Date

2019

Department or Program

Physics

Additional Department or Program (if any)

Computer Science

Primary Wellesley Thesis Advisor

Rebecca Belisle

Additional Advisor(s)

Robbie Berg

Additional Advisor

James Battat

Additional Advisor

Ellen C. Hildreth

Abstract

Lead sulfide (PbS) quantum dot (QD) solar cells are emerging thin film solar cells that are solution processible at low temperatures, potentially on lightweight and flexible substrates at a low cost. Despite this prospect, PbS QD solar cells remain far from commercialization due to their low power conversion efficiency compared to other types of solar cell. This thesis explores the development of a novel surface passivation protocol to raise the open circuit voltage of PbS QD solar cells and thereby improve the power conversion efficiency. The protocol implements a novel solution phase ligand exchange method that involves two kinds of halide salts. The impacts of these salts on PbS QD solar cell performance and optical properties are studied through a comparison of a control process---that involves only one kind of halide salt---to the proposed process---that utilizes dual halide treatment. Particularly, open circuit voltage is both experimentally measured and theoretically calculated to assess the potential of the proposed treatment. In both cases, devices made with the novel dual halide treatment show improved open circuit voltage compared to the devices made with the control process. This improvement presents the potential for multiple halide treatment in better surface passivation. Moreover, theoretical results being in good agreement with the observed results suggests the viability of theoretical performance analysis using optical measurements in surface passivation studies.

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