Zhi Lei

Preparation of Cu2Te Thin Films and Back-Contact Formation of CdTe Solar Cells

Cu2Te thin films were prepared by a coevaporation method. The structural, optical, and electronic properties of Cu2Te thin films were investigated using X-ray diffraction, UV–visible–IR transmittance and reflectance spectra, and Hall measurements. The results show that single-phase Cu2Te thin films can be obtained after annealing at 170 °C, and that annealing temperatures higher than 200 °C induce the Cu2Te coexisting phase. Subsequently, CdTe solar cells with a Cu2Te layer were fabricated and annealed at various temperatures. CdTe solar cells with a single-phase hexagonal Cu2Te layer annealed at a temperature of 180 °C show a good ohmic-contact behavior.

Preparation and Characterization of Thin Films by Coevaporation

Deposition of thin films on soda-lime glass substrates by coevaporation of Sb and Te is described in this paper. thin films were characterized by x-ray diffraction (XRD), x-ray fluorescence (XRF), atomic force microscopy (AFM), x-ray photoelectron spectroscopy (XPS), electrical conductivity measurements, and Hall measurements. The abnormal electrical transport behavior occurred from in situ electrical conductivity measurements. The results indicate that as-grown thin films are amorphous and undergo an amorphous-crystalline transition after annealing, and the posttreatment can effectively promote the formation of Sb-Te bond and prevent oxidation of thin film surface.

AlSb THIN FILMS PREPARED BY DC MAGNETRON SPUTTERING AND ANNEALING

Aluminum antimonide (AlSb) is thought to be a potential material for high efficiency solar cells. In this paper, AlSb thin films have been fabricated by DC magnetron sputtering on glass substrates. The sputtering target consists of aluminum and antimony, and the area ratio of Al to Sb is 7:3, which is derived from research into the relationship between the deposition rates of both the metals and sputtering power. XRD and AFM measurements show that the as-deposited films are amorphous, but become polycrystalline with an average grain size of about 20 nm after annealing in an argon atmosphere. From optical absorption measurements of annealed AlSb films, a band gap of 1.56 eV has been demonstrated. Hall measurements show that the films are p-type semiconductors. The temperature dependence of dark conductivity tested in vacuum displays a linear lnσ to 1/T curve, which indicates a conductivity activation energy of around 0.61 eV.

STUDY ON AlSb POLYCRYSTALLINE THIN FILMS PREPARED BY VACUUM CO-EVAPORATION

In this paper, the AlSb polycrystalline thin films were prepared by vacuum co-evaporation technology and their structural, optical and electrical properties have been studied. XRD results showed that the as-deposited AlSb amorphous thin films transformed to polycrystalline state after annealed in vacuum at temperatures higher than 540°C. The process of phase change was observed to depend on the annealing temperature and the film composition. Some irreversible changes took place in the annealed films during the measurement of the temperature dependence of the film conductance. The conductance activation energy of the film was 0.132 and 0.32 eV during the heating and cooling process, respectively, which suggests the decrease of Sb vacancies in the AlSb film after the heating. Hall effect and optical absorption measurement showed that the AlSb polycrystalline thin films were p-type, indirect bandgap semiconductors with absorption coefficient higher than 8 × 104cm-1. TCO/CdS/AlSb photovoltaic devices with the local open circuit voltage of over 200 mV have been fabricated.

Produce Technology of CdTe Thin Film Modules and Design of Manufacture Line

Cadmium telluride thin films solar cells and modules have demonstrated high performance and low cost. After the efficiency of CdTe thin film solar cell made in Sichuan University reached 13.38%, a task of translation from the laboratory to pilot production of the solar cells has begun by us. The structure of the cells is CdS/CdTe/ZnTe/ZnTe:Cu. The front electrode is SnO2:F/HR-SnO 2 films on soda-lime glass and the metal as back electrode is Ni. This paper introduces the main manufacture technologies of our CdTe thin film solar modules with 300 mmtimes400 mm, explains the designs of the key equipments for 0.3 MW/year pilot manufacture line. According to the produce technologies implemented with the equipments, we estimate the costs of materials and modules. The result is that the cost of 1 W p CdTe PV module would be 1.8 dollar

Optical Constants of Cd0.8Zn0.2S Thin Films from Transmission Spectrum

Transmission spectrum of the Cd0.8Zn0.2S thin films prepared by vacuum evaporation, at normal incidence was obtained in the spectral region from 400 to 2000 nm. Based on the use of the maxima and minima of the interference fringes, a straightforward analysis proposed by Swanepoels method has been applied to derive the optical constants such as refractive index, n, absorption coefficients, a, optical band gap, Eg and the film thickness, d. The analysis of the optical absorption data revealed that the thin films were direct transition materials.

The Electrical and Optical Properties of CSS CDTE Thin Films Deposited in AR+O2 Atmosphere

The fabrication and properties of CdTe layer are most important to the performance of CdTe thin film solar cells, among their several function layers. In the paper, a technology of closed-space sublimation(CSS) in Ar+O2 atmosphere has been studied and a method of depositing CdTe thin films on smooth glass substrate has been developed. The structural properties of these films deposited in an appropriate CSS process have been investigated by XRD and SEM, which show that there are some changes by different abrading times. Then, the optical and electrical properties of CdTe films deposited on glass in different fractional pressure of O2 have been studied, and the effects of post-treatment on the properties are observed. These results have been used to prepared CdS/CdTe/ZnTe:Cu solar cells. FF of 70.3% and efficiency of 13.38% have been demonstrated for 0.501cm2 cell