Well-Balanced Ambipolar Conjugated Polymers Featuring Mild Glass Transition Temperatures Toward High-Performance Flexible Field-Effect Transistors

Abstract

Conjugated polymers, which can be fabricated by simple processing techniques and possess excellent electrical performance, are key to the fabrication of flexible polymer field-effect transistors (PFETs) and integrated circuits. Herein, two ambipolar conjugated polymers based on (3E,7E)-3,7-bis(2-oxo-1H-pyrrolo[2,3-b]pyridin-3(2H)-ylidene)benzo[1,2-b:4,5-b′]difuran-2,6(3H,7H)-dione and dithienylbenzothiadiazole units, namely PNBDOPV-DTBT and PNBDOPV-DTF2BT, are developed. Both copolymers possess almost planar conjugated backbone conformations and suitable highest occupied molecular orbital (HOMO)/lowest unoccupied molecular orbital (LUMO) energy levels (−5.64/−4.38 eV for PNBDOPV-DTBT and −5.79/−4.48 eV for PNBDOPV-DTF2BT). Note that PNBDOPV-DTBT has a glass transition temperature (140 °C) lower than the deformation temperature of polyethylene terephthalate (PET), meaning well-ordered molecular packing can be obtained on PET substrate before its deformation in mild thermal annealing process. Flexible PFETs based on PNBDOPV-DTBT fabricated on PET substrates exhibit high and well-balanced hole/electron mobilities of 4.68/4.72 cm² V⁻¹ s⁻¹ under ambient conditions. After the further modification of Au source/drain electrodes with 1-octanethiol self-assembled monolayers, impressively high and well-balanced hole/electron mobilities up to 5.97/7.07 cm² V⁻¹ s⁻¹ are achieved in the flexible PFETs. Meanwhile, flexible complementary-like inverters based on PNBDOPV-DTBT on PET substrate also afford a much high gain of 148. The device performances of both the PFETs and inverters are among the highest values for ambipolar conjugated polymers reported to date.

Two ambipolar conjugated polymers with mild glass transition temperatures, PNBDOPV-DTBT and PNBDOPV-DTF2BT, are developed. Flexible polymer field-effect transistors (PFETs) based on PNBDOPV-DTBT fabricated on polyethylene terephthalate substrates exhibit high and well-balanced hole/electron mobilities of 5.97/7.07 cm² V⁻¹ s⁻¹ under ambient conditions. The device performance is among the best for flexible ambipolar thin film PFETs.

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