[21p-E101-1~6] 12.5 Organic solar cells

[21p-E101-1] Voltage losses in nonfullerene acceptor-based organic solar cells

〇Yasunari Tamai^1,2, Toshiharu Saito¹, Shinichiro Natsuda¹, Hideo Ohkita¹ (1.Kyoto Univ., 2.JST PRESTO)

Keywords:Photon energy loss, non-radiative recombination, Charge transfer state

Here, we study photon energy losses in polymer solar cells based on PTB7-Th and various nonfullerene acceptors (NFAs). The open-circuit voltage of the PTB7-TH/IDT-2BR solar cell is higher than that of other NFA based devices up to 0.3 V while the optical bandgap of the IDT-2BR device is comparable to that of other devices. In order to discuss the origin of the small photon energy loss, voltage loss due to radiative and non-radiative recombination is estimated by an approach proposed earlier, which is based on the detailed-balance theory. As a result, we find reduced non-radiative voltage loss in the IDT-2BR device, meaning that photoluminescence quantum efficiency of charge transfer state is higher than that of other blends. On the other hand, non-radiative decay constants of charge transfer states are on the same order, suggesting that charge transfer states are more likely to deactivate radiatively in the IDT-2BR blend.