Gas-assisted blade-coating of organic semiconductors: molecular assembly, device fabrication and complex thin-film structuring

The competitive performance of optoelectronic devices based on advanced organic semiconductors increasingly calls for suitably scalable processing schemes to capitalise on their application potential. With performance benchmarks typically established by spin-coating fabrication, doctor-blade deposition represents a widely available roll-to-roll-compatible means for the preparation of large-area samples and establishing the device upscaling potential. However, the inherently slower film formation kinetics often result in unfavourable active layer microstructures, requiring empirical and material-inefficient optimisation of solutions to reach the performance of spin-coated devices. Here we present a versatile approach to achieving performance parity for spin- and blade-coated devices using in situ gas-assisted drying enabled by a modular 3D-printed attachment. This is illustrated for organic photodetectors (OPDs) featuring bulk heterojunction active layers comprising blends of P3HT and PM6 polymer donors with the nonfullerene acceptor ITIC. Compared to conventionally blade-coated devices, mild drying gas pressures of 0.5-2 bar yield up to a 10-fold enhancement of specific detectivity by maximising external quantum efficiency and suppressing dark-current. Furthermore, controlling gas flux distribution enables one-step fabrication of 1D chain conformation and 2D chain orientation patterns in, respectively, PFO and P3HT:N2200 blend films, opening the possibility for high-throughput fabrication of devices with complex structured active layers.

2,7,11,16-Tetra-tert-Butyl Tetraindenopyrene Revisited by an "Inverse" Synthetic Approach

A new synthetic route to tetraindenopyrene (TIP)—a bowl‐shaped cut‐out structure of C₇₀—is reported. The key step in this approach is a fourfold palladium‐catalyzed C−H activation that increases the yield more than 50 times in comparison to the approach originally described by Scott and co‐workers. Besides examination of its optoelectronic properties and study of its aggregation in solution, TIP was also re‐investigated by dispersion‐corrected DFT methods, which showed that dispersion interactions significantly increase the bowl‐to‐bowl inversion barrier. Furthermore, TIP was used as a semiconductor in p‐channel thin‐film transistors (TFTs).