Crafting Self-Powered Photodetectors with Low Dimensional Hybrid Halide Double Perovskite

Mishra, Jharana (2025) Crafting Self-Powered Photodetectors with Low Dimensional Hybrid Halide Double Perovskite. Masters thesis, Indian Institute of Science Education and Research Kolkata.

Text (MS Dissertation of Jharana Mishra (23MP004)) 23MP004_Thesis_file.pdf - Submitted Version Restricted to Repository staff only Download (6MB)

Abstract

In today's era of advanced technology, the demand for energy from various devices has surged dramatically. Consequently, the exploration of alternative and environmentally sustainable energy sources has become a central focus within the scientific community. Among these alternatives, photovoltaic cells have long captured the attention of researchers, with perovskite photovoltaic cells emerging as a rapidly growing field. Lead halide perovskites, with the general formula ABX3 (where A = Cs+, Rb+, B = Pb2+, Sn2+ and X = Cl, Br, I), have become widely used materials for photovoltaics due to their exceptional efficiency. However, the inherent toxicity of lead has raised concerns, prompting researchers to explore alternative materials. One promising alternative is layered double halide perovskites, with the formula A2MIMIII X6, where MI is a monovalent metal cation, MIII is a trivalent metal cation, and X = Cl, Br, or I. These materials have emerged as a viable and environmentally friendly option for photovoltaic research. While much of the existing literature focuses on the use of expensive late transition metals, this research work explores the potential of more abundant Group-I and Group-XV metals. It also investigates the use of different spacer cations, such as hexamethylenediamine (6N6) and para-phenylenediamine (PPA), as well as a variety of halides. The aim is to develop inexpensive, tunable band-gap materials for photovoltaic research. The initial phase of this research focuses on the synthesis of perovskite single crystals using the Solution Temperature Lowering method. This process yields the following compounds: (PPA)₂NaBiIx (PNBI), (PPA)₂NaBiBrx (PNBB), (6N6)NaBiIx (HNBI), and (6N6)NaBiBrx (HNBB). Single crystal measurements, along with thorough characterization, revealed a layered structure with an average band gap of 2.54 eV and thermal stability up to 280°C. However, some studies have indicated that the sodium content in certain structures is unexpectedly low, and the reasons behind this are still under investigation. Next, an out-of-phase photodetector was fabricated using a series of processes. The device architecture is described as FTO-cTiO₂-Perovskite Layer-Au. Device performance was then measured, among the four synthesized phases, the one-dimensional HNBB phase exhibited the best photodetector performance, with a maximum responsivity of 6.9 A/W at 2.6 V, a peak detectivity of 53.2 × 108 Jones at 1 V, and the highest carrier mobility of 6 × 10-4 cm²/V.s. Devices exhibit notable photoresponse even without external bias or under very low applied voltage, indicating self-powered operation.

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