Diffusion-enhanced exciton dissociation in single-material organic solar cells

Single-material organic solar cells have recently attracted research attention due to their simplicity, morphological robustness and high yield of exciton dissociation. Using α-sexithiophene as a model system, we show that the single-event probability of the exciton dissociation at the boundaries of polycrystalline domains with different molecular orientation is extremely low (∼0.5%), while a high efficiency of charge generation is gained via hundred-fold crossings of the domain boundaries due to the long exciton diffusion length (∼45 nm). This journal i

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

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