7 - Fabrication and Properties of Window Layers For Thin Film Solar Cells

Abstract

The chapter discusses the fabrication of different n -type window or buffer layers, such as CdS, zinc sulfide (ZnS), indium sulfide (InS), and so on, and their surface, structural, optical, and electrical properties. In addition, the preparation and characteristics of transparent n -type conducting layers, such as zinc oxide (ZnO), ITO, and FTO layers are described for CIGS thin film solar cell applications. The n -CdS thin films are extensively employed as window layers with many p -type absorbers, such as Cu 2 S, CdTe, InP, and CuInGaSe 2 in the thin film solar cells. The CdS layers have been prepared by several techniques, such as spray, CBD, sputtering, vacuum evaporation, MOCVD, e-beam, and so on. The CdS thin films are also formed by simple and cheap spray pyrolysis technique for thin film solar cell applications. Thickness of the films can be calculated from spectral transmittance curve if multiple interference maxima and minima exit. The band gap of semiconductor increases with increasing doping concentration ( n e ) because the electrons occupy the lowest states in the conduction band in the form of electron gas for n-type. The band gap broadening can be achieved using the Burstein-Moss shift relation. The InS is one of the nontoxic friendly buffer layers for thin film solar cells, which consists of different structures.