A fully water-based patterning method for polymer semiconductors was developed and utilized to realize high-precision lateral patterning of various polymers. Water-borne polymer colloids, wherein hydrophobic polymers are dispersed in water with the assistance of surfactant molecules, possess a hydrophilic surface when printed onto a substrate. When this surface is exposed to a washing molecule, the surface of the polymer film recovers its original hydrophobic nature. Such surfactant-induced solubility control (SISC) enables environmentally benign, water-processed, and high-precision patterning of various polymer semiconductors with totally different solubilities, so that fully water-processed polymer organic image sensors (OISs) can be realized. B-/G-/R-selective photodiodes with a pixel size of 100 μm × 100 μm were fabricated and patterned by this water-based SISC method, leading to not only high average specific detectivity values (over 1012 Jones) but also narrow pixel-to-pixel deviation. Thanks to the superiority of the SISC method, we demonstrate the image capturing ability of OISs without B-/G-/R-color filters, from a fully water-based fabrication process.

We suggest a synthetic strategy to accelerate charge collection narrowing (CCN) of a polymer photodiode so that a well-defined color selectivity can be realized even with a thin film thickness, which is the most important requirement for commercial application of polymer photodiodes. A new polymer semiconductor POFPhDT2FBT is synthesized by copolymerizing a difluorobenzo­thiadiazole acceptor with a difluorinated donor moiety. A polymer photodiode with a structure of indium tin oxide/ZnO/POFPhDT2FBT:PC70BM bulk-heterojunction (BHJ) (550 nm)/MoO3/Ag exhibits a high peak detectivity of ∼6 × 1012 jones at 650 nm with a narrow full width at half-maximum <80 nm as well as a low noise equivalent power (4.83 × 10–14 W Hz–0.5), implying that CCN is achieved. This result is valuable as usually a BHJ film with a thickness of 550 nm exhibits a detectivity spectrum similar in shape to the absorption spectrum. We attribute the origin of the thin-film CCN in the POFPhDT2FBT:PC70BM BHJ to a weakened intramolecular charge transfer between the donor and acceptor of POFPhDT2FBT, leading to near-isotropic molecular orientations with a short-range π–π ordering, as confirmed by grazing-incidence X-ray diffraction. In other words, in the case of POFPhDT2FBT, a substantial number of photogenerated charges can remain as space charge carriers, thus enabling the CCN without using a thickness larger than 1 μm. This study shows the possibility of efficient realization of color selectivity of a polymer photodiode even at a film thickness of 550 nm of the active layer, which can contribute to the improvement of the integration of organic image sensors in the near future.

This study demonstrates a simple two-step post-treatment method for improving the thermoelectric power factor of low-cost poly(3,4-ethylenedioxythiophene):poly(4-styrenesulfonate) (PEDOT:PSS) films. The dry re-dispersible PEDOT:PSS pellets are cost-effective, however, they exhibit extremely low thermoelectric performance. On treating with ethylene glycol followed by hydrazine, the power factor of the PEDOT:PSS films increased from 0.0632±0.0097 μW m−1K−2 to 13.3±1.5 μW m−1K−2. The enhancement might be attributed to the effective removal of the free, non-complexed PSS chains and fine control of the oxidation level of PEDOT by the two-step post-treatment.

-In this paper, we propose a three-dimensional (3-D) channel estimation (CE) scheme to reduce the mean square error (MSE) in multi-antenna orthogonal frequency division multiplexing (OFDM) systems. Exploiting the channel correlation in the spatial domain as well as in the frequency and time domain, the proposed 3-D CE scheme can outperform conventional twodimensional (2-D) CE schemes, by either reducing the MSE with the same complexity or providing the same MSE performance with less complexity. Simulation results show that the proposed scheme is quite effective in the presence of spatial correlation.

The hole transport layer (HTL) plays a key role in inverted perovskite solar cells (PSCs), and nickel oxide has been widely adopted for HTL. However, a conventional solution‐processed bottom‐up approach for NiOx (S‐NiO) HTL fabrication shows several drawbacks, such as poor coverage, irregular film thickness, numerous defect sites, and inefficient hole extraction from the perovskite layer. To address these issues, herein, a novel NiOx HTL top‐down synthesis route via electrochemical anodization is developed. The basicity of the electrolyte used in anodization considerably influences electrochemical reactions and results in the structure of the anodized NiOx (A‐NiO). The optimized A‐NiO provides outstanding optoelectrical properties, including uniform film thickness, enhanced transmittance, deep‐lying valance band, low trap density, and better hole extraction ability from the perovskite. Owing to these advantages, the A‐NiO‐based inverted PSC exhibits an improved power conversion efficiency of 21.9% compared with 19.1% for the S‐NiO‐based device. In addition, the A‐NiO device shows a higher inlet and long‐term ambient stability than the S‐NiO device due to the superior hole transfer ability of A‐NiO, which suppresses charge accumulation between NiOx and the perovskite interface.