Thermally Evaporated MoOx and TaTm as Hole Transport Layers for Perovskite Solar Cells

Towards fully thermally evaporated perovskite solar cells

Master thesis (2024)

Authors

J.D. Apawti Electrical Engineering, Mathematics and Computer Science

Contributors

L. Mazzarella Photovoltaic Materials and Devices - EEMCS (mentor)
J. Yan Photovoltaic Materials and Devices - EEMCS (mentor)
P.A. Procel Moya Photovoltaic Materials and Devices - EEMCS (mentor)
O. Isabella Photovoltaic Materials and Devices - EEMCS (graduation committee member)
F.C. Grozema ChemE/Opto-electronic Materials - AS (graduation committee member)
Faculty
Electrical Engineering, Mathematics and Computer Science
More Info
expand_more

Published Date

09-09-2024

Language

English

Reuse Rights

Other than for strictly personal use, it is not permitted to download, forward or distribute the text or part of it, without the consent of the author(s) and/or copyright holder(s), unless the work is under an open content license such as Creative Commons.

Faculty

Electrical Engineering, Mathematics and Computer Science

Abstract

As global temperatures rise and energy demands increase, the need for clean, renewable
energy sources is more critical than ever. Solar energy is one of the key solutions, with the
majority of solar panels currently on the market being made from crystalline silicon. However, emerging photovoltaic (PV) technologies such as perovskite solar cells have already demonstrated efficiencies comparable to those of silicon solar cells, making them a promising contender to achieve even higher efficiencies.

Most of the layers in perovskite solar cells are deposited via spincoating, which is a fast and easy process but can only be done on laboratory-scale. However, deposition through thermal evaporation offers significant advantages, enabling fabrication of nanometer-thin films and facilitating large-scale fabrication needed for future industrialization of perovskite solar cell. Therefore, this research aims to develop perovskite solar cells entirely through thermal evaporation.

The reported number of hole transport materials deposited through thermal evaporation is limited. Recently, fully thermally evaporated perovskite solar cells have been created using the hole transport materials MoOx and TaTm, and these hole transport materials will be studies in this thesis.

The MoOx and TaTm were used as single and double hole transport layer to replace the
reference layer of spincoated PTAA. It was found that the MoOx in direct contact with the pervovskite resulted in a chemical reaction, which negatively affected the energy alignment. The MoOx also showed poor charge carrier selectivity, resulting in high interfacial recombination. Great hole extraction from the perovskite was observed for TaTm, however, a misalignment of the band energy with the electrode hindered the hole collection. Improved hole transfer was found with MoOx and TaTm being used a double hole transport layer. Here, the TaTm functions as a passivation layer between the MoOx and perovskite, while effectively blocking the electrons. In turn, the MoOx improved the energy alignment from the TaTm to the electrode to improve the hole collection.

A thickness optimization of the hole transport layers was also performed. For MoOx as
single hole transport layer, it was found that number of oxygen vacancies decreased with
thickness, leading to less recombination. No change was observed for TaTm as single hole
transport layer when varying the thickness. However, as a double hole transport layer with MoOx, increasing the thickness of TaTm led to an increase in Voc . Ultimately, a thin layer of 2 nm MoOx with a 5-nm thick TaTm showed the most promising results, demonstrating a final efficiency of 4.73%.