PHOTOELECTROCHEMICAL STUDY OF THIN-FILM SEMICONDUCTOR HETEROSTRUCTURES - JUNCTION FORMATION PROCESSES IN CDS-VERTICAL-BAR-CDTE SOLAR-CELLS

A photoelectrochemical study of SnO2/CdS/CdTe thin film heterostucture s in contact with an electrolyte has been carried out. Upon thermal an nealing treatment the isotype structure SnO2(n)/CdS(n)/CdTe(n) is conv erted into an n/n/p structure, due to type conversion of the CdTe laye r. This process is the basis of the formation of efficient CdS/CdTe so lar cells. In contact with the electrolyte a transistor-like n/n/p/n s tructure is formed. A theoretical analysis of the behaviour of this st ructure is presented. By changing the applied potential the relative c ontributions from the internal CdS/CdTe barrier and the outer CdTe/ele ctrolyte can be separated. The simulation of the spectral responses al lows one to determine the semiconducting properties of the semiconduct ors involved and those of the internal barrier. The improvement of the p-type CdTe properties caused by a CdCl2 surface treatment before ann ealing is confirmed by this method.