THIN FILM LABORATORY

kinetic roughening in thin films

Recent developments in scaling invariance and universality have led to a growing interest in kinetic roughening theory with special attention being paid to studies on roughness evolution in thin films grown under far-from-equilibrium conditions.The study of evolving surfaces provides insight to the fundamental growth dynamics and enables one to control the roughness of the films. Such a study is of high technological relevance in that roughness of thin films in multilayer structures affects electrical, optical, mechanical and catalytic properties, and hence, determines the eventual performance of devices.

Scientific Reports, 6, 33136 (2016) EPL (Europhysics Lett.) 96 (2011) 26003.J. Appl. Phys. 106 (2009) 054908

Inorganic thin film solar cells from earth-abundant elements

In recent years, kesterite Cu₂ZnSnS₄ (CZTS) has emerged as a leading sustainable absorber layer, alternate to the more popular Cu(InGa)(SSe)₂ (CIGSSe). The intensified research on CZTS has culminated in progress of photo-conversion efficiency (PCE) from ~6.8 in 2008 to beyond 12% just in a few years. Compared to the more mature CIGSSe technology, however, synthesis of CZTS has required more customized approaches due to its peculiarities. For example, the formation of the single phase, which is crucial to the performance to the photovoltaic devices, has been found to be a big challenge in CZTS, especially compared to CIGS, since a single phase exists within a much smaller chemical potential window. The tendency to form binary phases, selective re-evaporation of elements from the film, reaction at contacts, etc. further make it difficult to control the intended composition and the formation of single phase. Our group aims at fabricating cost-competitive devices on various deposition techniques including single target sputtering and non-toxic solution based approaches.

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