Research Projects

The above-bandgap photovoltages in non-centrosymmetric materials upon uniform illumination has opened up opportunities in ferroelectric photovoltaics. The polarization arising due to crystal asymmetry in these materials induces a photocurrent by separating the photo-generated electron-hole pairs, unlike the conventional semiconductor junction based devices. In addition to the polarization, charge separation can also be achieved by the Schottky barriers at the ferroelectric/metal interfaces and/or by the ferroelectric domain walls. Thus, the mechanism of photovoltaic charge transport can be complex, especially in thin films and has not yet been established in literature. On the other hand, the conventional perovskite oxides of the form ABO3, which exhibit high polarization, have poor photovoltaic performance because of their wide band gap that allows absorption of only a very limited portion of visible radiation. In this context, theoretical studies have predicted CaZrS3 (CZS) with a tunable direct band gap of 1.9 eV to be a very potential absorber material. However, there is no reports of fabrication CZS thin films experimentally. In addition, these class of materials can exist in multiple structures, which can directly affect the polarization and hence, the photocurrent. Thus, it is of interest to synthesis the CZS thin films and investigate the photovoltaic charge transport in these thin films not only from fundamental but also from application point of view. Furthermore, this proposal aims at a detailed study of bandgap engineering in CZS thin films by manipulating the B-site cations in the form of partial Ti substitution. We propose to synthesize Ti-modified CZS thin films via sputtering and elucidate the process parameter dependence of composition, phase evolution, optical and electrical properties and photovoltaic charge transport in the films. The outcome of the proposal is expected to reveal the competing mechanisms of photovoltaic charge transport in the thin films and spur development of new class of photovoltaics.

Photoferroics, Chalcogenides, perovskites, Thin films, Photovoltaics