Using Bulk Heterojunctions and Selective Electron Trapping to Enhance the Responsivity of Perovskite–Graphene Photodetectors

• Published in: Advanced functional materials 2017-12, Vol.27 (47), p.n/a
• Main Authors: Qin, Liang, Wu, Liping, Kattel, Bhupal, Li, Chunhai, Zhang, Yong, Hou, Yanbing, Wu, Judy, Chan, Wai‐Lun
• Format: Article
• Language: English
• Subjects: bulk heterojunction; Butyric acid; Carrier lifetime; Current carriers; Electrons; Field effect transistors; GFET; Graphene; Heterojunctions; Materials science; organometallic hybrid perovskite; photodetectors; Photometers; Separation; Trapping
• ISSN: 1616-301X; 1616-3028
• DOI: 10.1002/adfm.201704173

Graphene field effect transistor sensitized by a layer of semiconductor (sensitizer/GFET) is a device structure that is investigated extensively for ultrasensitive photodetection. Among others, organometallic perovskite semiconductor sensitizer has the advantages of long carrier lifetime and solution processable. A further step to improve the responsivity is to design a structure that can promote electron–hole separation and selective carrier trapping in the sensitizer. Here, the use of a hybrid perovskite–organic bulk heterojunction (BHJ) as the light sensitizer to achieve this goal is demonstrated. Our spectroscopy and device measurements show that the CH3NH3PbI3–PCBM BHJ/GFET device has improved charge separation yield and carrier lifetime as compared to a reference device with a CH3NH3PbI3 sensitizer only. The key to these enhancement is the presence of [6,6]‐phenyl‐C61‐butyric acid methyl ester (PCBM), which acts as charge separation and electron trapping sites, resulting in a 30‐fold increase in the photoresponsivity. This work shows that the use of a small amount of electron or hole acceptors in the sensitizer layer can be an effective strategy for improving and tuning the photoresponsivity of sensitizer/GFET photodetectors. Mixing a small amount of electron acceptors ([6,6]‐phenyl‐C61‐butyric acid methyl ester) with hybrid organometallic perovskite significantly increases the photoresponsivity of perovskite–graphene photodetectors. It is found that the electron acceptors act as effective sites for both charge separation and electron trapping, which enhances the photoinduced change in the conductivity of the graphene channel.