Abstract
In this work, the irreversible processes in light heating of Silicon (Si) and Germanium (Ge) thin films are examined. Each film is exposed to light irradiation with radiative and convective boundary conditions. Heat, electron and hole transport and generation-recombination processes of electron-hole pairs are studied in terms of a phenomenological model obtained from basic principles of irreversible thermodynamics. We present an analysis of the contributions to the entropy production in the stationary state due to the dissipative effects associated with electron and hole transport, generation-recombination of electron-hole pairs as well as heat transport. The most significant contribution to the entropy production comes from the interaction of light with the medium in both Si and Ge. This interaction includes two processes, namely, the generation of electron-hole pairs and the transferring of energy from the absorbed light to the lattice. In Si the following contribution in magnitude comes from the heat transport. In Ge all the remaining contributions to entropy production have nearly the same order of magnitude. The results are compared and explained addressing the differences in the magnitude of the thermodynamic forces, Onsager’s coefficients and transport properties of Si and Ge.
Highlights
The study of transport phenomena and irreversible processes is necessary in the development of many technological devices
We address the problem of light heating of Si and Ge thin films and study in detail the contributions to the entropy production in the system
We find an analytical solution of Equation (3) for the stationary state, obtained with Wolfram Mathematica 10.0, where the source term is taken from Equations (B1)
Summary
The study of transport phenomena and irreversible processes is necessary in the development of many technological devices. Multilayer systems are involved, for instance, in the development of new type of coats which have application as glues, filters, among others, as well as in thermoelectrics, optoelectronics, solar cells, thermal barriers, mirrors, etc. The minimum entropy production principle states that a system evolves in time reaching a minimum entropy production rate at the stationary state This often establishes a relation between irreversible processes and optimal performance [5,6]. The investigation of these relationships in dielectric thin films constitutes the foundation of the understanding of behavior and performance of multilayer systems. This theme has attracted the interest of the scientific community [7,8,9,10] and it is the one we are interested in
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