Jingzhen Shao

Roughness evolution of ZrO2 thin films grown by reactive ion beam sputtering

A series of zirconium dioxide films were grown on rough borosilicate crown glass substrates with reactive ion beam sputtering technique. The evolution of the surface roughness was studied in the smoothing and roughening growth regimes using atomic force microscopy. By quantitative analysis of surface morphology, the interface width of the growth fronts was found to have a minimum during the deposition process. Dynamic scaling was observed for thicker films; the roughness exponent was found to be in the range of 0.7–0.9 and the growth exponent at approximately 0.4.

Fabrication and electrical properties of p-CuAlO2/(n-, p-)Si heterojunctions

CuAlO2 thin films have been prepared by the chemical solution deposition method on both n-Si and p-Si substrates. X-ray diffraction analysis indicates that the obtained CuAlO2 films have a single delafossite structure. The current transport properties of the resultant p-CuAlO2/n-Si and p-CuAlO2/p-Si heterojunctions are investigated by current–voltage measurements. The p-CuAlO2/n-Si has a rectifying ratio of ~35 within the applied voltages of −3.0 to +3.0 V, while the p-CuAlO2/p-Si shows Schottky diode-like characteristics, dominated in forward bias by the flow of space-charge-limited current.

Room temperature deposition of amorphous p-type CuFeO2 and fabrication of CuFeO2/n-Si heterojunction by RF sputtering method

Transparent conducting amorphous p-type CuFeO2 (CFO) thin film was prepared by radio-frequency (RF) magnetron sputtering method at room temperature using polycrystalline CuFeO2 target. Amorphous structure of as-deposited film was confirmed by XRD. XPS analysis convinced that the chemical state of Cu+ and Fe3+ in the film, and the chemical composition of the thin films is close to the stoichiometry of CuFeO2. Surface morphology of the film was analysed by SEM studies. p-type nature and concentration of carriers was investigated by Hall effect measurement. The p–n heterojunction in the structure of Al/n-Si/p-CuFeO2/Al showed good rectifying behaviour with a forward and reverse currents ratio of 555 at 2 V. The turn-on voltage and reverse leakage current values were found to be 0.9 V and 4 μA at −2 V. Further, the conduction mechanism of forward bias voltage was controlled by thermionic emission (TE) and trap-space charge limited current (TCLC) mechanisms.

Optimization of photoelectrode for flexible dye-sensitized solar cell and preliminary study of tandem cell

Based on the preparation of flexible dye-sensitized solar cells(DSC) by cold isostatic pressing method,optimization of the paste and tandem DSC were investigated.The results presented that hydrothermal treatment of P25 paste could improve the stability of the paste and the efficiency of DSC obviously.Proper amount of 200 nm TiO2particles was added to the P25 paste to enhance light scattering of photoelectrode.The highest conversion efficiency of 3.11% was obtained at the 4:1 ratio of P25 to 200 nm TiO2.Subsequently,N719 and N749 double-layer tandem DSC were studied.The results show that the efficiency of the double-layer tandem DSC is higher than that of N749 totally sensitized DSC but lower than that of N719 totally sensitized DSC.This may be caused by that thicker photoelectrode hampers the electronic transmission and dyes contact impacts the purity of dyes.The thickness of photoelectrode and cell structure need to be optimized.

Oxygen Vacancy Defects Boosted High Performance p-Type Delafossite CuCrO2 Gas Sensors

p-type ternary oxides can be extensively explored as alternative sensing channels to binary oxides with diverse structural and compositional versatilities. Seeking a novel approach to magnify their sensitivities toward gas molecules, e.g., volatile organic compounds (VOCs), will definitely expand their applications in the frontier area of healthcare and air-quality monitoring. In this work, delafossite CuCrO2 (CCO) nanoparticles with different grain sizes have been utilized as p-type ternary oxide sensors. It was found that singly ionized oxygen vacancies (Vo•) defects, compared with the grain size of CCO nanoparticles, play an important role in enhancing the charge exchange at the VOCs molecules/CCO interface. In addition to suppressing the hole concentration of the sensor channel, the unpaired electron trapped in Vo• provides an active site for chemisorptions of environmental oxygen and VOCs molecules. The synergetic effect is responsible for the observed increase of sensitivity. Furthermore, the sensitive (Vo• defect-rich) CCO sensor exhibits good reproducibility and stability under a moderate operation temperature (<325 °C). Our work highlights that Vo• defects, created via either in situ synthesis or postannealing treatment, could be explored to rationally boost the performance of p-type ternary oxide sensors.