Research of decomposition mechanism of mixed cation-anionic metal halide perovskite material

2021 Fiscal Year Annual Research Report

• Project/Area Number: 21F21754
• Allocation Type: Single-year Grants
• Research Institution: Okinawa Institute of Science and Technology Graduate University
• Principal Investigator: Qi Yabing 沖縄科学技術大学院大学, エネルギー材料と表面科学ユニット, 教授 (10625015)
• Co-Investigator(Kenkyū-buntansha): MARIOTTI SILVIA 沖縄科学技術大学院大学, エネルギー材 料と表面科学ユニット, 外国人特別研究員
• Project Period (FY): 2021-11-18 – 2024-03-31
• Keywords: Perovskite passivation / self-assembly monolayers / bifacial solar cells

Outline of Annual Research Achievements

The JSPS fellow arrived in mid-December, hence she worked only for 3 and a half months in FY2021. During this time, the candidate accomplished safety and machine trainings and started preparing perovskite solar cell devices, achieving efficiencies up to 18.5% on p-i-n device architecture. In particular, she focused on using passivation molecules (phenetylammonium-based) to improve the device performance and stability. She used several equipment to understand the chemical effect on the perovskite surface, such as X-ray diffraction and X-ray photoelectron spectroscopy. This study is still ongoing. In addition, she developed a new method for the deposition of 2PACz self-assembly monolayer, used as hole transporting material in perovskite solar cells. The deposition, usually carried out using a solution process, is now performed via evaporation, and has shown to increase the device efficiency. Furthermore, she established a new collaboration with Prof. Narita (OIST), with whom she ideated a new self-assembly molecule with electron transport properties, to be used within the perovskite solar cell device. Finally, she used the JSPS funding to buy precursor materials for sputtering and atomic layer deposition. These materials were installed in existing machines and their deposition technique was tested, although their deposition method optimization is still ongoing. These materials will be used for preparing bifacial perovskite solar cells and modules, which represent a very interesting technology for the future of perovskite solar cells.

Current Status of Research Progress

2: Research has progressed on the whole more than it was originally planned.

Reason

The JSPS fellow has achieved most of her goals for the time being, progressing on equipment and machine training, device fabrication and characterization, designing and planning new experiments for preparing bifacial solar cells and establishing collaboration with colleagues within Prof. Qi Unit and within OIST, specifically with Prof. Narita.
Nevertheless, she is facing some issues in fabricating high performance devices, which are a key requirement for addressing manuscripts to high impact factor scientific journals. Up to now, the highest device efficiency obtained is 18.5 %, while only devices with efficiencies above 20 % can be considered as high-performance perovskite solar cells. The JSPS Fellow should therefore improve the device fabrication technique.

Strategy for Future Research Activity

The plan for FY2022 focuses on continuing the project started in FY2021. First, higher device performances of p-i-n perovskite solar cells need to be achieved. To do so, the JSPS Fellow is contemplating to use part of the FY2022 funding to buy additional equipment to improve device fabrication processes. Furthermore, additional perovskite compositions will be explored to study the passivation mechanism of the phenetylammonium-based molecules. At the moment, literature shows that there is a lack of knowledge about the passivation mechanism and it is therefore our goal to systematically study the interaction between the perovskite and the passivation molecules, using the large choice of surface analysis characterization present at OIST. In addition, IZO and SnO2 layer deposition optimization will be continued to allow the fabrication of bifacial perovskite solar cells, in which light can be absorbed from both sides of the device. Once prototypes of devices will show reasonable performances, large area devices will be fabricated. Concerning large area devices, the deposition method will need to be changed from solution process to evaporation, for highly uniform thin film depositions. As observed from the achievements obtained in FY2021, the evaporation of the hole transporting material has already shown to be a valid method for its deposition. As for the perovskite layer, chemical vapor deposition method will be considered, this being an effective method established by Prof. Qi and co-workers in the previous years.