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

Abstract

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 CH 3 NH 3 PbI 3 -PCBM BHJ/GFET device has improved charge separation yield and carrier lifetime as compared to a reference device with a CH 3 NH 3 PbI 3 sensitizer only. The key to these enhancement is the presence of [6,6]-phenyl-C 61 -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.

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.…”

“…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 …”

“…Therefore, for improving charge separation efficiency, exciton diffusion length should be limited on the order of 5 to 10 nm . Chen et al investigated bilayer small molecule (PTCDA/pentacene) enhanced graphene phototransistor for the first time, it shows mechanism behind and extraordinary performance (Figure E) . When the graphene is n‐doping by the gate control, the device exhibits a intrinsic response time of 28 μs (Figure F).…”

“…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.…”

“…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. 101 A great number of type-II heterojunction have been widely employed in OSC field. [107][108][109][110][111][112][113] Two mainly donor-acceptor system including the organic bulk and planar heterojunction are the ideal assisted enhanced materials.…”