Date of Award

August 2018

Degree Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Physics

Advisor(s)

Eric A. Schiff

Second Advisor

Mathew Maye

Keywords

dispersion, MAPbI3, mobility, perovskite, solar cell, time-of-flight

Subject Categories

Physical Sciences and Mathematics

Abstract

Perovskite solar cells (PSCs) have impacted the photovoltaic industry over the past decade with unprecedented boosts in photo-conversion efficiencies. Perovskites’ dramatic rise has been due to borrowed ideas and research from other types of solar cell geometries. The initial surge in perovskite research started in 2009 with the discovery of unusually long photocharge carrier lifetimes and ambipolar diffusion. These discoveries changed the geometry of the solar cell from a dye-sensitized structure to n-i-p. The work done in this dissertation focuses on thin film methyl-ammonium lead iodide perovskites in n-i-p structures made by the National Renewable Energy Laboratory and Iowa State University. The initial goal of this research was to use photo carrier time-of-flight measurements to determine the drift mobilities of electrons and holes in the perovskite methylammonium lead iodide. I found evidence of dispersive transport for both photocharge carriers. I have made transient temperature-dependent studies of the drift mobility and the dispersion parameter, under otherwise normal device operating conditions. The low values of the electron and hole drift mobilities, ~10-1 cm2/Vs, under operating conditions suggest that the optimal thickness of the perovskite layer can be determined via calculation. The dispersive nature of perovskite thin films makes such calculations complicated. I propose, based on the temperature dependent studies of my work, that photocharge transport in perovskite thin films is spatially dispersive.

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