Establishing efficient electrical contact to the weak crystals of triethylsilylethynyl anthradithiophene

Triethylsilylethynyl anthradithiophene (TES ADT) forms weak van der Waals crystals in the solid state because its bulky TES side groups limit intermolecular interactions. Consequently, TES ADT melts easily and locally when it experiences heat conduction from the metal evaporation process to form electrical contacts. The performance of TES ADT thin-film transistors is thus highly dependent upon the manner in which electrical contacts are established to the organic semiconductor. Bottom-contact TES ADT thin-film transistors in which the electrodes are fabricated prior to the organic semiconductor deposition routinely exhibit a charge-carrier mobility of 0.11 ±0.05 cm ²/V·s. Top-contact thin-film transistors with electrodes patterned directly on top of TES ADT by metal evaporation through a shadow mask, on the other hand, exhibit highly variable device characteristics with a charge-carrier mobility 0.03 ±0.03 cm ²/V·s. To avoid thermal damage to TES ADT during electrode fabrication, we separately defined gold source and drain electrodes on elastomeric stamps and then laminated the electrodes against TES ADT to form top-contact devices. These laminated top-contact thin-film transistors exhibit device characteristics with minimal current - voltage hysteresis and an enhanced charge-carrier mobility of 0.19 ±0.06 cm ²/ V·s.