI3−xClx film grown by two-step interdiffusion method and its photovoltaic performance

During the growth of CH3NH3PbI3−xClx (MAPbI3−xClx) perovskite films by the two-step inter-diffusion method, the presence of a trace amount of oxygen gas is critical to their physical properties and photovoltaic performance. As the oxygen concentration increases, poor film morphologies and incomplete surface coverage are observed. Moreover, by XRD, Raman scattering, and photoluminescence measurements, we find that MAPbI3−xClx grains become more distorted and the electron-hole recombination rate dramatically increases. Higher oxygen concentration triggers a sharp decrease in the current density and the fill factor of corresponding solar cells, which degrades device performance, on average, from 14.3% to 4.4%. This work proves the importance of controlling the oxygen atmosphere in the fabrication of high-performance perovskite solar cells.

High-Quality Perovskite Films Grown with a Fast Solvent-Assisted Molecule Inserting Strategy for Highly Efficient and Stable Solar Cells

The performance of organolead halide perovskites based solar cells has been enhanced dramatically due to the morphology control of the perovskite films. In this paper, we present a fast solvent-assisted molecule inserting (S-AMI) strategy to grow high-quality perovskite film, in which the methylammonium iodide/2-propanol (MAI/IPA) solution is spin-coated onto a dimethylformamide (DMF) wetted mixed lead halide (PbX2) precursor film. The DMF can help the inserting of MAI molecules into the PbX2 precursor film and provide a solvent environment to help the grain growth of the perovskite film. The perovskite film grown by the S-AMI approach shows large and well-oriented grains and long carrier lifetime due to the reduced grain boundary. Solar cells constructed with these perovskite films yield an average efficiency over 17% along with a high average fill factor of 80%. Moreover, these unsealed solar cell devices exhibit good stability in an ambient atmosphere.

Growth temperature-dependent performance of planar CH3NH3PbI3 solar cells fabricated by a two-step subliming vapor method below 120 °C

Using an extremely simple but promising two-step sequential subliming vapor deposition method, we grow high-quality perovskite CH3NH3PbI3 films with a uniform and continuous surface coverage. The perovskite film morphology and growth orientation can be well controlled by the growth temperature. The temperature influence on the power conversion efficiency (PCE) and the current–voltage hysteresis of the Spiro/CH3NH3PbI3/TiO2 P-i-N planar film solar cells is also investigated. Furthermore, a novel solvent annealed PCBM film was introduced between the TiO2 compact layer and perovskite active layer, which not only reduces the J–V hysteresis obviously but also enhances device performance. After optimization of the fabrication temperature and device structure, it was found that the PCEs of the solar cells fabricated at 120 °C on glass and flexible PET substrates can reach 15.59% and 7.62%, respectively. This promising approach provides a way to construct low-cost and large-area perovskite cell devices.

Performance Improvement of Ultraviolet Sensor of ZnO Nanorod Arrays

In this letter, large-area, high-quality, evenly distributed, and vertically oriented Na-doped ZnO nanorod arrays (NRAs:Na) are prepared by chemical vapor deposition. The properties of the relevant ultraviolet sensors are studied, indicating that by providing an intrinsic ZnO coating via the hydrothermal method and annealing treatment, the performance of the sensors could be improved dramatically. Photoluminescence analyses show that Na doping suppressed the green emission of NRAs:Na, which is commonly ascribed to the singly VO located at the surface of the nanorods. For the optimized NRAs:Na sensors with a core–shell structure, the VO–Oi annihilation mechanism is proposed to interpret the reduction of the persistent photocurrent.