Ultrafast and Sensitive Self‐Powered Photodetector Based on Graphene/Pentacene Single Crystal Heterostructure with Weak Light Detection Capacity

Abstract

Organic materials exhibit efficient light absorption and low‐temperature, large‐scale processability, and have stimulated enormous research efforts for next‐generation optoelectronics. While, high‐performance organic devices with fast speed and high responsivity still face intractable challenges, due to their intrinsic limitations including finite carrier mobility and high exciton binding energy. Here an ultrafast and highly sensitive broadband phototransistor is demonstrated by integrating high‐quality pentacene single crystal with monolayer graphene. Encouragingly, the −3 dB bandwidth can reach up to 26 kHz, which is a record‐speed for such sensitized organic phototransistors. Enormous absorption, long exciton diffusion length of pentacene crystal, and efficient interfacial charge transfer enable a high responsivity of >105 A W−1 and specific detectivity of >1011 Jones. Moreover, self‐powered weak‐light detection is realized using a simple asymmetric configuration, and the obvious zero‐bias photoresponses can be displayed even under 750 nW cm−2 light intensity. Excellent response speed and photoresponsivity enable high‐speed image sensor capability in UV‐Vis ranges. The results offer a practical strategy for constructing high‐performance self‐powered organic hybrid photodetectors, with strong applicability in wireless, weak‐light detection, and video‐frame‐rate imaging applications.

Organic photodetectors based on pentacene single crystals with fast response and flexibility

“…The vibrational peak at 1372 cm À1 belongs to the benzene ring stretching, and Raman peaks at 1159 cm À1 and 1178 cm À1 should be attributed to the E 2g vibration of the benzene ring, which correspond to the results of pentacene crystals. 24 This high crystallinity is also confirmed by the selected area electron diffraction (SAED) pattern shown in Fig. 1e, which exhibits well-defined individual electron diffraction spots rather than circular lines.…”

“…. 24 Based on this simplified equation, we calculate D* for the different wavelength irradiation, and the highest value of D* is about 10 9 -10 10 Jones, as shown in Fig. 3i.…”

“…At small measurement bandwidth of Δ f = 1, the specific detectivity D * can be simplified as . 24 Based on this simplified equation, we calculate D * for the different wavelength irradiation, and the highest value of D * is about 10 9 –10 10 Jones, as shown in Fig. 3i.…”

Ultrafast and Stable Organic Single‐Crystal Vertical Phototransistor for Self‐Powered Photodetection and High‐Speed Imaging

“…For the graphene/ rubrene interface, the photocurrent is also obvious when the laser signal is beyond the overlap (see Figure S9, Supporting Information), while the photocurrent is almost none for the graphene/pentacene system without the waveguide effect. [30] This asymmetrical Schottky barrier and intrinsic band bending enabled a self-powered photon detection capacity in Figure 3f, where the short-circuit current increased with the light power. Thanks to excellent absorption of rubrene crystal and efficient depletion region due to shortened channel, the salient zero-bias photoresponses can be distinguished even under weak light irradiation (114 fW of 532 nm, see Figure 3g).…”

Self-Powered Organic Phototransistors with Asymmetrical van der Waals Stacking for Flexible Image Sensors

“…Therefore, we figured out the photoresponsivity of device using R = I ph / P in , and it can reach to ∼8 × 10 5 A/W at V DS = 50 mV (Figure f), which reaches up to in first-class as compared to the previously reported organic photodetector. − Under zero gate voltage, the responsivity is lower than that of other gate conditions due to a weakened built-in electric filed. The R reduces with the incident illumination levels, which is related to the saturated absorption, increased recombination probability and weakened built-in field Figure g depicted the photocurrent ( I ph = | I light – I dark |) as a function of bias voltage ( V DS ) under the different illumination.…”