Shaping Electroluminescence with a Large, Printed Bipolar Electrode Array: Solid Polymer Electrochemical Cells with Over a Thousand Light‐Emitting p–n Junctions

Abstract

The electroluminescence from a solid polymer light‐emitting electrochemical cell typically originates from a single, narrow p‐n or p‐i‐n junction. The bulk of the active material is non‐emitting and must be doped before an emitting junction is formed. Here, we show that the doping and emission profiles of a planar cell can be drastically altered with the introduction of a large printed array of ink‐jet‐printed bipolar electrodes. Redox doping reactions induced at the wireless bipolar electrodes led to the simultaneous formation of over a thousand highly emissive p‐n junctions uniformly distributed throughout the active layer of the large planar cell. The multi‐junction cell achieved an eightfold increase in light‐emitting area, a 14‐fold increase in peak current and ten times faster response speed compared to a single‐junction cell. Moreover, a giant open‐circuit voltage of approximately 35 V was observed when the doped cell was allowed to discharge. Here, bipolar electrochemistry offers a simple and yet elegant solution to engineer a better light‐emitting electrochemical cell.

Highly Soluble CsPbBr3 Perovskite Quantum Dots for Solution-Processed Light-Emission Devices

“…The same qualitative behavior was consistently observed also at other drive conditions (see Figure S5). This temporal improvement of the current and luminance are characteristic signatures of LEC operation, where it is directly effectuated by mobile ions redistributing and first forming EDLs at the electrode interfaces and subsequently performing electrochemical doping within the bulk of the active material. − The latter process results in the formation of a light-emitting p–n junction, when then p-type and n-type doping regions meet. Thus, it appears clear that mobile ions indeed are migrating within the PeQD active material when a voltage is applied and that these ions can perform electrochemical doping of the PeQDs.…”

Color Tuning of Multi-Resonant Thermally Activated Delayed Fluorescence Emitters Based on Fully Fused Polycyclic Amine/Carbonyl Frameworks

“…[47][48] The characteristic feature of LEC devices is the combination of mobile ions with the emissive organic semiconductor within the emissive layer. [49][50] These mobile ions redistribute when a voltage is applied, and enable p-type electrochemical doping of the organic semiconductor at the anode and n-type doping at the cathode. With time, these doping regions grow in size and make contact under the formation of a p-n junction.…”

Recent Advances in Bipolar Electrochemistry with Conducting Polymers

“…In a recent work, Hu et al. developed a planar PLEC array of 27×21 or 46×36 silver nanoparticle disks (Figure 7a) [71] . The wireless redox doping reactions induced on the BPEs lead to the simultaneous formation of over a thousand of light emitting p‐n junctions uniformly distributed throughout the PLEC.…”