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

Abstract

Organic semiconductor crystals herald new opportunities for fabricating high‐performance optoelectronic devices, due to their intrinsic properties including outstanding charge transport properties, long exciton lifetime, and diffusion length. Despite remarkable progress in key figures of merit, the cut‐off frequency and responsivity are still lagging behind for most currently reported organic devices. Here, a high‐performance broadband vertical phototransistor based on rubrene single crystal, whose response covers the UV to visible range (300–650 nm) is reported. It shows a record‐high −3 dB bandwidth of ≈18 kHz and a maximum photoresponsivity of 105 A W−1. Due to the asymmetric Schottky contact and excellent light absorption of organic crystal, the device exhibits excellent zero‐bias photoresponse even under ultralow light illumination (≈114 fW). In particular, such organic vertical phototransistor holds good air stability and environmental robustness, and even without any form of encapsulation, no degradation of performance is observed for 2 months continuous operating. In addition, several single‐pixel imaging to show its potential for practical applications are demonstrated. The results provide a promising strategy to fabricate ultrafast and sensitive organic photodetectors for future video‐frame‐rate imaging.

Vertical Graphene/Pentacene Single Crystal/Graphene Transistors for Self‐Powered Weak Light Detection and High‐Speed Imaging

“…R . [34] Here NEP of our vertical device is estimated to be about 10.2 fW Hz −1/2 under zero gate bias, which is lower than that of the commercial silicon photodetector (30 fW Hz −1/2 ). [35] The specific detectivity (D*, units cm Hz 1/2 W −1 ) is another kernel parameter for the advanced photodetector, which describes the ability for sensing the weak light signal.…”

“…[ 33 ] For a low input bandwidth of 1 Hz, it can be calculated by the measured noise current:$$NEP = \frac{{\sqrt {\langle {i_n^2} \rangle/\Delta f} }}{R} \approx \frac{{\sqrt {S( f )} }}{R}$$. [ 34 ] Here NEP of our vertical device is estimated to be about 10.2 fW Hz −1/2 under zero gate bias, which is lower than that of the commercial silicon photodetector (30 fW Hz −1/2 ). [ 35 ] The specific detectivity (D*, units cm Hz 1/2 W −1 ) is another kernel parameter for the advanced photodetector, which describes the ability for sensing the weak light signal.…”

Organic–Inorganic Rubrene/WS2 Heterostructure for Broadband Detection and Polarization Imaging

“…Organic semiconductors are critical materials for photovoltaic power generation and sensor applications due to their high absorption coefficient (α ≈ 10 5 cm –1 ), good processability, and environmentally friendly fabrication. − While organic molecules are bound together by weak van der Waals forces, there is less overlap between molecular orbitals, which results in a low carrier mobility, especially for disordered organic films. The exciton diffusion length for the organic film is usually short (10–50 nm), much smaller than the light absorption length (∼1 μm), , which also restricts exciton utilization. Therefore, the performances of the device based on the individual organic channel are limited by insufficient charge collection.…”

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

“…Advanced photodetectors (PDs) are at the core of many technologies and applications, including optical communications, combustion flame monitoring, imaging sensors, night vision, remote controls and medical diagnoses. [1][2][3][4][5] At present, most of the commercial PDs with high sensitivity and fast response are fabricated using inorganic semiconductors, including traditional semiconductors (such as Si, Ge and GaAs), and thirdgeneration wide bandgap semiconductors (such as GaN, and SiC), because of their high mobility and stability. 6,7 However, inorganic materials always suffer from poor strain tolerance and strict preparation conditions, which would not meet the demand for next-generation highperformance, lowcost and flexible optoelectronic devices.…”