| Outline of Annual Research Achievements |
We have advanced further on building strategies for high efficiency metal halide perovskite-based solar cells with up-scaling capabilities and long operational stabilities proposed in my original proposal. In FY2019, more than 18 peer-reviewed papers have been published, in which we acknowledged the funding support from Kakenhi Grant Number JP18K05266 (see Journal Articles section). I was invited to write 7 review articles [1, 3, 5, 8, 9, 13, 15] during FY2019. The main findings from our original research are summarized below:
(1) We continued to develop further strategies for realizing up-scaling processes based on solution and chemical vapor deposition (CVD) techniques [2, 13, 16, 18]. Carbon electrode-based perovskite solar cells have been recognized as a competitive candidate toward future practical applications [16]. We developed a low-cost carbon-based electrode that utilizes a cheap small-molecule semiconductor copper phthalocyanine (CuPc) as both the interface modifier and dopant [16].
(2) We improved our all-inorganic perovskite based solar cells [9, 12, 14]. Highly crystalline beta-CsPbI3 films with enhanced phase stability were demonstrated [14]. The effects of cracks and pinholes in the perovskite layer were mitigated by surface treatment with choline iodide, which increased the charge-carrier lifetime and improved the energy-level alignment. Our beta-CsPbI3 based perovskite solar cells showed high reproducibility and stable efficiencies reaching 18.4% under ~45 oC ambient conditions [14].
|
| Current Status of Research Progress |
Current Status of Research Progress
1: Research has progressed more than it was originally planned.
Reason
In addition to the descriptions provided in the “Summary of Research Achievements” section, below are further additional outcomes from the present research:
(1) The fabricated perovskite films are polycrystalline in nature, thus a significant high density of defects exists. Surface passivation employing multiple ligands strategy was introduced leading to passivation of uncoordinated Pb2+ defects as well as suppression of the formation of metallic-Pb defects [2]. Our proposed method was shown to significantly improve the performance of perovskite solar cells by employing multiple ligand strategy [2].
(2) The dynamic behavior and electronic properties of intrinsic defects in CH3NH3PbBr3 were explored at the atomic scale employing scanning tunneling microscopy (STM) [10]. We revealed the existence of vacancy defect clusters at the perovskite surface and the occurrence of vacancy-assisted transport of individual ions [10]. In another study, our STM studies provided the atomic arrangements of all-inorganic CsPbBr3 perovskites [4]. The stability evaluation performed employing X-ray photoelectron spectroscopy indicates a higher stability for CsPbBr3 in comparison with CH3NH3PbBr3, which is closely related to the low volatility of Cs from the perovskite surface [4]. These studies help in designing further strategies in a rational way such as the multiple ligands strategy [2] described above for improving the performance and stability of large area perovskite solar modules.
|
| Strategy for Future Research Activity |
We have accomplished the main tasks of module design optimization and successful large-area solar module fabrication by the CVD and other upscalable techniques [A1-A3]. For example, we demonstrated CVD grown large area solar modules with efficiencies of 9.3% fabricated on 10 cm x 10 cm substrates with enhanced stability [A3]. Our next goal is to further optimize the CVD protocols aiming at higher efficiencies as well as longer lifetimes. Efforts will be given to the STM technique on new perovskite materials as described in references [4, 10]. Atomic-level understanding of perovskite structure is crucial for the rational design approach of new photovoltaic materials.
[A1]L. Qiu, Z. Liu, L.K. Ono, Y. Jiang, D.-Y. Son, Z. Hawash, S. He, and Y.B. Qi, Scalable Fabrication of Stable High Efficiency Perovskite Solar Cells and Modules Utilizing Room Temperature Sputtered SnO2 Electron Transport Layer. Adv. Funct. Mater. 19 (2018) 1806779.
[A2]Y. Jiang, M. Remeika, Z. Hu, E.J. Juarez-Perez, L. Qiu, Z. Liu, T. Kim, L.K. Ono, D.-Y. Son, Z. Hawash, M.R. Leyden, Z. Wu, L. Meng, J. Hu, and Y.B. Qi, Negligible-Pb-Waste and Upscalable Perovskite Deposition Technology for High-Operational-Stability Perovskite Solar Modules. Adv. Energy Mater. 9 (2019) 1803047.
[A3]L. Qiu, S. He, Y. Jiang, D.-Y. Son, L.K. Ono, Z. Liu, T. Kim, T. Bouloumis, S. Kazaoui, and Y.B. Qi, Hybrid Chemical Vapor Deposition Enables Scalable and Stable Cs-FA Mixed Cation Perovskite Solar Modules with a Designated Area of 91.8 cm2 Approaching 10% Efficiency. J. Mater. Chem. A 7 (2019) 6920-6929.
|
