GeI₂ Additive for High Optoelectronic Quality CsPbI₃ Quantum Dots and Their Application in Photovoltaic Devices

Journal Article · 13 January 2019 · Chemistry of Materials

DOI: https://doi.org/10.1021/acs.chemmater.8b03871 · OSTI ID:1513189

Liu, Feng ^[1]; Ding, Chao ^[1]; Zhang, Yaohong ^[1]; Kamisaka, Taichi ^[1]; Zhao, Qian ^[2]; Luther, Joseph M  ^[3]; Toyoda, Taro ^[1]; Hayase, Shuzi ^[4]; Minemoto, Takashi ^[5]; Yoshino, Kenji ^[6]; Zhang, Bing ^[7]; Dai, Songyuan ^[7]; Jiang, Junke ^[8]; Tao, Shuxia ^[8]; Shen, Qing ^[1]

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1. Univ. of Electro-Communications, Tokyo (Japan)
2. National Renewable Energy Lab. (NREL), Golden, CO (United States); Nankai Univ. (China)
3. National Renewable Energy Lab. (NREL), Golden, CO (United States)
4. Kyushu Inst. of Technology, Kitakyushu (Japan)
5. Ritsumeikan Univ., Shiga (Japan)
6. Miyazaki Univ. (Japan)
7. North China Electric Power Univ., Beijing (China)
8. Eindhoven Univ. of Technology (Netherlands)

Trioctylphosphine (TOP)-based syntheses of CsPbI₃ perovskite quantum dots (QDs) yield unprecedented high photoluminescence quantum yield (PL QY), lower Stokes shifts, and longer carrier lifetimes due to their enhanced crystallinity. This synthetic route relies on a heavily Pb-rich condition or a large Pb:Cs molar ratio in precursor solution to produce QDs with appropriate stoichiometry as well as to guarantee a good colloidal stability. The high Pb condition is achieved by a high concentration of PbI₂ prepared in TOP. Here we find such Pb-rich strategies can be avoided by providing additional iodine ions using other metal halide salts. In particular GeI₂, which contrary to PbI₂, readily dissolves in TOP. CsPbI₃ QDs prepared using PbI₂/GeI₂ combination show near-unity PL QY and improved chemical stability compared to the previous synthetic route. Furthermore, we find no sign of Ge incorporation in the QDs (compositionally or energetically). The ensuing QD solar cells deliver power conversion efficiency of 12.15% and retain 85% of its peak performance after storage over 90 days. The PbI₂/GeI₂ dual-source iodine synthetic approach presented here represents a more rational and robust route to high-quality CsPbI₃ QDs. to guarantee a good colloidal stability. The high Pb condition is achieved by a high concentration of PbI2 prepared in TOP. Here we find such Pb-rich strategies can be avoided by providing additional iodine ions using other metal halide salts. In particular GeI₂, which contrary to PbI₂, readily dissolves in TOP. CsPbI₃ QDs prepared using PbI₂/GeI₂ combination show near-unity PL QY and improved chemical stability compared to the previous synthetic route. Furthermore, we find no sign of Ge incorporation in the QDs (compositionally or energetically). The ensuing QD solar cells deliver power conversion efficiency of 12.15% and retain 85% of its peak performance after storage over 90 days. The PbI₂/GeI₂ dual-source iodine synthetic approach presented here represents a more rational and robust route to high-quality CsPbI₃ QDs.

• Research Organization: National Renewable Energy Laboratory (NREL), Golden, CO (United States)
• Sponsoring Organization: USDOE National Renewable Energy Laboratory (NREL), Laboratory Directed Research and Development (LDRD) Program
• Grant/Contract Number: AC36-08GO28308
• OSTI ID: 1513189
• Report Number(s): NREL/JA--5900-71882
• Journal Information: Chemistry of Materials, Journal Name: Chemistry of Materials Journal Issue: 3 Vol. 31; ISSN 0897-4756
• Publisher: American Chemical Society (ACS)Copyright Statement
• Country of Publication: United States
• Language: English