Award Date

5-1-2019

Degree Type

Thesis

Degree Name

Master of Science in Engineering (MSE)

Department

Mechanical Engineering

First Committee Member

Shubhra Bansal

Second Committee Member

Thomas Hartmann

Third Committee Member

Hui Zhao

Fourth Committee Member

Clemens Heske

Number of Pages

170

Abstract

Third generation photovoltaics, including perovskites, are essential to improving solar technology for widespread future use. Perovskite solar cells have surpassed 23.7% power conversion efficiency, comparable to traditional silicon photovoltaic panels. However, these perovskites are fabricated using lead-based compounds, posing toxicity issues. Furthermore, existing perovskites have limited thermal and moisture stability in ambient environments. In order to address toxicity and stability concerns, as well as to maximize photon absorption in solar cells through bandgap optimization, this effort focuses on the development of novel leadfree perovskite materials. A cesium platinum iodide composition is selected as a model system due to the theoretical stability and oxidation resistance of platinum. CsPtI3 is expected to be metallic, however, 2D perovskite variant Cs2PtI6 offers promising properties of high absorption coefficient, with high carrier mobility and minority carrier lifetimes. Future work for this research includes demonstration of bandgap tunability with halide/chalcogen substitution for X anion, optimization of perovskite and charge transport layers, and exploration of Pt replacement with less expensive d-transition elements.

A solution-based process is used to fabricate thin-film samples with variables including solutes, solvents, and solution deposition techniques. Two types of cesium platinum iodide perovskite material have been synthesized with the platinum containing solute as primary process variant. Films prepared from platinum tetra-iodide and cesium iodide are majority Cs2PtI6 phase with a bandgap of around 1.4 eV and minority carrier lifetime ~ 2.7 microseconds. Films composed from platinum di-iodide and cesium iodide consistently have a bandgap of around 1.8-2.0 eV and minority carrier lifetime ~ 62 ns. Both material types also show high absorption coefficient. Devices fabricated from both material variations show definite diode behavior but no conclusive photo response and need further research. Detail on material synthesis, material characterization, film properties, device functionality, challenges, and commentary of the cost and future study of Cs2PtI6 and perovskite derived from the Cs2PtI6 model structure is provided.

Keywords

Lead free; Novel material; Perovskite; Solar device; Wide bandgap

Disciplines

Engineering Science and Materials | Materials Science and Engineering

Language

English


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