Direct Effect of Dielectric Surface Energy on Carrier Transport in Organic Field-Effect Transistors

Abstract

The understanding of the characteristics of gate dielectric that leads to optimized carrier transport remains controversial, and the conventional studies applied organic semiconductor thin films, which introduces the effect of dielectric on the growth of the deposited semiconductor thin films and hence only can explore the indirect effects. Here, we introduce pregrown organic single crystals to eliminate the indirect effect (semiconductor growth) in the conventional studies and to undertake an investigation of the direct effect of dielectric on carrier transport. It is shown that the matching of the polar and dispersive components of surface energy between semiconductor and dielectric is favorable for higher mobility. This new empirical finding may show the direct relationship between dielectric and carrier transport for the optimized mobility of organic field-effect transistors and hence show a promising potential for the development of next-generation high-performance organic electronic devices.

Dielectric Selection for Solution‐Processed High‐Mobility TIPS‐Pentacene Microwire Field‐Effect Transistors

“…By comparing the results of the optical microscopy and AFM with the mobilities, we experimentally confirm that the dominant fact for mobility change of the solution‐processed TIPS‐pentacene single‐crystal microwire arrays on the different dielectrics should not be ascribed to the morphology of the semiconductor layer. Further, to explore the direct interaction between dielectric and organic semiconductors, we compared the mobility and the surface characteristics of gate dielectric layers that possibly affect mobility, including surface roughness, polarity, total surface energy, and polar and disperse components of surface energy …”

“…This experiment conclusion for in situ grown TIPS‐pentacene via solution process is well consistent with our previous report on pregrown single‐crystal devices . In our previous report, PH5T2, pentacene, and zinc phthalocyanine (ZnPc) single crystals were grown by a vapor‐transport process, and then were mechanically transferred onto the target dielectrics for fabrication of OFETs.…”

“…For SiO 2 and OTS/SiO 2 , one of two components of their surface energy shows the dramatic difference with that of TIPS‐pentacene, which possibly explains the low mobility on SiO 2 and OTS/SiO 2 dielectrics. Therefore, our experiments show that the polar and dispersive components jointly affect the mobility of the solution‐processed TIPS‐pentacene single‐crystal microwire OFETs, which is ascribed to the weak interface tension and low‐density traps for the matched components of surface energy between semiconductor and dielectric …”

“…Recently, our group also mechanically transferred the vapor‐grown Ph5T2 organic single crystals onto the target dielectrics. The device difference induced by the single crystal size were first removed by the statistical data, and the mobility difference on the different dielectric was ascribed to the matched polar and disperse components of surface energy between dielectric and semiconductor …”

Understanding, Optimizing, and Utilizing Nonideal Transistors Based on Organic or Organic Hybrid Semiconductors

“…The highest mobility is reached when both components of the surface energy of the dielectric are close to the corresponding value of Ph5T2. Reproduced with permission . Copyright 2018, American Chemical Society.…”