Solution-processable organic semiconductors are central to developing viable printed electronics, and performance comparable to that of amorphous silicon has been reported for films grown from soluble semiconductors. However, the seemingly desirable formation of large crystalline domains introduces grain boundaries, resulting in substantial device-to-device performance variations. Indeed, for films where the grain-boundary structure is random, a few unfavourable grain boundaries may dominate device performance. Here we isolate the effects of molecular-level structure at grain boundaries by engineering the microstructure of the high-performance n-type perylenediimide semiconductor PDI8-CN2 and analyse their consequences for charge transport. A combination of advanced X-ray scattering, first-principles computation and transistor characterization applied to PDI8-CN2 films reveals that grain-boundary orientation modulates carrier mobility by approximately two orders of magnitude. For PDI8-CN2 we show that the molecular packing motif (that is, herringbone versus slip-stacked) plays a decisive part in grain-boundary-induced transport anisotropy. The results of this study provide important guidelines for designing device-optimized molecular semiconductors.

Top‐gate n‐TFTs and CMOS circuits on plastic substrates based on solution‐processed n‐ and p‐channel semiconductors and polymeric dielectrics have been fabricated. These unencapsulated devices exhibit good performance characteristics in ambient.

Despite their favorable electronic and structural properties, the synthetic development and incorporation of thiazole-based building blocks into n-type semiconductors has lagged behind that of other π-deficient building blocks. Since thiazole insertion into π-conjugated systems is synthetically more demanding, continuous research efforts are essential to underscore their properties in electron-transporting devices. Here, we report the design, synthesis, and characterization of a new series of thiazole–thiophene tetra- (1 and 2) and hexa-heteroaryl (3 and 4) co-oligomers, varied by core extension and regiochemistry, which are end-functionalized with electron-withdrawing perfluorohexyl substituents. These new semiconductors are found to exhibit excellent n-channel OFET transport with electron mobilities (μ e ) as high as 1.30 cm2/(V·s) (I on/I off > 106) for films of 2 deposited at room temperature. In contrary to previous studies, we show here that 2,2′-bithiazole can be a very practical building block for high-performance n-channel semiconductors. Additionally, upon 2,2′- and 5,5′-bithiazole insertion into a sexithiophene backbone of well-known DFH-6T, significant charge transport improvements (from 0.001–0.021 cm2/(V·s) to 0.20–0.70 cm2/(V·s)) were observed for 3 and 4. Analysis of the thin-film morphological and microstructural characteristics, in combination with the physicochemical properties, explains the observed high mobilities for the present semiconductors. Finally, we demonstrate for the first time implementation of a thiazole semiconductor (2) into a trilayer light-emitting transistor (OLET) enabling green light emission. Our results show that thiazole is a promising building block for efficient electron transport in π-conjugated semiconductor thin-films, and it should be studied more in future optoelectronic applications.

In organic field-effect transistors, the structure of the constituent molecules can be tailored to minimize the disorder experienced by charge carriers. Experiments on two perylene derivatives show that disorder can be suppressed by attaching longer core substituents - thereby reducing potential fluctuations in the transistor channel and increasing the mobility in the activated regime - without altering the intrinsic transport properties.

Metal oxide (MO) semiconductor thin films prepared from solution typically require multiple hours of thermal annealing to achieve optimal lattice densification, efficient charge transport, and stable device operation, presenting a major barrier to roll-to-roll manufacturing. Here, we report a highly efficient, cofuel-assisted scalable combustion blade-coating (CBC) process for MO film growth, which involves introducing both a fluorinated fuel and a preannealing step to remove deleterious organic contaminants and promote complete combustion. Ultrafast reaction and metal–oxygen–metal (M-O-M) lattice condensation then occur within 10–60 s at 200–350 °C for representative MO semiconductor [indium oxide (In2O3), indium-zinc oxide (IZO), indium-gallium-zinc oxide (IGZO)] and dielectric [aluminum oxide (Al2O3)] films. Thus, wafer-scale CBC fabrication of IGZO-Al2O3 thin-film transistors (TFTs) (60-s annealing) with field-effect mobilities as high as ∼25 cm2 V−1 s−1 and negligible threshold voltage deterioration in a demanding 4,000-s bias stress test are realized. Combined with polymer dielectrics, the CBC-derived IGZO TFTs on polyimide substrates exhibit high flexibility when bent to a 3-mm radius, with performance bending stability over 1,000 cycles.

We report two new low band-gap conjugated polymers containing dipyrrolo[2,3-b:2',3'-e]pyrazine-2,6(1H,5H)-dione (PzDP), PPzDPDP-BT and PPzDPDP-TT, both showing ambipolar transport in organic thin film transistors (OTFTs), with hole mobility up to 0.066 cm(2) V(-1) s(-1), electron mobility up to 0.021 cm(2) V(-1) s(-1), and high current on-to-off ratios of 10(5)-10(6).

The electron acceptor building block for π-conjugated copolymers, 3,6-dithiophen-2-yl-diketopyrrolo[3,2-b]pyrrole (isoDPPT), was synthesized following two routes. The comparison between isoDPPT and widely investigated 3,6-dithiophen-2-yl-diketopyrrolo[3,4-c]pyrrole (DPPT) in terms of molecular orbital computations, single crystal X-ray diffraction, optical absorption and cyclic voltammogram was utilized to elucidate structural and electronic structure differences between the two cores. Both units are found to be planar in the solid state, exhibit similar LUMO energy, however, isoDPPT exhibits a much deeper HOMO energy. Six isoDPPT-based polymers with optical bandgaps spanning from 1.44 to 1.76 eV were synthesized by copolymerizing isoDPPT with the following building blocks: 2,2′-bithiophene (for P1), 4,4′-bis(2-ethylhexyl)-dithieno[3,2-b:2′,3′-d]silole (for P2), 3,3‴-didodecylquaterthiophene (for P3), 4,8-didodecylbenzo[1,2-b:4,5-b′]dithiophene (for P4), 4,8-didodecyloxybenzo[1,2-b:4,5-b′]dithiophene (for P5) and 3,3′-bis(dodecyloxy)-2,2′-bithiophene (for P6). Field-effect transistors and bulk heterojunction solar cells based on isoDPPT copolymers were fabricated and the response compared vis-a-vis to those of some DPPT-based polymers. Hole mobility (μh) of 0.03 cm2/(V·s) and solar cell power conversion efficiency (PCE) of 5.1% were achieved for polymer P2.

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