Deposition of CdS Thin Film by Thermal Evaporation

Abstract

The CdS thin film is widely used for numerous applications such as in optoelectronic devices, solar cells, LEDs, photonics devices etc. The ultra-thin CdS layer is commonly used as by layer or as window layer for CdTe, CIS, CIGS, CZTS thin-film solar cells. The CdS has high bandgap of 2.42 eV and transparent after 510 nm wavelength. The excellent optoelectronics properties of CdS material are very attractive as hetero-junction partner (n-type) in thin-film solar cells. There are several fabrication techniques used to deposit thin CdS layer such as Screen Printing, Thermal Evaporation (TE), Molecular Beam Epitaxy (MBE), Chemical Vapour Deposition (CVD), Pulsed Laser Deposition (PLD), Sol-Gel, Spray Pyrolysis, Electrochemical Deposition, Close Space Sublimation (CSS), Sputtering, Chemical Bath Deposition (CBD) etc. Among them TE is low cost, faster and the complete set-up is ready to be used in the Lab. In this work, the CdS thin films were grown on borosilicate glass substrate by thermal evaporation techniques using VCM 600 V1 in a high vacuum condition at room temperature. Around 200nm CdS thin film were fabricated on BSG substrate and it took 35 minutes only. As grown CdS thin film were characterized to evaluate its properties for the possible application in CdS/CdTe thin-film solar cell. The as-deposited CdS film characterization results showed lower resistivity with higher mobility and carrier concentration which are good enough to be used in thin-film solar cells, LEDs and photonic devices.