The solution‐processed organic photodetectors underpin an emerging technology with inherent implications in the biological sensors and imaging displays. Conventional organic photodiodes, the core element of an organic photodetector, rely mainly on fullerene‐based acceptors, which in combination with high and middle bandgap donors, limit the spectral photosensitivity to the visible range. Even in the case of low bandgap polymers the oscillator strength and thus the extinction coefficient are usually limited in the NIR due to the nature of molecular orbital hybridization. Instead, it is showed that pairing prototypical poly(3‐hexylthiophene) (P3HT) with rhodanine‐benzothiadiazole‐coupled indacenodithiophene (IDTBR), a nonfullerene electron acceptor absorbing beyond 750 nm, as the photoactive material of a simple photodiode results in a highly efficient organic photodetector with a record responsivity of 0.42 A W−1 and external quantum efficiency (EQE) of 69% in the NIR (755 nm). Nonfullerene‐based photodiodes are processed on amorphous silicon active matrix backplanes to realize large area flat panel photodetector imagers able to detect objects under visible and NIR light conditions with an exceptional combination of responsivity, dynamic response and image crosstalk.

A series of novel block copolymers, processable from single organic solvents and subsequently rendered amphiphilic by thermolysis, have been synthesized using Grignard metathesis (GRIM) and reversible addition–fragmentation chain transfer (RAFT) polymerizations and azide–alkyne click chemistry. This chemistry is simple and allows the fabrication of well-defined block copolymers with controllable block lengths. The block copolymers, designed for use as interfacial adhesive layers in organic photovoltaics to enhance contact between the photoactive and hole transport layers, comprise printable poly­(3-hexylthiophene)-block-poly­(neopentyl p-styrenesulfonate), P3HT-b-PNSS. Subsequently, they are converted to P3HT-b-poly­(p-styrenesulfonate), P3HT-b-PSS, following deposition and thermal treatment at 150 °C. Grazing incidence small- and wide-angle X-ray scattering (GISAXS/GIWAXS) revealed that thin films of the amphiphilic block copolymers comprise lamellar nanodomains of P3HT crystallites that can be pushed further apart by increasing the PSS block lengths. The approach of using a thermally modifiable block allows deposition of this copolymer from a single organic solvent and subsequent conversion to an amphiphilic layer by nonchemical means, particularly attractive to large scale roll-to-roll industrial printing processes.

No abstract

In the printing industry, the exploitation of triggerable materials that can have their surface properties altered on application of a post-deposition external stimulus has been crucial for the production of robust layers and patterns. To this end, herein, a series of clickable poly(R-alkyl p-styrene sulfonate) homopolymers, with systematically varied thermally-labile protecting groups, has been synthesised via reversible addition-fragmentation chain transfer (RAFT) polymerisation. The polymer range has been designed to offer varied post-deposition thermal treatment to switch them from hydrophobic to hydrophilic. Suitable RAFT conditions have been identified to produce well-defined homopolymers (Đ, M w /M n < 1.11 in all cases) at high monomer conversions (>80% for all but one monomer) with controllable molar mass. Poly(p-styrene sulfonate) with an isobutyl protecting group has been shown to be the most readily thermolysed polymer that remains stable at room temperature, and was thus investigated further by incorporation into a diblock copolymer, P3HT-b-PiBSS, by click chemistry. The strategy for preparation of thermal modifiable block copolymers exploiting R-protected p-styrene sulfonates and azide-alkyne click chemistry presented herein allows the design of new, roll-to-roll processable materials for potential application in the printing industry, particularly organic electronics.