PhD - Genk | More than two weeks ago
How perovskite solar cells behave under working condition: Logical Perovskite engineering for highly stable working device.
Despite the easy and economical fabrication process and remarkable achievements trend in perovskite solar cells (PSCs), presently perovskite material is suffering sever degradation and lacking the long-term stability, which acts as barriers for its commercialization. Rapid decomposition of PSCs was found when exposed to prolonged humidity, heat, light, oxygen, etc. For instance, on account of the hydrophilic properties of perovskite, moisture can easily ingress and degrade the perovskite material which eventually generate excess PbI2 that will act as source of recombination. During light illumination the instabilities results from the week hydrogen bonding between organic cation and inorganic Pb-I frame work. Light exposure can break relatively weak bonds in either the perovskite or the commonly used contact layers, thereby generate halogen vacancy-halogen interstitial pairs that enable halogens to migrate, or convert any oxygen that might be present to highly reactive superoxide. These external factors such as high temperature or UV illumination can also contribute to the generation of vacancies in perovskite layer because the volatile component such as methylammonium (MA) leaves/migrates from the active layer and results in deterioration of crystal structure.
Till date, much scientific work had been done to improve the stability of perovskite photovoltaic, the operational stability of PSCs is far away from the silicon competitor in the photovoltaic market. What’s worse, researchers usually evaluated the stability of perovskite PV devices by storing them in a controlled environment and intermittently testing their efficiency. Unfortunately, the storage stability of the devices is not suitable for assessing the actual reason for material’s degradation during working condition as well as the longevity of operational device. During continuous operational process various factors such as (i) thermal effect (illumination/current), (ii) interfacial electric field and (iii) generation of excess charge carriers involved in PSCs degradation. Although extensive research has been carried out on instability of perovskite material however, during working condition the influence of various factors from external environment on mechanism of perovskite degradation in a device are not well explored.
In this project, we aim to improve the long-term operational stability of PSCs. As one of the pioneers in the development of thin-film organic solar cells, Thin-Film PV team at imec has state of the art facilities for testing operational device stabilities. In a broader sense, the PhD candidate in this project need to explore the operational stability of perovskite solar cells. Specifically, considering different environmental conditions, during operational state, various governing mechanisms in a device such as; (i) defect state dynamics, (ii) carrier loss mechanism, (iii) and interfacial physics of perovskite material will be explored. During continuous operation of PSCs, the influence of different environmental conditions on the stability of perovskite material is expounded and a possible solution that can effectively improve the operation stability of working device, will be explored.
The current project aims for the development of highly stable and efficient material composition by employing different routes like passivation engineering, interface engineering or composition engineering. This project involves the basic understanding of mechanism behind perovskite film formation and physics of defects as well as fabrication processes of devices will be researched. By using a wide range of stability characterization techniques, such as MPP testing and continuous illumination testing, will create various learning pathways for the candidate.
Required background: Semiconductor physics, Material science, Engineering science
Type of work: 60% experimental, 30% characterization, 10% literature
Supervisor: Jef Poortmans
Co-supervisor: Tom Aernouts
Daily advisor: Yinghuan Kuang
The reference code for this position is 2021-128. Mention this reference code on your application form.