Graphene/Organic Semiconductor Heterojunction Phototransistors with Broadband and Bi‐directional Photoresponse

Abstract

has been a challenge. [5,6] To enhance the absorption and photoresponse of graphene devices, researchers provide a series of strategies to interface graphene with light-absorbing semiconductors. [7][8][9][10][11][12][13][14][15][16] Early experimental studies on hybrid devices mainly focus on using one semiconductor layer, including colloidal quantum dots, [7,8] perov skites, [9] organic polymers, [10] single crystals, [16] 2D materials, [17] silicon, and other traditional materials. [11] More recently, improvement of device performance has been made by introducing PN junction bilayer absorbing layer. Incorporating graphene with a perovskite/ organic heterojunction or organic PN junction [14,15] is reported to improve both the photo responsivity and bandwidth. However, the limited narrow spectral range of light-absorbing layer causes ultrahigh photoconductive gain but at the same time sacrifices the detection spectral range. [18] In addition, a number of chemical approaches have been reported to synthesize the conjugated polymers/small molecules (typically with a bandgap of less than 1.6 eV) with appropriate energy gap and desirable photoelectric properties, but the device performance is still restricted. [19] So far the spectral range of graphene-based high gain photodetection is limited to typically 400-700 nm. [9,10,14,15,20,21] Herein, we explore a broadband (405-1550 nm) graphene/ organic semiconductor heterojunction phototransistors with bi-directional photoresponse (both positive and negative photocurrents) for the first time. Instead of broadening the absorption range of the semiconductor layer, our devices exploit ultrasensitive photoresponse at visible region, and the inverse photoresponse at near-infrared region without the need for cryogenics or adjusting gate voltage. Taking organic small molecule C 60 /pentacene heterojunction as the light-absorption layer, we achieve a highest responsivity of 9127 A W −1 , response time down to 275 µs, and external quantum efficiency up to 11.5% in visible regime and over 1800 A W −1 (0.063%) in near-infrared regime. Compared with previous work, our phototransistors not only have large built-in electric field at the C 60 /pentacene interface for high quantum efficiency, but also maintain an ultrasensitive response to the near-infrared region. The wavelength-dependent bi-directional response enables us to analyze the device mechanism. Our devices have potential applications in hyperspectral imaging.A graphene-semiconductor heterojunction is very attractive for realizing highly sensitive phototransistors due to the strong absorption of the semiconductor layer and the fast charge transport in the graphene. However, the photoresponse is usually limited to a narrow spectral range determined by the bandgap of the semiconductor. Here, an organic heterojunction (C 60 /pentacene) is incorporated on graphene to realize a broadband (405-1550 nm) phototransistor with a high gain of 5.2 × 10 5 and a response time down to 275 µs. The visible and near-infrared parts of the photor...

Ultrahigh Stability 3D TI Bi2Se3/MoO3 Thin Film Heterojunction Infrared Photodetector at Optical Communication Waveband

“…In particular, the most advanced infrared (IR) photodetector at optical communication waveband (1300–1650 nm) is of great significance, because it has a wide range of applications in the fields of military, information communication, and imaging . At present, two dimensional (2D) materials, due to their externally tunable bandgap and bound photoelectric properties, such as graphene, 2D transition metal dihalides (TMDs), and black phosphorus (BP), are becoming new stars in the field of telecommunications optical detection . However, the application of zero bandgap graphene is severely limited due to its low light absorption efficiency.…”

Design strategies for two‐dimensional material photodetectors to enhance device performance

“…This photodetector breaks the limit of the assisted absorbing materials' spectral range. More recently, bilayer or bulk hybrid enhanced graphene photodetectors for boosting detection performance . For excitons separation and trapping one type carrier, the type‐II band alignment meets requirements.…”

“…More recently, bilayer or bulk hybrid enhanced graphene photodetectors for boosting detection performance. [101][102][103][104][105][106] For excitons separation and trapping one type carrier, the type-II band alignment meets requirements. Compared to the single layer enhanced weak interaction between interfaces, bilayer or bulk hybrid assisted offer a more effective built-in field to promote the electron-hole separation.…”

Enhancement of Charge Transport in Polythiophene Semiconducting Polymer by Blending with Graphene Nanoparticles

“…However, composites of OSPs and GNPs can exhibit mutually beneficial effects, as they combine both semiconducting behavior of the polymers and enhanced charge transport characteristics of graphene . A typical demonstration of graphene/organic semiconductor heterojunction was previously realized as a highly photosensitive material due to strong absorption of organic semiconductor . Furthermore, the photoconductivity was found to be wavelength‐dependent, exhibiting opposite polarity due to the direction of the charge transfer or due to different drift velocity, which arises from the photoexcitation to different conducting channels .…”

“…A typical demonstration of graphene/organic semiconductor heterojunction was previously realized as a highly photosensitive material due to strong absorption of organic semiconductor . Furthermore, the photoconductivity was found to be wavelength‐dependent, exhibiting opposite polarity due to the direction of the charge transfer or due to different drift velocity, which arises from the photoexcitation to different conducting channels . Such tunability will enable new functionalities in future electronic devices.…”