Development Organic Back Contact for Thin-Film CdS/CdTe Solar Cell

Abstract

Hybrid solar cells on the basis of CdTe photoabsorber layer and CdS buffer layer on glass/ITO substrate in combination with organic back contact layer of highly conductive polymer poly(3,4-ethylenedioxythiophene) (PEDOT) doped with polystyrenesulfonate (PSS) were prepared using vacuum evaporation and spin-casting techniques. In order to prepare the complete solar cells, the appropriate deposition parameters and thickness of highly conductive PEDOT-PSS layers were selected experimentally. The best result was obtained by spin-coating of PEDOT-PSS aqueous dispersion which was mixed with glycerin, N-methyl-2-pyrrolidone (NMP), isopropanol and tetraethoxysilane for the enhancement of electrical conductivity of deposited PEDOT-PSS films. It was found that prepared conductive polymer film gives good ohmic back contact to the surface of p-CdTe semiconductor film in complete solar cell. For a current contact preparation to PEDOT-PSS layer, the silver suspension deposition and gold evaporation techniques were applied separately. The best obtained structure glass/ITO/CdS/CdTe/PEDOT-PSS/Ag showed so far an open-circuit voltage of around 560 mV and a short-circuit current density of around 12 mA/cm2 under white light illumination with an intensity of 100 mW/cm2.