[20p-231C-1~9] Frontier of organic semiconductor crystals: Toward the Molecular Science of Quantum Liberated Electrons

[20p-231C-4] Small Open-Circuit Voltage Loss in Organic Solar Cells with Band Transport Molecule

〇Seiichiro Izawa^1,2, Naoto Shintaku^2,1, Kikuchi Mitsuru¹, Masahiro Hiramoto^1,2 (1.IMS, 2.SOKENDAI)

Keywords:Organic solar cells, Band transport, Non-radiative recombination

Reducing energy loss in open-circuit voltage (V_OC) is critically important for further enhancing the efficiency of organic solar cells (OSCs). Herein, we report an OSC with a band transport molecule realizing a very small V_OC loss. Charge delocalization in the molecule results in a unique property of no Stokes shift between the charge transfer (CT) state absorption and emission, i.e., lack of reorganization energy in between the CT and ground states. As a result, the nuclear wave function overlap of these states was reduced and non-radiative recombination, which nowadays is the biggest problem in OSCs, was largely suppressed. Our results demonstrate that charge delocalization that is the characteristic property in band transport molecules is the key to reducing the V_OC loss in OSCs.