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Strain Modulation of Properties of Inorganic Halide Perovskite (CsPbBr3) : A DFT study


Halide perovskites have quickly risen in the ranks of 3rd generation photovoltaic technologies over the past decade and have been a subject of intense experimental and computational study. This class of materials has been shown to have excellent optoelectronic properties such as large absorption coefficient, long carrier diffusion length and high carrier mobility but has poor stability. Several strategies such as elemental doping, morphology control and surface passivation have achieved incredible success in increasing both performance and stability of perovskite solar cells. The certified power conversion efficiency of perovskite solar cells has exceeded 24 % with efficiency > 18 % now being reported regularly.

However, problems such as phase segregation, limited dopant solubility and high cost of processing are associated with these techniques. Strain modulation has been proposed as a promising technique to improve performance but no comprehensive study on the effect of strain on perovskite exists. The work in this thesis is motivated by this gap of knowledge and aims to evaluate strain modulation as a tool for improving solar cell performance.

Chapter 1 provides a summary of the research progress made so far and establishes the motivation of this study. Chapter 2, provides the details of all the computational techniques/methods used in this study. Chapter 3, 4 and 5 discusses the results obtained for strain modulation of optoelectronic properties, ion migration barrier and vacancy defect formation energy respectively. Based on these results it is proposed that the unstrained perovskite layer will yield better performance due to its lower band gap, lower effective carrier mass, higher ion migration barrier and higher vacancy defect formation energy when compared to the experimentally found tensile strained perovskite layer in the solar cells.

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