Research Projects

Chiral hybrid perovskites are an emergent class of materials that integrate molecular chirality with tunable optoelectronic properties, unlocking physical phenomena including spin-orbit coupling, charge carrier asymmetry, ferroelectricity, and chiroptical responses such as circular dichroism (CD) and circularly polarized luminescence (CPL). Although lead-based chiral perovskites have shown pronounced chiroptical signatures, their toxicity and environmental instability limit practical applications. In this context, halide double perovskites (HDPs) and their hybrid analogues have emerged as promising alternatives due to their lead-free composition, superior stability, and structural versatility. However, the domain of chiral hybrid HDPs (CHDPs) remains underexplored, particularly in realizing ferroelectric and chiroptical functionalities, which require precise control over stereochemistry and crystallography. This proposal aims to engineer ferroelectric and chiroptical properties in low-dimensional (2D and 1D) CHDPs by modulating lattice distortions via systematic mixing of chiral and achiral cations. Low-dimensional halide perovskites attract interest due to greater structural diversity and stability than their 3D analogues. In the proposed study, dimensional confinement will be achieved by introducing bulky organic spacer cations at the A-site of A₂BB’X₆ HDPs, while chirality will be systematically imparted through controlled doping of chiral cations at the same site. These chiral cations are expected to induce lattice distortions, breaking inversion symmetry, a prerequisite for both ferroelectric and chiroptical activity. By rational mixing of chiral (4-Br-MBA⁺) and achiral (BA⁺ or TMA⁺) cations in 2D/1D HDPs, this proposal strategizes to modulate distortion and thus optimize chiroptical and ferroelectric properties. A comparative study of Bi³⁺ and In³⁺-based systems will probe the role of the Bi³⁺ 6s² lone pair in enhancing octahedral distortion and its influence on ferroelectric properties. To tune chiral emission energy, lanthanide (Ln³⁺) ions will be doped at Bi³⁺/In³⁺ sites to develop green-to-NIR emitting materials for effective use in spin-LEDs for broader opto-spintronic applications. Additionally, analysis of 2D and 1D CHDPs will elucidate the role of dimensionality in governing structure-property relationships. Notably, no comprehensive studies have yet demonstrated the coexistence of CPL and ferroelectricity in 2D/1D CHDPs, marking a critical gap in current research. The objective of this proposal is to deliver a class of multifunctional, non-toxic chiral materials with tunable CPL and ferroelectric functionalities, elucidating structure–property correlations and modulating chirality-induced octahedral tilting. This work will enrich the fundamental understanding of CHDPs and pave the way for their future application in CPL-based photodetectors, spin-optoelectronic devices, and non-volatile ferroelectric memory platforms.