Executive Summary : | Typical chiral organic molecules/crystals show poor semiconducting properties because of the poor charge transport. In contrast, many inorganic crystals show good charge transport but do not show chirality. The broad idea behind the proposed work is to combine chirality and charge transport properties by using organic-inorganic hybrid metal halide perovskites like (R- or S-α-MBA)₂PbI₄ (MBA: Methylbenzylammonium). Chirality can induce (i) optical properties like circular dichroism and circularly polarized luminescence, (ii) structural asymmetry leading ferroelectricity and non-linear optical properties, and (iii) optoelectronic properties like bulk photovoltaic effect, circularly polarized photodetector, and spin-polarised light emitting diode. All these properties mainly originate from the valance and conduction band of chiral hybrid perovskites, and those bands are constituted by the orbitals of the inorganic (for example Pb-I) sublattice. The inorganic sublattice in general is achiral. So the above mentioned properties are observed only if the organic sublattice induces enough chirality in the inorganic sublattice. The chiral hybrid perovskite was first reported in the year of 2017 and the field is still very much in its infancy. The performances of chiroptic and chiral-optoelectronic properties mentioned above need to be improved by few orders of magnitude, before the chiral perovskites can be considered for future applications. The only way to improve the performance is by enhancing the chirality transfer from the organic to inorganic sublattice. Now what is the mechanism of this chirality transfer from organic to inorganic sublattice? The absence of a satisfactory answer to this question is a big knowledge-gap that exist today. The proposed work will focus on understanding the chirality transfer mechanism, which is critical for the rational design of novel chiral hybrid perovskites with improved performance. Centimetre-sized single crystals of a series (around 30 compositions) of chiral perovskites will be prepared, along with their thin films. Single crystal XRD, circular dichroism, second harmonic generation, and ferroelectricity will be used to understand the nature of hydrogen bonding and other non-covalent interactions between the organic and inorganic sublattice. A composition-structure-chirality correlation will be developed, based on which 2-3 champion chiral perovskite samples will be prepared. Wavelength and polarization dependent photodetector studies will be carried out to explore the potential of these chiral perovskites for bulk photovoltaic effect and circularly polarized photodetector. |