An Omnidirectionally Stretchable Photodetector Based on Organic–Inorganic Heterojunctions

Abstract

Omnidirectionally stretchable photodetectors are limited by difficulties in designing material and fabrication processes that enable stretchability in multiaxial directions. Here, we propose a new approach involving an organic-inorganic p-n heterojunction photodetector comprised of free-standing ZnO nanorods grown on a poly(3,4-ethylenedioxythiophene)-polystyrene sulfonate transport layer coated on a three-dimensional micropatterned stretchable substrate containing bumps and valleys. This structure allows for efficient absorption of stretching strain. This approach allows the device to accommodate large tensile strain in all of the directions. The device behaves as a photogated p-n heterojunction photodetector in which current modulation was obtained by sensing the mechanisms that rely on photovoltage and photogating effects. The device exhibits a high photoresponse to UV light and reliable electrical performance under applied stretching in uniaxial and omniaxial directions. Furthermore, the device can be easily and conformally attached to a human wrist. This allowed us to investigate the response of the device to UV light during human activity.

Materials and Designs for Wearable Photodetectors

“…Apart from nanostructured materials, organic materials such as poly(3‐hexylthiophene) (P3HT):[6,6]‐phenyl C 61 ‐butyric acid methyl ester (PCBM) blend, N , N ′‐bis(2‐phenylethyl)‐perylene‐3,4:9,10‐tetracarboxylic diimide (BPE‐PTCDI), poly[2,5‐bis(3‐tetradecylthiophen‐2‐yl)thieno[3,2‐b]thiophene](PBTTT):[6,6]‐phenyl‐C 61 ‐butyric acid methyl ester (PCBM), polyin‐dacenodithiophene‐pyridyl[2,1,3]thiadiazole‐cyclopentadithiophene (PIPCP), etc. are also built on polymer substrate to fabricate wearable PDs to take the advantage of their elasticity . A 3D printed organic PD was successfully fabricated with a stacking structure, using P3HT:PCBM as the active layer and poly(ethylenedioxythiophene):polystyrene sulfonate (PEDOT:PSS)/eutectic gallium indium (EGaIn) liquid metal as electrodes, as shown in Figure b .…”

“…Based on polymeric substrates, certain modifications have been made to these substrates to amplify the flexibility, bendability, and light absorption by forming crumpled structures . Kim et al proposed a stretchable photodetector based on a crumpled hybrid structure of graphene–gold nanoparticle with exceptional optoelectronic performance and mechanical stretchability at a tensile strain of ≈200% .…”

Over 16.7% Efficiency Organic‐Silicon Heterojunction Solar Cells with Solution‐Processed Dopant‐Free Contacts for Both Polarities

“…The commercially available conjugated organic polymer poly(3,4‐ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) is widely used as charge‐transport layer or transparent electrical contact in organic photovoltaic devices (OPVs), organic light‐emitting diodes (OLEDs), organic field‐effect transistors (OFETs), and many others devices due to its tunable optoelectronic properties, high transparency, ease of processing, and facile integration with functional materials. Most recently, PEDOT:PSS has been combined with crystalline silicon (c‐Si) substrate to replace the homogeneous buried junction traditionally used in photovoltaic devices, resulting in an organic/Si heterojunction solar cell (HSC) that can be formed without high‐temperature dopant‐diffusion processing .…”

Toward a Stretchable Organic Light‐Emitting Diode on 3D Microstructured Elastomeric Substrate and Transparent Hybrid Anode

“…The results in Figure c,d show that the Δ R / R 0 of the hybrid electrode on 3D‐MSES is much smaller than that of the hybrid electrode on a planar PDMS substrate by 22 times under stretching at a strain of 30% and 11.4 times under cyclic stretching for 20 000 cycles. The lack of change in resistance of the electrode on 3D‐MSES is due to the stress‐adaptable characteristics of this substrate, which allows the hybrid electrode to sustain a tensile strain …”