The instability of organic field-effect transistors (OFETs) is one key obstacle to practical application and is closely related to the unstable aggregate state of organic semiconductors (OSCs). However, the underlying reason for this instability remains unclear, and no effective solution has been developed. Herein, we find that the intrinsic tensile and compressive strains that exist in OSC films are the key origins for aggregate state instability and device degradation. We further report a strain balance strategy to stabilize the aggregate state by regulating film thickness, which is based on the unique transition from tensile strain to compressive strain with increasing film thickness. Consequently, a strain-free and ultrastable OSC film is obtained by regulating the film thickness, with which an ultrastable OFET with a five-year lifetime is realized. This work provides a deeper understanding of and a solution to the instability of OFETs and sheds light on their industrialization.

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Conductive polymers are considered promising electrode materials for organic transistors, but the reported devices with conductive polymer electrodes generally suffer from considerable contact resistance. Currently, it is still highly challenging to pattern conductive polymer electrodes on organic semiconductor surfaces with good structure and interface quality. Herein, we develop an in situ polymerization strategy to directly pattern the top-contacted polypyrrole (PPy) electrodes on hydrophobic surfaces of organic semiconductors by microchannel templates, which is also applicable on diverse hydrophobic and hydrophilic surfaces. Remarkably, a width-normalized contact resistance as low as 1.01 kΩ•cm is achieved in the PPy-contacted transistors. Both p-type and n-type organic field-effect transistors (OFETs) exhibit ideal electrical characteristics, including almost hysteresis-free, low threshold voltage, and good stability under longterm test. The facile patterning method and high device performance indicate that the in situ polymerization strategy in confined microchannels has application prospects in all-organic, transparent, and flexible electronics.

The photoelectric response of organic field-effect transistors (OFETs) will cause severe photoelectric interference, which hinders the applications of OFETs in the light environment. It is highly challenging to relieve this problem because of the high photosensitivity of most organic semiconductors. Here, we propose an efficient "exciton-polaron quenching" strategy to suppress the photoelectric response and thus construct highly photostable OFETs by utilizing a polymer electrolyte dielectricpoly(acrylic acid) (PAA). This dielectric produces high-density polarons in organic semiconductors under a gate electric field that quench the photogenerated excitons with high efficiency (∼70%). As a result, the OFETs with PAA dielectric exhibit unprecedented photostability against strong light irradiation up to 214 mW/ cm 2 , which far surpasses the reported values and solar irradiance value (∼138 mW/ cm 2 ). The strategy shows high universality in OFETs with different OSCs and electrolytes. As a demonstration, the photostable OFET can stably drive an organic light-emitting diode (OLED) under light irradiation. This work presents an efficient exciton modulation strategy in OSC and proves a high potential in practical applications.

The ORCID identification number(s) for the author(s) of this article can be found under https://doi.org/10.1002/adom.202201075.