CuGaSe 2 thin films prepared by a novel CCSVT technique for photovoltaic application

Abstract

A novel chemical close-spaced vapor transport (CCSVT) technique has been developed for the growth of the CuGaSe 2 (CGSe) thin films on areas as large as 10×10 cm 2. Cu precursors deposited on clean and Mo-coated soda lime glass substrates are thermally and chemically treated under gaseous GaCl x /H 2Se atmosphere in the CCSVT cell. The Ga 2Se 3 employed as source material is stoichiometrically volatilised at 550 °C by a controlled amount of HCl/H 2 agent. Single phase CGSe thin films are prepared with a growth rate of 230–240 nm/min by using a single stage process. A two-stage process is applied for the fine tuning of the CGSe composition and electronic properties appropriate for the subsequent solar cell preparation. Film characterisation including X-ray diffraction measurements, scanning electron microscopy observations, X-ray fluorescence analysis and elastic recoil detection analysis has been carried out. An 8.7% active area efficient ZnO/CdS/CuCaSe 2 solar cell under AM1.5 conditions has been achieved.