Large‐Area, Semitransparent, and Flexible All‐Polymer Photodetectors

Abstract

Photodetectors, converting optical signals from specific wavelengths to electrical signals, have many applications on photoimaging, optical communication, and environmental monitoring. Solution-processed organic photodetectors (OPDs) based on organic materials emerge promise especially for wearable electronics and smart buildings. In this work, new all-polymer photodetectors (all-PPDs) are developed based on bulk-heterojunction active layers which incorporate a donor polymer and an acceptor polymer. The inverted all-PPDs exhibit outstanding external quantum efficiency over 70%, low dark current density (J d ) of 1.1 × 10 −8 A cm −2 , and high detectivity (D*) over 3.0 × 10 12 Jones with planar response over the entire visible range. It is one of the best-performing all-PPDs reported so far and is also comparable with many organic and inorganic photodetectors. By using lamination technique, large-area, semitransparent, flexible, and "fully" polymeric photodetectors are successfully fabricated for the first time, with D* over 10 11 Jones for double-side light detection. The results highlight the great potential for producing high-performance all-PPDs by taking advantages of various device architecture and solution-processing techniques.all-PPDs showed a high D* over 1.0 × 10 12 Jones at −3 V over the entire visible range. By introducing an electron-blocking layer via transfer-printing technique, we further reduced the J d to 1.1 × 10 −8 A cm −2 yet retained the high EQE, the D* was therefore tripled to 3.0 × 10 12 Jones at −3 V in the whole visible range. These EQE and D* results are among the bestperforming of all-PPDs to date. To demonstrate the potential of all-PPDs for versatile device configurations, we also fabricated and characterized large-area, semitransparent all-PPDs by using high-conductive poly(3,4-ethylenedioxythiophene): poly(styrenesulfonate) (PEDOT: PSS) as electrode, either on inflexible glass/indium tin oxide (ITO) substrates or on flexible polyethylene terephthalate (PET) substrates. Finally, large-area, semitransparent, and flexible all-PPDs were realized for the first time by using lamination technique. Both sides of the all-PPDs revealed almost symmetric photoresponse in the whole visible region with D* above 1.0 × 10 11 Jones.

All‐Polymer High‐Performance Photodetector through Lamination

“…But in practical condition, due to the disordered nature and unavoidable surface doping, the carrier density is always much higher than expected, which decrease the shunt resistance 23. It has been reported that increasing the thickness or adding electron or hole blocking layers can effectively reduce the dark current 24–26. Thicker active layer could decrease conductance and dark current, but it also increases the response time.…”

“…[23] It has been reported that increasing the thickness or adding electron or hole blocking layers can effectively reduce the dark current. [24][25][26] Thicker active layer could decrease conductance and dark current, but it also increases the response time. Blocking layers are usually a thin layer of donor at anode or acceptor at cathode, which have high bandgap and matched energy levels with electrodes that increases the barrier of reverse injection.…”

“…For both PTB7-Th and TQ1, BHJ devices have highest detectivity that reaches 10 11 Jones at the wavelength 700 nm. Detectivity as high as 10 12 Jones has been reported by some groups, [24,26,28,35] among which some considered shot noise only and might overestimate the number.…”

Omnidirectional Photodetectors Based on Spatial Resonance Asymmetric Facade via a 3D Self‐Standing Strategy

“…At present, optoelectronic materials can be only processed by spin‐coasting or vapor deposition‐based traditional fabrication methods into the planar structures. [ 7,32–34 ] Facile and reliable stereo micro/nanofabrication method for multiple materials with designed function units and controlled morphologies is therefore of great significance. The self‐assembly of inorganic and organic nanomaterials in liquids directed by a space‐confined template has been demonstrated to yield micro/nanopatterns for applications in wearable sensors, integrated circuits, flexible displays, and waveguide devices.…”

“…[ 38 ] Many researches focus on the quality of the planar photosensitive film to improve the responsivity of the photodetector. [ 7,32,37 ] Owing to the strong ability of concentrating light into subwavelength volumes, the nanostructured photodetector realizes the detection of the property of incident light, such as the wavelength, polarization direction, incident angle, etc. [ 43 ] To compare the angular‐sensing responsivity, the absorption efficiency was regarded as the parameter to measure the difference.…”