Review of recent advances and sensing mechanisms in solid-state organic thin-film transistor (OTFT) sensors

Organic thin-film transistors (OTFTs) have shown great potential as chemical and biological sensors for applications in environmental monitoring and diagnostics with high sensitivities and part-per-billion molar concentration limits of detection. Sensitivity and selectivity of OTFT sensors has been further enhanced by advances in semiconductor processing both by thermal evaporation and solution processing, enabling precise control of thin-film texture and structures. In addition to semiconductor processing, pre- and post-deposition techniques including interfacial engineering through surface chemistry, solvent vapour annealing and fabrication of porous structures have become attractive pathways towards improving sensor performance. This review discusses recent progress in solid-state OTFT sensors and strategies for improving their sensitivity, selectivity, and detection limit. Topics addressed in this review include structure-property relationships of OTFT sensors and different sensing mechanisms such as oxidative and reductive analyte-semiconductor interactions, semiconductor recrystallization by volatile organic compound exposure, and biomolecules reacting with functional groups on the electrodes or semiconductors. Finally, the review covers advances in OTFT fabrication and thin-film processing techniques which improve performance, biocompatibility and sustainability of resulting solid-state sensors. Advances in processing of active layers of organic thin-film transistor (OTFT)-based chemical and biological sensors have enabled significant developments in their performance, achieving part-per-billion molar concentration limits of detection.