Modelling laser-induced heat transfer phenomena of thin-films using OpenFOAM

Abstract

• A Finite Volume (FV) Model for simulating laser annealing of thin-film based structure. • Experimental validation of the OpenFOAM-based conjugate heat transfer model. • Detailed understanding of the diode laser-induced thermal and optical phenomena of the multilayer structures. • A guideline for optimising and designing of thin-film based architecture. This paper presents a numerical simulation model for analysing diode laser-induced thermal phenomena on high absorbing thin-films. Continuous wave (CW) diode laser, in the form of millisecond annealing, is a promising tool for processing of the high absorbing thin-film based solar cells. The localised nature of laser processing, in one hand, gives an opportunity to heat the film to a higher temperature over a much shorter time than the conventional methods, while, on the other hand, allowing the substrate to remain at low temperature with a low ramp-up rate. Also, unlike the laser processing in pulse mode, the CW diode laser can heat the high absorbing thin-films over a longer period without initiating melting and dwetting. Since the CW diode laser-induced thermal treatment is entirely characterised by its parameters, the inappropriate setting of its parameters may lead to a negative effect on the absorber layer . In view of these, being highly a thermal process, the basic understating of the CW diode laser annealing of high absorbing thin-film is necessary, which arguably may not be possible using the experimental techniques. Numerical simulations, in this case, offer the possibility to acquire knowledge of the process; hence, in this contribution, a numerical model has been developed in an open-source based computational fluid dynamics (CFD) platform, known as OpenFOAM. Upon development of the model, its prediction has been compared with the experimental results of the CW diode laser annealing of silicon thin-film on the glass substrate , in which an excellent agreement with the experimental results has been observed. In the second part of this study, the developed numerical model has been implemented to reveal the CW diode laser-induced thermal phenomena of the high absorbing CZTS thin-films, which is considered as deposited on Molybdenum (Mo) coated glass substrate, a typical structure used for designing of CZTS thin-film based solar cells. Although CZTS thin-film is considered as the ideal material for using as an absorber in the next generation thin-film based solar cells, its behaviour in the case of CW diode laser-induced thermal treatment has not been understood yet. Hence, the present study may likely to contribute to the processing and optimising of the CZTS thin-film based structure.