Document Type

Thesis - Open Access

Award Date

2021

Degree Name

Doctor of Philosophy (PhD)

Department

Electrical Engineering and Computer Science

First Advisor

Yue Zhou

Keywords

lower trap, defect passivation, interface modification, Low-bandgap perovskite solar cell, PEAI salt, PTAA modification

Abstract

Lead (Pb) -Tin (Sn) mixed perovskites suffer from large open-circuit voltage (VOC) loss due to the rapid crystallization of perovskite film, creating Sn and Pb vacancies. Such vacancies act as defect sites expediting charge carrier recombination, thus hampering the charge carrier dynamics and optoelectronic properties of perovskite films. In the first project, we focused on the passivation of perovskite surface defects to increase the opencircuit voltage of the 1.25 eV low-bandgap perovskite solar cells by utilizing a trace amount of Phenethylammonium iodide (PEAI) in the perovskite precursor solution as a doping agent. The incorporation of PEAI in perovskite precursors improved the perovskite film quality and crystallinity. In addition, it lowered the electronic disorder, enhancing opencircuit voltage up to 0.85 V, and power conversion efficiency up to 17.33 % was obtained with improved dark and ambient stabilities. In the second project, we improved the charge transport dynamics of the Pb-Sn perovskite using interface engineering strategy by inserting an ultra-thin layer poly [bis(4- phenyl)(2,4,6-trimethylphenyl)amine] (PTAA) over the commonly used HSL of poly(3,4 ethylenedioxythiophene)polystyrenesulfonicacid (PEDOT: PSS). Modification of HSL ensured the suppression of the interfacial defects, enlarged the perovskite grain sizes, improved the crystallinity of the perovskite layer, enhancing open-circuit voltage up to 0.85 V, and a fill factor approached to ~ 80 % thus, power conversion efficiency boosted up to 19.41 % with improved dark-shelf and operational stabilities. These simple yet powerful additives and interface engineering techniques seem promising strategies to mitigate VOC-loss in Pb-Sn mixed low-bandgap perovskite solar cells and can be easily applied in other mid-bandgap wide-bandgap perovskites.

Number of Pages

127

Publisher

South Dakota State University

Available for download on Thursday, December 15, 2022

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Rights Statement

In Copyright