Phase separation induced high mobility and electrical stability in organic field-effect transistors

- TIPS-pentacene and TIPS-pentacene:PS blends were explored in OFETs on Si/SiO2.
- Performance and stability enhanced due to vertical phase separation in blend OFETs.
- Maximum mobility improved from 0.2 cm2 V−1 s−1 to 2.6 cm2 V−1 s−1.
- Lesser bias-stress current decay (∼30%) in blend than neat devices (∼80%) in 2 h.
- Highly repeatable electrical characteristics in PS blend devices.

Phase separation induced high carrier mobility and electrical stability are achieved in organic field-effect transistors using TIPS-pentacene:polystyrene blends. Rigid Si/SiO2 substrate was especially chosen to explore the phase separation. A vertical phase separation between TIPS-pentacene and polystyrene as confirmed from scanning electron microscopic image, evetually leads to excellent carrier mobility in polymer blend devices compared to that of neat TIPS-pentacene. Maximum hole mobility improved from 0.2 cm2 V−1 s−1 for neat TIPS-pentacene on SiO2 to 2.6 cm2 V−1 s−1 for TIPS-pentacene blends with PS, with average value of 1.5 cm2 V−1 s−1. Apart from higher mobility, TIPS-pentacene:PS blend devices also showed much lower decay in drain current (∼30%) during a constant bias-stress of 2 h, compared to neat devices (∼80%). Interestingly, This decay was fully recovered for blend devices under rest conditions. The corresponding shift in the threshold voltage due to bias-stress was lower for TIPS-pentacene:PS device due to better quality of interface as confirmed by lower values of density of interface traps and higher trapping time. High electrical stability in TIPS-pentacene:polystyrene blend devices was also supported by repeatabiliiy studies, which exhibited nearly unchanged device characteristics.

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