The great potential of solution‐processed metal nanowire networks utilized as a transparent electrode has attracted much attention in the last years. Typically, silver nanowires are applied, although their replacement by more abundant and cheaper materials is of interest. Here, a hydrazine‐free synthesis route for high aspect ratio copper nanowires is used to prepare conductive networks showing an enhanced electrode performance. The network deposition is done with a scalable spray‐coating process on glass and on polymer foils. By a pressing or an annealing step, highly conductive transparent electrodes are obtained, and they reveal transmittance‐resistance values similar to indium tin oxide (ITO) and networks made of silver nanowires. The application potential of the copper nanowire electrodes is demonstrated by integrating them into an evaporated small‐molecule organic solar cell with 3% efficiency.

We present a novel top-electrode spray-coating process for the solution-based deposition of silver nanowires (AgNWs) onto vacuum-processed small molecule organic electronic solar cells. The process is compatible with organic light emitting diodes (OLEDs) and organic light emitting thin film transistors (OLETs) as well. By modifying commonly synthesized AgNWs with a perfluorinated methacrylate, we are able to disperse these wires in a highly fluorinated solvent. This solvent does not dissolve most organic materials, enabling a top spray-coating process for sensitive small molecule and polymer-based devices. The optimized preparation of the novel AgNW dispersion and spray-coating at only 30 °C leads to high performance electrodes directly after the deposition, exhibiting a sheet resistance of 10.0 Ω □(-1) at 87.4% transparency (80.0% with substrate). By spraying our novel AgNW dispersion in air onto the vacuum-processed organic p-i-n type solar cells, we obtain working solar cells with a power conversion efficiency (PCE) of 1.23%, compared to the air exposed reference devices employing thermally evaporated thin metal layers as the top-electrode.

We measure basic network parameters of silver nanowire (AgNW) networks commonly used as transparent conducting electrodes in organic optoelectronic devices. By means of four point probing with nanoprobes, the wire-to-wire junction resistance and the resistance of single nanowires are measured. The resistance RNW of a single nanowire shows a value of RNW=(4.96±0.18) Ω/μm. The junction resistance RJ differs for annealed and non-annealed NW networks, exhibiting values of RJ=(25.2±1.9) Ω (annealed) and RJ=(529±239) Ω (non-annealed), respectively. Our simulation achieves a good agreement between the measured network parameters and the sheet resistance RS of the entire network. Extrapolating RJ to zero, our study show that we are close to the electrical limit of the conductivity of our AgNW system: We obtain a possible RS reduction by only ≈20% (common RS≈10 Ω/sq). Therefore, we expect further performance improvements in AgNW systems mainly by increasing NW length or by utilizing novel network geometries.

The surfactant polyvinylpyrrolidone (PVP) commonly used to synthesize silver nanowires (AgNW) in solution is known to negatively affect the performance of nanowire-based thin film electrodes. An insulating shell of the polymer hinders tight contact between the nanowires themselves and between the nanowires and substrate, resulting in high sheet resistance of the freshly prepared nanowire films. Here, we develop a simple low-temperature method allowing us to reduce the sheet resistance of AgNW networks and simultaneously improving the optical transmittance. The method is based on the capacity of PVP to absorb moisture which results in a strong decrease in the glass transition temperature of the polymer.The latter leads to softening effects, causing a reduced wire contact resistance already at 60 C for 90 nm thick AgNWs and even at 45 C for 35 nm thick AgNWs. As a result, the sheet resistances of the thin film electrodes treated by our method are near to the values conventionally obtained after thermal annealing at temperatures between 140-250 C. Our humidity assisted low temperature approach is especially advantageous for organic electronics and fabricating devices on thermally sensitive transparent flexible foils. † Electronic supplementary information (ESI) available: Changes in total transmittance DT vs. initial total transmittance; transmittance spectra of NW-35 electrode vs. annealing time; SEM images of a NW-35 electrode on glass; sheet resistance vs. annealing time at a constant temperature of 60 C and different RH values; SEM image, transmittance and reectance spectra of NW-90 electrode on PEN foil. See

The anisotropy in semiconductor nanoplatelets (NPLs) is reflected in the anisotropy of their crystal structure and organic ligand shell, which can be used for creating new semiconductor heterostructures. This work demonstrates the synthesis of core/shell NPLs containing zero-dimensional (0D) Cd x Hg1–x Se domains embedded in CdSe NPLs via cation exchange. The strategy is based on the different accessibility of definite regions of the NPLs for incoming cations upon time-limited reaction conditions. The obtained heterostructures were successfully overcoated with a Cd y Zn1–y S shell preserving their two-dimensional (2D) morphology. The NPLs exhibit bright photoluminescence in the range of 700–1100 nm with quantum yields up to 55%, thus making them a prospective material for light-emitting applications in the near-infrared spectral range.