Insight into trap state dynamics for exploiting current multiplication in organic photodetectors

Abstract

Trap‐induced current multiplication has received tremendous attention in organic photodetectors because it is not required for a pre‐amplifier circuit to read weak photocurrent signals. However, a plausible correlation between energy‐distin‐guishable trap states and device performance has not been established for guiding the device design, a task that remains a significant challenge. Here, we propose an ingenious strategy to demonstrate current multiplication by engineering an ultrathin fullerene (C60) film as hole trap or barrier layer, which illustrates trap‐state dynamics through systematical investigations on device current fluctuations in darkness and illumination conditions. The comparison of trap‐dependent performances between experimental and control devices clearly shows that the traps play a critical role in generating the multiplication effect. And shallow trap states are estimated to be more favorable for improving the device restorability. Thus, we anticipate that trap engineering, by selectively passivating deep traps whilst retaining shallow ones, will be a fruitful approach for further research, leading to high‐performance photodetectors with superior current multiplication and temporal response. (© 2013 WILEY‐VCH Verlag GmbH &Co. KGaA, Weinheim)

Recent Progress on Photomultiplication Type Organic Photodetectors

“…Peng et al. demonstrated PM type OPDs by engineering an ultrathin C 60 film as hole trap or barrier layer . The comparison of trap‐dependent performances between OPDs with or without C 60 interface obviously shows that the trap states in interfacial layer play an important role in inducing PM phenomenon, which results from the enhanced electron‐tunneling injection assisted by trapped photogenerated hole in C 60 interface.…”

“…Inspired by this work, a series of PM type OPDs are realized during the past decades . There are many efforts concentrated on the research of the working mechanisms of PM, the improvement of device performance, and the adjustment of spectral response window . However, to date, a comprehensive review about PM type OPDs has not yet been published.…”

Photovoltaic Action in Graphene–Ga2O3 Heterojunction with Deep‐Ultraviolet Irradiation

“…The rise time and decay time at the bias voltage of −1.5 V were estimated to be 3.21 s/26.68 s and 4.41 s/28.74 s, respectively. Thus, the photodiode gain with high EQE at a bias voltage can be explained with carrier multiplication due to hole trapping/release process . However, further detail study of the graphene‐Ga 2 O 3 interface are required to understand the photocarrier dynamics.…”

Development of High‐Sensitivity Poly(2,7‐(9,9‐dioctylfluorene)‐alt‐5,5‐(4′,7′‐di‐2‐thienylbenzo [c][1,2,5]thiadiazole)) Thin‐Film‐Based Phototransistors by the Ribbon‐Floating Film Transfer Method

“…Figure 3c shows the plot of photosensitivity of the ǁ and ⊥ oriented OFETs with respect to changing V GS for these OFETs. [40,41] Typical dependence of photosensitivity and responsivity over the V GS was observed, with maximum photosensitivity achieved before the onset of threshold voltage in these devices. In accordance with the previous observations, the ǁ OPT exhibited nearly 10 4 photosensitivity, when illuminated with green light (λ ¼ 522 nm).…”