Cheng Shuying

Photoelectric properties of Cu2ZnSnS4 thin films deposited by thermal evaporation

Sn/Cu/ZnS precursor were deposited by evaporation on soda lime glass at room temperature, and then polycrystalline thin films of Cu2ZnSnS4 (CZTS) were produced by sulfurizing the precursors in a sulfur atmosphere at a temperature of 550 °C for 3 h Fabricated CZTS thin films were characterized by X-ray diffraction, energy dispersive X-ray spectroscopy, ultraviolet-visible-near infrared spectrophotometry, the Hall effect system, and 3D optical microscopy. The experimental results show that, when the ratios of [Cu]/([Zn] + [Sn]) and [Zn]/[Sn] in the CZTS are 0.83 and 1.15, the CZTS thin films possess an absorption coefficient of larger than 4.0 × 104 cm−1 in the energy range 1.5–3.5 eV, and a direct band gap of about 1.47 eV. The carrier concentration, resistivity and mobility of the CZTS film are 6.98 × 1016 cm−3, 6.96 Ωcm, and 12.9 cm2/(Vs), respectively and the conduction type is p-type. Therefore, the CZTS thin films are suitable for absorption layers of solar cells.

Photoelectric properties of ITO thin films deposited by DC magnetron sputtering

As anti-reflecting thin films and transparent electrodes of solar cells, indium tin oxide (ITO) thin films were prepared on glass substrates by DC magnetron sputtering process. The main sputtering conditions were sputtering power, substrate temperature and work pressure. The influence of the above sputtering conditions on the transmittance and conductivity of the deposited ITO films was investigated. The experimental results show that, the transmittance and the resistivity decrease as the sputtering power increases from 30 to 90 W. When the substrate temperature increases from 25 to 150 °C, the transmittance increases slightly whereas the resistivity decreases. As the work pressure increases from 0.4 to 2.0 Pa, the transmittance decreases and the resistivity increases. When the sputtering power, substrate temperature and work pressure are 30 W, 150 °C, 0.4 Pa respectively, the ITO thin films exhibit good electrical and optical properties, with resistivity below 10−4 Ωcm and the transmittance in the visible wave band beyond 80%. Therefore, the ITO thin films are suitable as transparent electrodes of solar cells.

Substrate temperature effects on the structural and photoelectric properties of ZnS:In films

Indium doped ZnS (ZnS:In) films were prepared on glass substrate using thermal evaporation technology. It was found that the structural, optical and electrical properties of ZnS:In films strongly depend on the substrate temperature (Ts). By X-ray diffraction (XRD), atomic force microscopy (AFM), transmittance spectroscopy, and electric performance measurements, the effect of Ts on ZnS:In film is studied in detail. It reveals that Ts has important effect on ZnS grain size, crystallinity, lattice disorder, etc., which further leads to the obvious influence on its optical and electrical performance. Under the optimized Ts, the performance, especially the conductivity, achieved in this work is far higher than that reported for other n-type ZnS films.

Remote Monitoring and Control System of Solar Street Lamps Based on ZigBee Wireless Sensor Network and GPRS

In order to avoid the shortcomings and deficiencies of solar street lamp systems at present market, in this paper, a new kind of solar street lamps monitoring & control system is designed. By combining ZigBee technology with MPPT algorithm in the design of solar street lamp controller, the wireless monitoring network can be constituted by solar lamps themselves, and the conversion efficiency of solar energy is improved. The working state of solar lamps distributed in one area can be monitored and controlled by the remote monitoring center through GPRS and Internet. The system consists of three main parts: solar street lamp controller, ZigBee wireless network, remote monitoring center. By designing the system hardware and software, and testing the experimental result, it is proven that the system is highly reliable, cost-effective, low power consumption, fast establishing and has a broad application prospect.