Thin Film Materials and Devices:

Development of thin film solar cell technologies has been given a big boost by the discovery of light absorbers with the nominal composition ABO3 (perovskites and perovskite-like materials). No other material has shown the kind of rapid progress in terms of efficiency improvements in a short period of time, so that it can become competitive with the dominant solar cell technologies. Also, the processing techniques to achieve these high efficiencies are simple, non-vacuum processes. Due to these reasons, this material class has become the research focus of many groups worldwide.

In Phase I of NCPRE, there were efforts underway to develop single junction cells based on perovskites, and efficiencies of 15% were achieved. With our capabilities in perovskites, CZTS, and Si-based single junction cells, the group is mainly focusing on integrating these efforts to realize cells in a tandem configuration, with the cell based on the perovskite absorber as the top layer and with CZTS and/or Si-based solar cells forming the bottom layer. In our foray into the realm of tandem devices, we are working to achieve > 15% efficient cells of dimensions upto 1 cm2. This would also require that CZTS based solar cells with efficiencies greater than 8% are obtained via a solution/ink-based technique, which is also one of our targets.

One major problem with the large-scale deployment in the future arises from the low stability of the specific perovskite that is currently utilized. So, the different aspects of our second activity will be focused on (a) developing protective layers that also serve the purpose of replacing the currently-used costly hole transport material, organic, inorganic, and carbon-based, as well as, (b) the development of perovskites that possess an inherent stability, e.g. oxides, oxynitrides, chalcogenides. The development of the new, lead-free, long stability perovskites, is amply supported by materials and device modelling activities.

The Thin Film Materials and Devices group is headed by Prof. Bala Kavaipatti.