Determination of carrier lifetime in thermally evaporated In2S3 thin films by light induced transient grating technique

S Rasool,V Grivickas,M S Tivanov,K T Ramakrishna Reddy,K Saritha,P Ščajev,I Svito

doi:10.1007/s00339-020-03495-5

Abstract

In2S3 thin films were deposited onto soda lime glass substrates using thermal evaporation technique at a constant substrate temperature of 300 °C and the films were annealed in a sulfur ambient at 250 °C and 300 °C for 1 h. Light induced transient grating (LITG) technique was used to determine the carrier lifetime in In2S3 thin films. The determined carrier lifetime values for different excitation energy densities, I0 = 0.06–1.64 mJ/cm2 decreased from 206 to 18 ps and 150 to 14 ps for the films annealed at 250 °C and 300 °C respectively. Further, the bimolecular, Auger recombination coefficients and diffusion coefficient were determined in the films. The observed bimolecular carrier recombination origin was explained by interface and Auger recombination processes.

Highlights

Cu(In,Ga)Se2 (CIGSe) and CdTe-based solar cells have reached high conversion efficiencies of 22.6% and 22.1% using CdS as a buffer layer [1, 2] and are currently commercialized
The determined carrier lifetime values for different excitation energy densities, I0 = 0.06–1.64 mJ/cm2 decreased from 206 to 18 ps and 150 to 14 ps for the films annealed at 250 °C and 300 °C respectively
The decrease in carrier lifetime with increase of excitation energy density might be due to bimolecular, Auger or surface/interface recombination processes that occur in these films

Summary

Introduction

Cu(In,Ga)Se2 (CIGSe) and CdTe-based solar cells have reached high conversion efficiencies of 22.6% and 22.1% using CdS as a buffer layer [1, 2] and are currently commercialized. The large scale production of these solar cells using CdS is environmentally unsafe to handle because of the toxicity of cadmium. Alternate materials are of much interest that can successfully replace CdS. In this context, In2S3 is a potential alternative material, because of its wide energy band gap (2.0–3.3 eV), n-type conductivity, non-toxic and photoconductive nature [3,4,5,6]. Spiering et al [7] reported a record solar cell efficiency of 18.2% using evaporated In2S3 thin film as a buffer layer for Cu(In,Ga)Se2-based thin film solar cells

Experimental

Results and discussion

Conclusion