Enhancement of ultraviolet light responsivity of a pentacene phototransistor by introducing photoactive molecules into a gate dielectric

Abstract

We demonstrated a new approach to fabricate an ultraviolet (UV) photodetector with a pentacene transistor structure where photoactive molecules of 6-[4′-(N,N-diphenylamino)phenyl]-3-ethoxycarbonylcoumarin (DPA-CM) were introduced into a poly(methyl methacrylate) (PMMA) gate dielectric. DPA-CM molecules strongly absorb UV light and form stable charge-separation states. When a negative gate voltage was scanned to a gate electrode of the transistor, the charge-separation states of DPA-CM molecules were converted into free electrons and holes. The free electrons traversed and subsequently reached an interface of the PMMA:DPA-CM layer and a polystyrene buffer layer, inducing accumulation of additional holes in a pentacene channel. Therefore, under 2.54 mW/cm2 of 365 nm UV irradiation, a marked increase in drain current by 6.1 × 102 times were obtained from the transistor. Moreover, the phototransistor exhibited a high light responsivity of 0.12 A/W which is about one order of magnitude larger than that of a conventional pentacene phototransistor [Lucas et al., Thin Solid Films 517, 280 (2009)]. This result will be useful for manufacturing of a high-performance UV photodetector.

Photoelectrical characteristics of UV organic thin-film transistor detectors

“…2 present the electrical characteristics of the initial photoOTFT. Regarding basic transistor device performance, the saturation-region hole mobility () is estimated by fitting the plot of the square root of drain current (I D ) versus gate voltage (V G ) with an equation [14]:…”

“…On other aspect, the absorbance of the PMMA/DPA-CM is much stronger than that of pentacene in the UV region, resulting in the DPA-CM plays an important role to construct the UV pentacene photoOTFT. The working principle was detailed in our previous report [14], here it is briefly explained. When the photoOTFT is irradiated and biased.…”

“…The photodevice exhibits a high photosensitivity or photoresponsivity and fast response characteristic. The photoOTFT was fabricated by employing the previous method [14]. The fabrication process, device structure and the properties of the main materials are shown in Fig.…”

Recent Progress in Organic Phototransistors: Semiconductor Materials, Device Structures and Optoelectronic Applications

“…On the other hand, the optoelectronic properties of organic semiconductors including photogeneration, radiative recombination or light detection can be easily tuned by changing their chemical structures . In recent years, significant research achievements in OPTs have been witnessed with the aid of a variety of organic semiconductor materials, novel device architectures and interface engineering of the devices (Figure ) …”

Improvement of Blue Organic Photodiode with Pyrazol-Derivative

“…Recently, organic optoelectronic devices, such as, organic light-emitting diodes (OLEDs) [1], organic solar cells (OSCs) [2,3], organic photodiodes (OPDs) [4,5], and organic phototransistors [6,7] have been actively studied. Because a certain organic material has a characteristic absorption spectrum, device application is expected as the specific color sensor.…”