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Nanographene-Based Heterojunctions for High-Performance Organic Phototransistor Memory Devices.

2023, Bai, Shaoling, Yang, Lin, Haase, Katherina, Wolansky, Jakob, Zhang, Zongbao, Tseng, Hsin, Talnack, Felix, Kress, Joshua, Andrade, Jonathan Perez, Benduhn, Johannes, Ma, Ji, Feng, Xinliang, Hambsch, Mike, Mannsfeld, Stefan C. B.

Organic phototransistors can enable many important applications such as nonvolatile memory, artificial synapses, and photodetectors in next-generation optical communication and wearable electronics. However, it is still a challenge to achieve a big memory window (threshold voltage response ∆V ) for phototransistors. Here, a nanographene-based heterojunction phototransistor memory with large ∆V responses is reported. Exposure to low intensity light (25.7 µW cm ) for 1 s yields a memory window of 35 V, and the threshold voltage shift is found to be larger than 140 V under continuous light illumination. The device exhibits both good photosensitivity (3.6 × 10 ) and memory properties including long retention time (>1.5 × 10  s), large hysteresis (45.35 V), and high endurance for voltage-erasing and light-programming. These findings demonstrate the high application potential of nanographenes in the field of optoelectronics. In addition, the working principle of these hybrid nanographene-organic structured heterojunction phototransistor memory devices is described which provides new insight into the design of high-performance organic phototransistor devices.

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Enhancing sub-bandgap external quantum efficiency by photomultiplication for narrowband organic near-infrared photodetectors

2021, Kublitski, Jonas, Fischer, Axel, Xing, Shen, Baisinger, Lukasz, Bittrich, Eva, Spoltore, Donato, Benduhn, Johannes, Vandewal, Koen, Leo, Karl

Detection of electromagnetic signals for applications such as health, product quality monitoring or astronomy requires highly responsive and wavelength selective devices. Photomultiplication-type organic photodetectors have been shown to achieve high quantum efficiencies mainly in the visible range. Much less research has been focused on realizing near-infrared narrowband devices. Here, we demonstrate fully vacuum-processed narrow- and broadband photomultiplication-type organic photodetectors. Devices are based on enhanced hole injection leading to a maximum external quantum efficiency of almost 2000% at −10 V for the broadband device. The photomultiplicative effect is also observed in the charge-transfer state absorption region. By making use of an optical cavity device architecture, we enhance the charge-transfer response and demonstrate a wavelength tunable narrowband photomultiplication-type organic photodetector with external quantum efficiencies superior to those of pin-devices. The presented concept can further improve the performance of photodetectors based on the absorption of charge-transfer states, which were so far limited by the low external quantum efficiency provided by these devices.