Growth and characterization of CdZnS thin film buffer layers by chemical bath deposition
In this paper we report the study of CdZnS thin films grown on the soda-lime glass (SLG) substrates by chemical bath deposition (CBD) process for buffer layer applications in CuGaSe/sub 2/ (CGS) solar cells. Structural, surface morphology, optical, and electrical properties of as-deposited CdZnS films were investigated by XRD, SEM, spectrophotometer, and four probes resistivity measurements as a function of Zn-composition in the solution. The CdZnS films have hexagonal structures. The grain size of CdZnS films was found to increase with increasing Zn-content in the solution. The films with 30% of Zn in the solution showed a better than 80% transmittance for wavelengths longer than 600 nm and film thickness less than 50 nm. The values of energy band gaps obtained are 2.40, 2.55, and 2.70 eV for Zn-content of 0, 30, and 50%, respectively. The resistivity of CdZnS films was found to increase as the Zn content increases.
Polycrystalline CuGaSe2 thin film solar cells
Abstract Thin films of CuGaSe2 were prepared on Cominf 7059 glass substrates by employing laser, flash and electron beam evaporation techniques. The physical properties of the films deposited with these techniques were studied and compared. Thin film heterojunction solar cells were fabricated using CdS, ZnCdS and ZnO as window materials and CuGaSe2 as an absorber. The current-voltage and capacitance-voltage characteristics of the junctions were studied to evaluate the junction parameters and photovoltaic properties. An efficiency of 4.9% was observed for a ZnCdS/CuGaSe2 heterojunction. An enhanced spectral response in the high-energy region was observed in the case of the ZnO/CuGaSe2 junction.
Current‐voltage transients in (Cd,Zn)S/CuInSe2 solar cells
Transients in the current‐voltage characteristics of (Cd,Zn)S/CuInSe2 solar cells after sudden changes in illumination are reported. The transients are found to vary with bias across the cell, intensity, temperature, illumination wavelength, and recent illumination history. Multiple trapping levels, primarily in the CuInSe2 near the interface, are seen as responsible for the observed dc voltage shift and are photoexcited in less than 1 ms. Relaxation in the dark takes tens of seconds and appears dominated by states in the (Cd,Zn)S which gives wavelength dependent effects on fill factor and transient decay.