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

Abstract

Organic materials have drawn significant interest for nextgeneration advanced optoelectronic devices or systems owing to their extraordinary light absorption, intrinsic flexibility, and low-temperature, largescale processability. While for high-performance organic photodetectors, their restricted carrier mobility, limited diffusion length, and high binding energy of Frenkel excitons have long been regarded as the major challenges. In this paper, we report a sensitive organic rubrene crystal/graphene heterostructure photodetector. Especially, using an asymmetrical van der Waals stacking configuration, we realized self-powered photon detection in such a graphene-based organic heterostructure device. Long-range exciton diffusion of the rubrene single crystal, the efficient exciton dissociation, and the ultrafast charge transfer near the heterointerface enabled several commendable performances, including the great responsivity of 8 × 10 5 A/W, specific detectivity of >10 12 Jones, and a fast response speed (ca. 20/ 70 μs). Encouragingly, the device exhibits excellent mechanical flexibility, remaining good conductivity, and stable light detection, even under harsh strain and after hundreds of cycles. Utilizing their outstanding photoresponse, we demonstrate fast-speed imaging applications on rigid and flexible substrates. Our work offers a practical strategy for developing high-performance, self-powered organic photodetectors for future wireless photon detection and high-speed imaging applications.

Asymmetric Schottky Barrier in Rubrene Transistor via Monolayer Graphene Insertion toward Self-Powered Imaging

“…The anisotropy of rubrene single crystals allows us to study their optical properties using polarization optical microscopy (POM). Figure 1d shows the POM image of a typical rubrene crystal under a 532 nm LED light source [30]. Figure 1d shows the steady-state photoluminescence spectrum (PL) characterization from the ab face of the rubrene sample.…”

Recent advances in enhancing the photodetector performance of 2D materials by combining them with organic thin films

“…While rubrene/graphene heterojunction photodetectors have been proposed previously, 116 they did not achieve self-powered capabilities. The rubrene/graphene heterojunction photodetector presented by Zhao et al 130 offers self-powered photon detection, high responsivity (8 × 10 5 A W −1 ), high detectivity (>10 12 Jones), and fast response times (20/70 μs). These attributes are primarily due to the long exciton diffusion length in the rubrene/graphene heterojunction's rubrene single crystal and graphene's high mobility.…”

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.…”