Epoxy resin (EP) has been widely utilized in electrical equipment and electronic devices due to its fascinating electric, thermal, and mechanical properties. However, the complex insulation structures of modern power devices in high-voltage direct current systems pose several challenges for EP-based dielectrics. The most significant among these challenges is the need for EP to stably operate under greater electric fields, requiring superior breakdown strength. This paper summarizes the key factors influencing the breakdown strength of EP and reviews reported methods for enhancing this property. Recognizing the limitations of existing approaches, we propose that the emerging technology of molecule design offers a potentially optimal solution for developing EP with enhanced breakdown strength. Furthermore, we anticipate the future development direction of EP with satisfactory insulation properties. We believe that enhancing the breakdown theory of solid dielectrics, exploring new research and development methodologies, and creating environmentally friendly EP with high performance are primary focus areas. We hope that this paper will offer guidance and support for the future development of EP with superior breakdown strength, proving valuable in advancing EP-based dielectrics.

As compared with polymer semiconductors, solution-processed small-molecule semiconductors usually have poorer film-formation properties, which induces wide variations in device performance in terms of mobility and threshold voltage, thus severely limiting their commercial applications. In this work, we propose an easily accessible method to improve the performance and reduce the variability of small-molecule organic field-effect transistors (OFETs) by blending organic semiconductors with an insulator polymer, which is subsequently post-treated by gate stress to generate an electret. By blending the organic semiconductor 2, 7-didodecyl[1]benzothieno[3, 2-b][1]benzothiophene (C₁₂-BTBT) with the insulator polystyrene, uniform transport layers with vertically phase segregated morphology are obtained, from which the mobility and threshold voltage of OFETs are largely manipulated. The OFETs exhibit field-effect mobilities as high as 7.5 cm²·V^-1·s^-1 with an on/off ratio exceeding 10⁶ in ambient conditions. This double-layer structure provides an appropriate architecture for applying gate-stress to inject charges into the insulating layer, forming an electret. The generation of the electret is thermally accelerated and thus can be easily realized under moderate gate-stress at elevated temperature (e.g., 60 ℃). After cooling, the electret layer serves as a floating-gate, which not only continuously tunes the threshold voltage and field-effect mobility, but also helps minimize the contact resistances and optimize the subthreshold swing. As an application of this method, a digital inverter is built and its performance is optimized via in situ tuning of its individual transistors.