Effect of morphological and physicochemical properties of dielectric-organic semiconductor interfaces on photoresponse of organic phototransistors

Enhanced Optical Switching Characteristics of Organic Phototransistor by Adopting Photo-Responsive Polymer in Hybrid Gate-Insulator Configuration

“…To investigate the effects of the hybrid gate insulator configuration on the UV-sensing properties of the p-OPTs, we fabricated two types of devices with different polymer gate insulators (i.e., one type has a single-polymer gate insulator consisting of PMMA, whereas the other type has a hybrid gate insulator consisting of PVP/PMMA as shown in Figure 1a,b, respectively). Since the OSC/gate insulator interface plays a critical role in determining the photoresponsive characteristics of p-OPTs (i.e., the optical switching and memory properties), there have been numerous studies on how to regulate the characteristics of the device by modifying the interface between the OSC and gate insulator [17,18,[21][22][23][24][25][26][27]. Specifically, PMMA-based p-OPTs have been reported as promising candidates for photo-switching devices because there are no trapping sites at the OSC/gate insulator interface, as shown in the left panel of Figure 1c [17].…”

“…To compare the photoresponse of two types of OPTs (i.e., an OPT with a single PMMA layer as a gate insulator, and an OPT with a PVP/PMMA hybrid layer as a gate insulator), two different devices were fabricated as shown in Figure 1a,b. To obtain similar drain levels (electrical characteristics) of both devices, these two types of gate insulators were designed to have different thicknesses, because PMMA and PVP have different dielectric constant (k) values of 3.5 and 4.5, respectively [17]. It should be noted that drain current is related with capacitance per unit area which is proportional to dielectric constant and inversely proportional to thickness of a gate insulator.…”

“…To construct the photoresponsive layer, the UV-responsive material poly(4-vinylphenol) (PVP) was used. A layer of PVP is suitable as a p-OPT gate insulator because it affords excellent optical and dielectric properties [15][16][17][18][19][20]. However, in such devices, the hydroxyl groups of PVP that act as electron trap sites at the interface between an organic semiconductor (OSC) and a gate insulator inherently limit the optical switching performance [17,18].…”

“…A layer of PVP is suitable as a p-OPT gate insulator because it affords excellent optical and dielectric properties [15][16][17][18][19][20]. However, in such devices, the hydroxyl groups of PVP that act as electron trap sites at the interface between an organic semiconductor (OSC) and a gate insulator inherently limit the optical switching performance [17,18]. We implemented poly(methyl methacrylate) (PMMA) film as the interfacial layer adjacent to the OSC to ensure that the device has reliable optical switching capability, because PMMA has no functional groups for photogenerated minority carriers [17].…”

“…However, in such devices, the hydroxyl groups of PVP that act as electron trap sites at the interface between an organic semiconductor (OSC) and a gate insulator inherently limit the optical switching performance [17,18]. We implemented poly(methyl methacrylate) (PMMA) film as the interfacial layer adjacent to the OSC to ensure that the device has reliable optical switching capability, because PMMA has no functional groups for photogenerated minority carriers [17]. Our p-OPT, which has a hybrid gate insulator, exhibited stable UV sensing characteristics, and demonstrated better photosensitivity and photoresponsivity than its conventional counterpart (an OPT with a single-polymer PMMA gate insulator).…”