Growth and morphology of electrodeposited semiconducting films

Abstract

408F. Decker et al.: Growth and Morphology of Electrodeposited Semiconducting Films ductor caused by the metal islands are very narrow and the energy of charge carriers (electrons or holes) may be quantized, making the effect of the band modulation further insignificant. More details of the theory will be reported in the near future.It was mentioned in the preceding section that the V, for the Pt-coated and alkali-etched n-Si electrode is considerably higher than that of the normal p-n junction Si solid solar cell, though the barrier height (4B) for the latter should also take the value (EJe) at its maximum. Theoretically, V, is increased not only by the increase in c $~ but also by the decrease in the dark saturation current arising mainly from the diffusion of the conduction-band electrons to the surface in the case of a high-quality, n-type semiconductor electrode [18]. In the Pt-coated and alkali-etched n-Si electrode, the naked parts of the n-Si surface should be convered with a silicon oxide (SiO,) layer, as mentioned before. Since only very low densities of interfacial states were reported [19] to be present at the Si-SiO, interface, we can assume that the charge carrier recombination is negligible at the Si -SiO, interface. If the metal islands occupy a small portion of the whole n-Si surface, it therefore follows that the dark saturation current in the present electrode becomes very small and the V, becomes very high. For the p+-n junction Si solar cells, on the contrary, charge carrier recombination occurs in the p+-Si layer and also in the p+-Sifmetal (or conductive oxide) interface. This makes the dark saturation current higher than the above case.In conclusion, we have discovered that a semiconductor electrode coated with sparsely scattered, minute metal islands can generate a steady photocurrent and a very high V,,, considerably higher than that of a normal p-n junction solid solar cell, due to the generation of the high effective barrier height ($B) and the low dark saturation current. The eIectrodes of the present type also have the following advantages, which are expected generally for the Schottky-type solar cells [lS]: (1) High photocurrent output and good spectral response due to the presence of high electrial field near the semiconductor surface, (2) Elimination of energy consuming p-n junction processing, and (3) adaptability to polycrystalline or amorphous thin film solar cells. These features make the electrode of the present type a new promising candidate for highly efficient solar cells.The authors express their thanks to Akashi-Seisakusho Ltd. for kindly taking scanning electron micrographs of Pt-coated n-Si electrodes and to Shin-Etsu Handotai Co. for offering single crystal n-Si wafers. M. Vanzi*)PNUD BRA 82/032 -UIT, CPqD-Telebris, Campinas, SP, Brasil Electrodeposition f Electron Microscopy 1 Nucleation f SemiconductorsSemiconducting CdSe films have been electrodeposited on a variety of substrates by means of two techniques. The processes of nucleation, coalescence and growth have b...

ZnS , CdS , and Zn1 − x Cd x S Thin Films Deposited by the Successive Ionic Layer Adsorption and Reaction Process

“…Polycrystalline S I L A R CdS films are qualitatively m u c h better than other CdS films obtained by electrodeposition (88)(89)(90)(91)(92)(93)(94) or by chemical bath deposition (95)(96)(97)(98)(99) as far as their structure, morphology, stoichiometry, purity, and mechanical stresses are concerned. The latter are either amorphous or polymorphic, nonstoichiometric, and impurified by CdO, solvent inclusions, and chlorine.…”

Electrodeposition of CdTe thin films on Te-modified polycrystalline gold substrates

“…The stability constant (log K f ) of the Cd 2+ -NTA complex is 9.5 [14]. This initial study was followed by several other studies both by the same group and by other researchers, involving also, in some cases, semiconductor alloys containing CdSe [18][19][20][21][22][23]. To the best of our knowledge, we are not aware of previous instances of the use of complexing agents in the Cd-Te electrodeposition system.…”

“…There are several examples for the use of complexing agents in the semiconductor (CdSe) electrodeposition literature [15][16][17][18][19][20][21][22][23]. Thus, EDTA was used in early attempts to grow stoichiometric CdSe films by cathodic electrodeposition [15,16].…”

Electrodeposition of CdSe Films: In-Situ Study by Spectroscopic Ellipsometry

“…Among the various film preparation methods [1], electrodeposition is particularly promising [2]. CdSe films (typically 1Ϫ3 µm thick) made by cathodic electrodeposition on titanium from an aqueous solution containing selenosulfite and cadmium nitrilotriacetate [3,4] are quite uniform and smooth [2,5,6]. Their optical properties are of interest in the context of photoelectrochemical energy conversion.…”