Investigation of high-efficiency formamidinium methyl-ammonium perovskite-based photovoltaic cells

Faculty Development Competitive Research Grant Program 2018-2020

The development of cost-effective and highly efficient renewable energy sources is one of the biggest challenges for the 21st Century. At present the total power consumption worldwide is ~18 TW and is projected to grow by as much as one-third by 2035. Continued dependence on fossil fuels will result in irreversible damages to the environment with devastating consequences. According to the International Energy Agency nearly half of the net increase in electricity generation will come from renewables.1 Hence, the development of high efficiency photovoltaic cells will be critical for meeting the future global energy demands. Among the various photovoltaic materials, organic-inorganic perovskite thin films have drawn significant attention in recent years due to its tremendous progress in the development of high efficiency solar cells.2-11
In this proposal, we have outlined a program for the investigation of high efficiency Formamidinium Methylammonium lead halide (FMPX) and Caesium Formamidinium Methylammonium lead halide (CFMPX) based perovskite solar cells (PSCs).12,13 This material has significant advantages over the conventional PVC based on the methyl ammonium lead tri-iodide (MAPI) thin film in terms of material stability which is a crucial for the successful commercialization of PSCs. We propose to conduct the following studies:
1.) Investigation of oxygen annealing of defect states in FMPX and CFMPX thin films – The significance of this study is mainly due to the tremendous deleterious effects of the defect states on the performance of the photovoltaic devices. To the best of our knowledge, so far there is no systematic studies on the passivation of the material defects of the FMPX and CFMPX films by oxygen annealing.
2.) Investigation of hybrid chemical vapor deposition (HCVD) technique on the growth of FMPX and CFMPX thin films – This process was originally pioneered by the PI for the growth high quality CH3NH3PbI3 (MAPI) thin films. The technique is now extended to the FMPX and CFMPX thin films. This is expected to have significant impact on both the efficiency and the stability of the device as well as the potential large-scale production of the perovskite thin films.
3.) Investigation of the optimal device structure for high performance PSCs – While TiO2 is by far the most common material for the electron transport layer (ETL), recent results had implicated TiO2 as a source for device instability due to the photo-catalytic effect at the perovskite/TiO2 interface. We will investigate means to enhance the stability of the devices such as the use of SnO2 as the ETL to avoid materials degradation due to photo-catalytic effects. This study is crucial for the commercialization of the PSCs as device stability is the pre-requisite for any practical application of the device. Detailed degradation of the device over time will be performed.