[TuP3H] H. Flexible materials

2:00 PM - 4:00 PM JST(5:00 AM - 7:00 AM UTC)

[TuP3H-04] Charge-Carrier Recombination in PBDB-T:ITIC Organic Photovoltaic Devices with and without a Processing Additive

〇Yuta Takenaka¹, Takashi Nagase¹, Hiroyoshi Naito^1,2, Takashi Kobayashi¹ (1. Osaka Metropolitan Univ. (Japan), 2. Ritsumeikan Univ. (Japan))

Processing additives are widely used to control the interpenetrating donor/acceptor network to achieve high-efficiency organic photovoltaic (OPV) devices. Here, we investigate the effects of a processing additive, 1,8-diiodooctane (DIO), on charge-carrier recombination using conventional and inverted PBDB-T:ITIC OPV devices processed with and without DIO. Recombination was examined by modulated photocurrent (MPC) and photovoltage (MPV) spectroscopy. An increase in the open-circuit voltage is observed in DIO-processed inverted devices, suggesting suppressed charge-carrier recombination. However, the bimolecular recombination coefficient, evaluated from MPV measurements, remains nearly constant regardless of architecture and additive processing. In contrast, we find that the first-quadrant signal in the Nyquist plot of the MPC response, which has been attributed to Shockley–Read–Hall recombination, disappears in DIO-processed inverted devices. Analysis of the J–V characteristics supports this conclusion. The selective suppression of Shockley–Read–Hall recombination in DIO-processed inverted OPVs is likely due to a previously reported vertical composition gradient in PBDB-T:ITIC, which forms an ITIC-rich region near the transparent electrode, thereby favoring the inverted architecture.