Developing highly stable halide perovskite for solar cells and photodetectors

Lead halide perovskite, 3D cubic AM(ll)X3, have garnered significant attention due to their exceptional optoelectronic properties, enabling applications in;solar cells, light-emitting diodes, and photodetector applications. However, concerns over lead toxicity and environmental pollution necessitate the;development of lead-free alternatives. All-inorganic (i) A3M(lll)2X9 2D-layered halide perovskite (2D-LHP), (ii) A2M(l)M(lll)X6 3D-cubic double halide;perovskite (3D-cDHP), and (iii) A4M(ll)M(lll)2X12 layered-double perovskite (LDHP) are emerging as promising materials due to their superior stability;under light, heat, and atmospheric conditions compared to organic-inorganic halide perovskites. However, their optical and electronic properties,;especially in relation to photovoltaic, light emitting and photodetector applications, require further exploration and optimization. This proposal focuses on;leveraging alloying and sublattice distortion in 3D-cDHP and LDHP as a strategy to tailor their optoelectronic properties. Specifically, we aim to;investigate the effects of substituting M(I) (Ag+, Na+, Cu+) and M(III) (Bi3+, Sb3+, ln3+) sites in the A2M(l)M(lll)X6 structure, and M(II) (Cu2+, Mn2+,;Cd2+) and M(III) (Sb3+, Bi3+) sites in A4M(ll)M(lll)2X12 structure with Cs+ and Rb+ as the preferred A-site cation, and Br- and I- as halide anions. This;approach capitalizes on the isoelectronic nature of these cations with Pb2+, allowing for structural stability while introducing unique optical and electrical;properties. Recent studies suggest that alloying in double perovskites induces local symmetry changes and distortions in the MX6 octahedra [1-3]. These;distortions, driven by Jahn-Teller effects, break inversion symmetry and deactivate parity-forbidden transitions, enabling enhanced excitonic;recombination. Furthermore, sublattice distortions reduce the optical bandgap, offering new opportunities for bandgap engineering. These changes are;expected to result in materials with improved light absorption and emission properties, making them highly suitable for photovoltaic and optoelectronic;devices. Our proposed research will focus on the following objectives: 1. We will synthesize alloyed double perovskites with compositions;(A2M(l)M(lll)X6 and A4M(ll)M(lll)2X12 ) using solution-based thin film methods, viz, spin coating process and thermal evaporation technique. Structural;characterization will involve X-ray diffraction, Raman spectroscopy and electron microscopy and spectroscopy techniques to confirm crystal phases and;identify local distortions. 2. We will employ UV-Vis spectroscopy, photoluminescence (PL), and time-resolved PL to study bandgap evolution and;excitonic behavior. Carrier mobility and conductivity will be analyzed using Hall effect measurements and impedance spectroscopy. 3. Optimized double;perovskites will be integrated into photovoltaic and photodetector devices. Device performance, including power conversion efficiency (PCE) and;external quantum efficiency (EQE), and photodetector performances will be evaluated under standard test conditions. By systematically exploring the;interplay between cationic alloying, sublattice distortion, and optoelectronic performance in cubic and layered double perovksite, this research aims to;establish design principles for next-generation lead-free perovskites. The resulting materials are expected to achieve higher efficiency and stability, and;sensitivity paving the way for sustainable and scalable applications in solar energy and sensing. In summary, this proposal seeks to address critical;challenges in double perovskite research by advancing our understanding of alloying-enabled sublattice distortions. The outcomes will contribute;significantly to the development of environmentally friendly, high-performance optoelectronic devices.;