Understanding Grain Growth Mechanism in Vacuum Evaporated CdTe Thin Films by Different Halide Treatments: An Evolution of Ion Size Impact on Physical Properties for Solar Cell Applications

ABSTRACT

In the present study, detailed investigation on postdeposition halides treatment using CdCl₂, CdI₂, MgF₂, MgCl₂ and MgI₂ is undertaken over thermally evaporated CdTe films. As-deposited films are subjected to halide treatment and subsequent annealing at 385°C. Halide activation induced grain growth mechanism is presented along with anions and cations roles on change in films properties and formation of different complexes. XRD patterns of all CdTe thin films exhibited polycrystalline nature with preferential cubic phased (310) plane except for CdI₂ treated films where preferred reflection is appeared corresponding to (220) plane. Grain growth is observed with treatment employing amicable estimation tools. All films have a conspicuous ohmic character owing to linear I–V plots. Optical study reveals that CdCl₂ treated CdTe films have higher absorbance and optical energy band-gap is measured out in the range 1.42–1.53 eV with halide treatment. Surface topography and PL study revealed to variations in surface roughness and photoluminescence peaks intensity with halide treatments. Film growth and treatment are validated by EDS analysis and FESEM images demonstrated explicit grain growth. Findings warrant amazing role of halide activation on film properties and CdCl₂ is found a suitable surface treatment agent to CdTe films in order to develop better devices.

Graphical abstract

KEYWORDS:

• Thin films
• physical properties
• halide treatment
• grain growth
• solar cells

Acknowledgments

Authors are highly grateful to the Sceince and Engineering Rsearch Board (SERB), New Delhi for financial assistance through Extramural Research (EMR) project (vide No. EMR/2017/003330) and to the DST-FIST through Mohanlal Sukhadia University, Udaipur for AFM and XRD facilities. The Ministry of Education, Government of India and Ministry of Higher Education, Govt. of Rajasthan through RUSA 2.0 R & I projects are acknowledged for PL facility and recurring expenses. The Center of Excellence for Industrial Textiles, PSG College of Technology, Coimbatore is also accredited for FESEM and EDS facilities.

Disclosure statement

The authors declare that they are having not known any conflict of interest that could have existed to impact this work financially and personally .

Additional information

Funding

This work was supported by the Ministry of Education, Goverment of India and Ministry of Higher Education, Government of Rajasthan through (RUSA 2.0) Research and Innovation project; Science and Engineering Research Board, Deaprtment of Science and Technology, Government of India through Extramural Research project (EMR/2017/003330).