Degree Type

Dissertation

Date of Award

2019

Degree Name

Doctor of Philosophy

Department

Mechanical Engineering

Major

Mechanical Engineering

First Advisor

Ganesh Balasubramanian

Second Advisor

Duane D. Johnson

Abstract

Organic-inorganic halide perovskites have been on the radar of the photovoltaic community for a few years now. Significant research has been done on making the solar cell devices based on these materials more efficient. These perovskites have the following excellent photovoltaic properties : desirable band gap, high number of charge carriers, and high absorption coefficient. In this thesis, we aim to enhance these properties by using low-dimensional materials. We consider heterostructures of the organic-inorganic halide perovskites and characterize them for their thermo-electric properties. The heterostructures are constructed using the idea of low-dimensional structures.

In this work we engineer these structures with the desire to increase their thermal electric figure of merit. We use computational methods to evaluate these materials and compliment the results using experiments. The computations were done using first principle calculations and Boltzmann theory to calculate the electronic transport coefficients. Experimentally we also prepare these superlattice structures using sequential thermal deposition and consider them for their electrical transport. Using the optimized structures obtained from first principle calculations, we also simulate phonon dynamics to look at the thermal properties. The challenge is to find the right optimization to get the desired properties in these materials. The results give us motivation to test different superlattice architectures and establish an algorithm to tailor desired properties in these structures.

In chapter 5 we introduce a hybrid optimization algorithm and show its application in material sciences. Using the algorithm we obtain partially ordered structures of hybrid perovskite structures and finally do first principle calculations to calculate the energetics of hybrid structures.

The last two chapters propose some engineering strategies to increase the stability of halide perovskites while maintaining similar photovoltaic performance. The discussion is focused on designing interfaces between methylammonium lead iodide perovskite and various stable two dimensional materials. The effects of different interfaces is analyzed and their impact on performance is discussed through various thermoelectric properties. Finally, it is found that a heterogeneous interface between methylammonium lead iodide and boron nitride creates a much stable perovskite and at the same time maintains the performance.

Copyright Owner

Rahul Singh

Language

en

File Format

application/pdf

File Size

171 pages

Available for download on Friday, December 18, 2020

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