[10a-Z11-1~11] 12.5 Organic solar cells

[10a-Z11-11] Photon Upconversion at Organic Semiconductor Interface

〇Seiichiro Izawa^1,2, Masahiro Hiramoto^1,2 (1.IMS, 2.SOKENDAI)

Keywords:Organic semiconductor, Interface, Photon upconversion

Emission of high-energy photons by low-energy photoexcitation is called photon upconversion (UC). Herein, we discovered UC at the donor/acceptor (D/A) organic semiconductor interface. The UC emission follows the novel mechanism of triplet formation through free charge generation by near-infrared (NIR) photoexcitation and charge recombination at the D/A interface. The key to this mechanism is that the spin state becomes random after free charge separation; thus, triplet formation inside a sensitizer molecule, such as intersystem crossing, becomes unnecessary for UC. UC at the D/A interface has many advantages such as high efficiency with extremely low irradiation light intensity, minor metal, rare-earth or toxic elements free, low energy loss, and all-solid-state (thin film), compared to conventional UC systems. Thanks to these benefits, NIR imaging on flexible thin films by common LED light excitation become possible. This finding connects UC and organic semiconductors research fields and expands the applicability of UC for real device applications.