Characterization of CdS Thin-Film in High Efficient CdS/CdTe Solar Cells

Abstract

Cadmium sulfide (CdS) thin films are the most commonly used window materials for high efficient cadmium telluride (CdTe) and chalcopyrite polycrystalline thin-film photovoltaic devices. High efficient CdS/CdTe solar cells with thin CdS films have been developed using ultrathin CdS films with a thickness of less than 0.1 µm. CdS films were deposited on transparent conductive oxide (TCO)/glass substrates by the metal organic chemical vapor deposition (MOCVD) technique. CdTe films were subsequently deposited by the close-spaced sublimation (CSS) technique. The screen printing and sintering method fabricated carbon and silver electrodes. Cell performance depends primarily on the electrical and optical properties of CdS films. Therefore we started to develop higher-quality CdS films and found clear differences between high- and low-quality CdS films from the analyses of scanning electron microscope (SEM), atomic force microscope (AFM), secondary ion mass spectroscopy (SIMS), thermal desorption spectrometry (TDS) and Fourier transforms-infrared spectrometry (FT-IR) measurements. As a result of controlling the quality of CdS films, a photovoltaic conversion efficiency of 10.5% has been achieved for size of 1376 cm2 of the solar cells under the Air Mass (AM) 1.5 conditions of the Japan Quality Assurance Organization.

Nanocomposites for Photovoltaic Energy Conversion

“…MOCVD is a common process for thin film solar cell deposition. It can be used on TCO, buffer layer and absorber layer, such as SnO 2 (Ferekides et al, 2000), CdS (Matsune et al, 2006;Kato et al, 2001;Tsuji et al, 2000), ZnO (Hariskos et al, 2005;Ennaoui et al, 2001) and CdTe (Sharma et al, 2003) etc. There are also other type of CVD for different materials.…”

“…The close space sublimation (CSS) is widely used in CdS (and similar semiconductors) and CdTe thin film deposition in CdTe solar cells (Matsune et al, 2006;Kumazawa et al, 1997;Aramoto et al, 2003;Tsuji et al, 2000;Britta & Ferekides., 1993;Dzhafarov et al, 2005;Enrıquez et al, 2007;Khrypunov et al, 2006;Okamotoet al, 2000;Dhere et al, 1997;Ferekides et al, 2000). CSS is an attractive process and has many advantages.…”

“…Cell performance depends primarily on the electrical and optical properties of CdS film. The deep research shows the conversion efficiency of CdS/CdTe solar cells strongly depends on the ruggedness of the CdS surface (Tsuji et al, 2000). CdS is an n-type semiconductor.…”

“…The optimum band gap is ~2.4 eV for solar spectrum and the direct band gap yields high optical absorption coefficient. CdS can be deposited by many methods such as CSS (Luschitz et al, 2009), MOCVD (Matsune et al, 2006;Tsuji et al, 2000), CVD (Kumazawa et al, 1997), magnetron sputtering , chemical bath deposition (CBD) and vacuum evaporation (Lee, 2005). Much research has been performed on CdS/CdTe solar cells and very high energy conversion efficiencies have been achieved ( Morales-Acevedo (Morales-Acevedo, 2006) has made a physical analysis of the typical CdS-/CdTe superstrate solar cell.…”

Growth of AgGaTe2 Layers by a Closed-Space Sublimation Method

“…[1][2][3][4][5][6][7] Also, chalcopyrite I-III-VI 2 compounds have recently attracted attention as potential components for semiconductor devices, including applications in solar cells and electrooptic devices. [8][9][10] In particular, CuInSe 2 has already become widely used in making commercial solar cells.…”