Photon Upconversion through a Cascade Process of Two-Photon Absorption in CsPbBr3 and Triplet-Triplet Annihilation in Organic Molecules
Akinori Saeki a b
a Department of Applied Chemistry, Graduate school of Engineering, Osaka University, 2-1 Yamadaoka, Suita, Osaka 565-0871, Japan.
b PRESTO, Japan Science and Technology Agency (JST), 4-1-8 Honcho, Kawaguchi, Saitama 332-0012, Japan.
Asia-Pacific International Conference on Perovskite, Organic Photovoltaics and Optoelectronics
Proceedings of International Conference on Perovskite and Organic Photovoltaics and Optoelectronics (IPEROP19)
Kyōto-shi, Japan, 2019 January 27th - 29th
Organizers: Hideo Ohkita, Atsushi Wakamiya and Mohammad Nazeeruddin
Oral, Akinori Saeki, presentation 026
Publication date: 23rd October 2018

Photon upconversion is an interesting nonlinear process that converts low-energy photons to high-energy photons, contrary to the normal energy relaxation process. This unique phenomenon has been utilized in bio-imaging and fabrication of nano-micro structures, and is potentially applicable in enhancing power conversion efficiency in a solar cell by converting inaccessible near-infrared (IR) sunlight to a photon energy above the bandgap energy. Two-photon absorption (TPA) and triplet-triplet annihilation (TTA) are the major processes, and many organic molecules and metal complexes have reportedly exhibited photon upconversion processes, such as green to blue and red to yellow.

Here, we report a TPA cascade process in inorganic perovskite quantum dots (PQDs) of CsPbBr3 and TTA in an organic molecule (9,10-diphenylanthracene, DPA) mediated by a octaethyl-porphyrinatoplatinum(II) (PtOEP) sensitizer[1]. This sequential energy transfer enables upconversion from four photons from a near-infrared femtosecond laser at 800 nm to one photon at 430 nm with a large anti-Stokes shift of ~1.3 eV. We characterize the energy transfer from PQDs to PtOEP by picosecond lifetime spectroscopy and a Stern-Volmer plot of the steady-state photoluminescence while considering dynamic and static quenching as well as trivial absorption and fluorescence resonant energy transfer (FRET). The serial connection of TPA and TTA achieved in a simple system opens up an attractive avenue in nonlinear photonics and harvesting of low-energy photons.

The author thank Mr. S. Izakura, Ms. W. Gu, and Mr. R. Nishikubo at Osaka University for their contribution to this work, and thank Prof. Takahiro Kozawa at The Institute of Scientific and Industrial Research (ISIR), Osaka University for his permission to use a femtosecond laser. This work was supported by the PRESTO program (Grant No. JPMJPR15N6) from the Japan Science and Technology Agency (JST) of Japan; the Japan Society for the Promotion of Science (JSPS) with the KAKENHI Grant-in-Aid for Scientific Research (A) (Grant No. JP16H02285); a grant from The Murata Science Foundation. R. N. acknowledges the financial support of a JSPS scholarship (No. 201820108).

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