Binder polymer influence on the electrical and UV response of organic field-effect transistors

The use of blends of small molecule organic semiconductors (OSCs) with insulating binding polymers has been shown to be a promising route to facilitate the processing of OSCs over large areas using printing techniques. Here we fabricated organic field-effect transistors (OFETs) and phototransistors using the benchmark OSC 7-decyl-2-phenyl[1]benzothieno[3,2-b][1]benzothiophene (Ph-BTBT-10) and blends of this material with polystyrene (PS), poly(pentafluorostyrene) (PFS) and poly(methyl methacrylate) (PMMA). We show that the nature of the binding polymer has a significant impact on the device performance. The OFETs showing the best performance are the ones based on blends of PS since they reveal less interfacial traps, leading to devices with higher mobility, threshold voltage close to zero and high bias stress stability. The lowest OFET performance is found in the devices based on PMMA blends due to the higher density of majority charge carrier (i.e., holes) traps. On the other hand, regarding the response of the devices to UV light, the PFS and pristine films exhibited the highest photoresponse, which was attributed to the higher density of minority charge carrier (i.e., electrons) traps. Therefore, this work demonstrates that the binding polymer is a useful tool to optimise the OFET electrical characteristics as well as its photoresponsivity.

Automated summary

The use of blends of small molecule organic semiconductors (OSCs) with insulating binding polymers can facilitate the processing of OSCs over large areas using printing techniques. The nature of the binding polymer significantly impacts the device performance, with blends of polystyrene (PS) showing the best performance in terms of mobility, threshold voltage, and bias stress stability. On the other hand, blends with poly(methyl methacrylate) (PMMA) exhibit the lowest performance due to higher density of hole traps. For UV light response, blends with poly(pentafluorostyrene) (PFS) and pristine films demonstrate the highest photoresponse due to higher density of electron traps. The binding polymer proves to be a useful tool in optimizing the electrical characteristics and photoresponsivity of the organic field-effect transistors (OFETs).