Polycrystalline thin-film solar cell

PEC Setup Cell Combining Polycrystalline Thin-Film Solar Cells and Photoanodes... 

PEC cell that uses polycrystalline thin-film solar cells with a photoanode. 

Banger, K. K. Hollingsworth, J. A. Harris, J. D. Cowen, J. Buhro, W. E. Hepp, A. F. 2002. Ternary single-source precursors for polycrystalline thin-film solar cells. Appl. Organomet. Chem. 16 617-627. 

Contreas, M. Egaas, B. Ramanathan, K. 1999. Progress toward 20% efficiency in Cu(In,Ga)Se2 polycrystalline thin-film solar cells. Prog. Photovolt. Res. App. 7 311-316. 

Water is involved in most of the photodecomposition reactions. Hence, nonaqueous electrolytes such as methanol, ethanol, N,N-d i methyl forma mide, acetonitrile, propylene carbonate, ethylene glycol, tetrahydrofuran, nitromethane, benzonitrile, and molten salts such as A1C13-butyl pyridium chloride are chosen. The efficiency of early cells prepared with nonaqueous solvents such as methanol and acetonitrile were low because of the high resistivity of the electrolyte, limited solubility of the redox species, and poor bulk and surface properties of the semiconductor. Recently, reasonably efficient and fairly stable cells have been prepared with nonaqueous electrolytes with a proper design of the electrolyte redox couple and by careful control of the material and surface properties [7], Results with single-crystal semiconductor electrodes can be obtained from table 2 in Ref. 15. Unfortunately, the efficiencies and stabilities achieved cannot justify the use of singlecrystal materials. Table 2 in Ref. 15 summarizes the results of liquid junction solar cells prepared with polycrystalline and thin-film semiconductors [15]. As can be seen the efficiencies are fair. Thin films provide several advantages over bulk materials. Despite these possibilities, the actual efficiencies of solid-state polycrystalline thin-film PV solar cells exceed those obtained with electrochemical PV cells [22,23]. 

Based on our observations, we have reason to believe that single crystal performance will be approached in future thin film, polycrystalline semiconductor based solar cells with grain boundary recombination velocities reduced by strongly chemisorbed species. 

The first report of a CuInSe2/CdS heteroj unction solar cell-based on single-crystal CulnSe2-appeared in 1974 [72]. The cell achieved an efficiency of 5%. In 1983 the first electrochemical approach to produce a polycrystalline thin film of CuInSe2 was reported by Bhattacharya [73] in which Cu, In, and Se were deposited simultaneously from an acidic solution. Other approaches to the synthesis of polycrystalline CuIn(S,Se)2 thin films appeared quickly after the first report for example, Hodes et al. annealed an electrodeposited Cu-In alloy [74], Kapur et al. annealed stacked Cu-In layers [75], and Bhattacharya et al. annealed In-Se Cu-Se stacks [28]. The EDA routes which currently produce the most efHcient CuIn(S,Se)2 solar cells involve co-deposition of all of the constituent elements [76] followed by annealing in a sulfur atmosphere, and the electrodeposition of a Cu-In alloy with a small amount of Se, again followed by annealing in sulfur [34]. Both routes produce devices with around 11% power conversion efficiency. 

The electrochemical and photoelectrochemical properties of semiconductors in contact with electrolytes have been widely studied using single-crystal samples as well as polycrystalline thin films, and several excellent general books are available in the Uterature [135-138]. By contrast, the scope of this section is relatively narrow since it focuses specifically on practical appUcations of electrolyte contacts for the purpose of characterizing thin-fihn solar cell layers and partially completed PV devices of various kinds. 

Figure 2.79 Output power characteristic of a solid-state photovoltaic solar cell with polycrystalline thin-film CulnS2 for a chemical etching and an electrochemical process as indicated illumination, solar simulation AM 2, / = 50mWcm . ...

Electrodeposition of copper indium disulfide (CulnS2) has been reported [180-182], In a typical instance, single-phase polycrystalline CuInS2 thin films composed of 1-3 fim sized crystallites were grown on Ti by sulfurization of Cu-ln precursors prepared by sequentially electrodeposited Cu and In layers [183]. In this work, solar cells were fabricated by electrodepositing ZnSe on CuInS2. Cyclic... 

The optical properties of electrodeposited, polycrystalline CdTe have been found to be similar to those of single-crystal CdTe [257]. In 1982, Fulop et al. [258] reported the development of metal junction solar cells of high efficiency using thin film (4 p,m) n-type CdTe as absorber, electrodeposited from a typical acidic aqueous solution on metallic substrate (Cu, steel, Ni) and annealed in air at 300 °C. The cells were constructed using a Schottky barrier rectifying junction at the front surface (vacuum-deposited Au, Ni) and a (electrodeposited) Cd ohmic contact at the back. Passivation of the top surface (treatment with KOH and hydrazine) was seen to improve the photovoltaic properties of the rectifying junction. The best fabricated cell comprised an efficiency of 8.6% (AMI), open-circuit voltage of 0.723 V, short-circuit current of 18.7 mA cm, and a fill factor of 0.64. 

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