On-state performance enhancement of copolymer-based organic field effect transistors enabled by an organic metal salt dopant

Organic field effect transistors (OFETs) based on copolymers are promising for flexible and stretchable electronics, yet their large-scale application is often limited by relatively poor performance. This work demonstrates a universal and effective doping strategy employing the organic metal salt lithium tetrakis (pentafluorophenyl) borate ethyl etherate (Li-TPFPB) to significantly enhance the on-state performance of copolymer OFETs. Employing a simple solution mixing method with an optimized doping ratio (3 wt. %), multiple key device parameters are improved simultaneously without compromising the on/off ratio. This improvement is proven to be universal across different copolymer semiconductors and metal electrodes combinations. Systematic investigations reveal that the performance improvement primarily originates from a substantial reduction in trap density within the copolymer semiconductor at optimal doping ratios, which facilitates more efficient charge transport. However, excessive doping (>3 wt. %) leads to increased structural disorder and trap density, causing device degradation. This study not only identifies Li-TPFPB as an effective dopant for OFETs but also provides a comprehensive mechanistic understanding of doping ratio dependent performance, paving a simple route toward high-performance, solution-processed OFETs.