Aerosol‐Jet Printed Flexible Organic Photodiodes: Semi‐Transparent, Color Neutral, and Highly Efficient

Abstract

which makes AJP therefore a suitable candidate for all of the above-mentioned applications.In this work, we present fl exible OPDs fully printed by AJP with equivalent performance to state-of-the-art devices fabricated on rigid substrates by conventional deposition methods. The OPDs exhibit a device transparency of ≈15% while reaching external quantum effi ciency (EQE) values of up to 50%, a high spectral response (SR) (≥0.26 A W −1 ), a specifi c detectivity ( D *) >10 11 Jones from top and bottom illumination, respectively, as well as a bandwidth up to ≈300 kHz at −3 V reverse bias. Furthermore, the devices are exceptionally color neutral and thus very well suited for see through or building-integrated applications.Figure 1 a presents a scheme of the device architectures and energy band diagrams of the two types of printed OPDs fabricated in the so-called inverted confi guration (with the n -contact as the bottom electrode). In this work, two types of OPDs were fabricated. First, OPDs have been deposited via AJP on the top of an ITO covered PET foil (see Figure 1 a(i)). Second, the ITO was replaced by a conductive PEDOT:PSS electrode. The ITOfree device architecture can be seen in Figure 1 a(ii). Aside from the bottom electrode, all devices comprised the same layer stack. In both device confi gurations, a layer of aluminum doped zinc oxide (AZO) nanoparticles was used as the hole-blocking layer for the cathode. The n -doped AZO offers three orders of magnitude higher electrical conductivity compared to intrinsic ZnO, which allows for deposition of thicker layers. [ 11 ] The active layer and the complementary anode consisted of a blended polythieno[3,4b ]-thiopheneco -benzodithiophene (PTB7) and [6,6]-phenyl C71-butyric acid methyl ester (PC70BM) bulk heterojunction and conductive PEDOT:PSS, respectively. Figure 1 b shows photographs of an ITO-free sample containing four fully printed semitransparent OPD pixels fabricated with different active layer thicknesses. The top panel of Figure 1 b exemplifi es the mechanical fl exibility of the OPDs fabricated on fl exible PET substrates, as well as the feasibility to produce a series of devices using the process presented in this work.Printing parameters such as printing speed, material fl ow, and sheath gas fl ow rates were optimized in order to obtain smooth and homogeneous layers suitable for device fabrication. With the optimized printing parameters, the surface modulation, resulting from the sequential printing path, as well as coffee stain effects at the edge of the printed areas were drastically reduced. A detailed explanation of the optimization of the layer deposition is shown in the fi rst section of the Supporting Information ( Figure S1 and Table S1), while the working principle of the AJP can be found elsewhere. [ 12 ] In order to confi rm that the chemical structure of the active materials was Optical sensors have become the focus of great industrial and academic research interest due to their applications in environmental monitoring, [ 1 ] the automotive...

Visible and Near‐Infrared Imaging with Nonfullerene‐Based Photodetectors

“…Recently, we observed unusually low recombination rates, enabling close to unchanged device performance for NFA‐based solar cells with up to 450 nm active layer thickness . This observation anticipates a similarly advantageous impact on the performance of OPDs, where thick active layers usually contribute to reduced dark currents . Thus, bulk heterojunction (BHJ) organic photodetectors consisting of a donor polymer and an NFA represent a chance to move the detection into the NIR spectral region without sacrificing EQE.…”

Organic Photodiodes: The Future of Full Color Detection and Image Sensing

“…While many molecular materials are processed by evaporation, [ 105 ] there are examples whereby they are solution processed. [ 37,106 ] Macromolecules such as dendrimers and polymers can be processed from solution using techniques such as aerosol-jet printing, [ 107 ] spin-coating, [ 108 ] inkjet-printing, [ 109,110 ] screen printing, [ 111 ] or spray-coating. [112][113][114][115] …”

Fully Digitally Printed Image Sensor Based on Organic Photodiodes

“…The viability of these processes for the fabrication of entirely printed OPDs has been demonstrated in our work and by others . However, most of the reports so far are limited to single devices.…”

“…Aside from the periodic stitching errors, one can clearly identify the protruding SU‐8 pattern as well as the PTB7:PC 70 BM area and the polymeric PEDOT:PSS electrodes. A detailed morphological study of the printed layers and the influence of various processing parameters can be found in our previous publications, where we have demonstrated high quality layer and material properties leading to full functionality of our devices …”

“…Furthermore, the mechanical properties of these plastic materials represent a unique characteristic for the fabrication of flexible or conformable devices with potential application in wearable, smart packaging, or medical technologies . Beyond that, the fabrication of optoelectronic devices via digital printing technologies, e.g., Inkjet printing and spray coating processes like Aerosol Jet printing (AJ), enables an exceptional customizability as well as a cost‐effective fabrication of devices perfectly matching the individual application requirements.…”