Photogenerated Charge-Aided Low-Voltage Operation of n-Channel Organic Transistors with n-Type Conjugated Polymers─Toward Photosensor Applications

Abstract

Organic semiconducting materials with a low charge carrier mobility cannot properly act as a channel layer at low voltages for organic field-effect transistors (OFETs). Here, we demonstrate that an n-type conjugated polymer, poly­[{5,5,11,11-tetrakis­(5-(2-ethylhexyl)­thiophene-2-yl)-dithieno­[2,3-d:2′,3′-d′]-s-indaceno­[1,2-b:5,6-b′]­dithiophene}-co-{2,7-bis­(2-octyldodecyl)­benzo­[lmn]­[3,8]­phenanthroline-1,3,6,8­(2H,7H)-tetraone}] (PIDTT-NDI), works as an n-channel layer at ≤5 V under light illumination, even though the devices are unable to operate as a transistor in the dark at low voltages. PIDTT-NDI layers with three different thicknesses (t = 50, 70, and 100 nm) are placed on poly­(methyl methacrylate) (PMMA) gate-insulating layers in the OFET geometry of bottom-gate and top-source/drain electrodes. Two individual monochromatic light with wavelengths (λ) of 434 and 754 nm, which are chosen from the main peaks in the optical absorption spectra of the PIDTT-NDI films, are employed as a photoexcitation source. The results show that the light illumination delivers proper output and transfer curves of typical n-channel OFETs at ≤5 V, and the electrical conductance of devices gradually increased with the light intensity. In particular, a remarkable enhancement in the photosensitivity (ca. 14,000% at λ = 434 nm) is achieved for the OFETs with the 100 nm-thick PIDTT-NDI layers due to the extremely low drain current level in the dark (5 V).

Solid-State Ionic Liquid Additive Enhances Mobility in Conjugated Polymer Field-Effect Transistors

“…Conjugated polymer (CP) semiconductors have attracted considerable interest because of their potential applications in various electronic applications such as thermoelectrics, light-emitting diodes, photovoltaic, , and field-effect transistors. − Furthermore, CPs have shown tunability of optoelectronic characteristics and solution processability, enabling their usage in deformable and large-area electronic devices . Accordingly, the charge-transport abilities and chemical stability of CPs have been extensively explored for their commercialization and corresponding devices.…”

NIR-sensing ambipolar organic phototransistors with conjugated terpolymer layers based on diketopyrrolopyrrole-benzothiadiazole-naphthalenediimide comonomer units

“…[14][15][16][17][18] To date, most OPTRs with conjugated polymers have been reported to work in a p-channel operation mode of transistors because of the channel layers consisting of p-type conjugated polymers that are relatively easy to synthesize. [19][20][21][22][23] However, n-channel mode OPTRs have been less reported owing to the relatively small number of n-type conjugated polymers that are available via synthesis. [24][25][26] Interestingly, ambipolar OPTRs, which can be operated in both p-channel and n-channel modes, have been rarely reported despite their versatility suitable for any type of semiconductor operation system.…”