High T_g Cyclic Olefin Copolymer Gate Dielectrics for N,N′‐Ditridecyl Perylene Diimide Based Field‐Effect Transistors: Improving Performance and Stability with Thermal Treatment

Abstract

A novel application of ethylene‐norbornene cyclic olefin copolymers (COC) as gate dielectric layers in organic field‐effect transistors (OFETs) that require thermal annealing as a strategy for improving the OFET performance and stability is reported. The thermally‐treated N,N′‐ditridecyl perylene diimide (PTCDI‐C13)‐based n‐type FETs using a COC/SiO2 gate dielectric show remarkably enhanced atmospheric performance and stability. The COC gate dielectric layer displays a hydrophobic surface (water contact angle = 95° ± 1°) and high thermal stability (glass transition temperature = 181 °C) without producing crosslinking. After thermal annealing, the crystallinity improves and the grain size of PTCDI‐C13 domains grown on the COC/SiO2 gate dielectric increases significantly. The resulting n‐type FETs exhibit high atmospheric field‐effect mobilities, up to 0.90 cm2 V−1 s−1 in the 20 V saturation regime and long‐term stability with respect to H2O/O2 degradation, hysteresis, or sweep‐stress over 110 days. By integrating the n‐type FETs with p‐type pentacene‐based FETs in a single device, high performance organic complementary inverters that exhibit high gain (exceeding 45 in ambient air) are realized.

Photo-patternable high-k ZrOx dielectrics prepared using zirconium acrylate for low-voltage-operating organic complementary inverters

“…5a illustrates the AFM images and height profiles of pentacene and PTCDI-C13 thin films grown on COC and ZrO x dielectric layers, respectively. Surface morphologies of both the pentacene and PTCDI-C13 are in good agreement with previous reports where those organic semiconductors were grown on COC surfaces [29,40]. Pentacene thin films deposited on the COC surface exhibited large grains with sizes !1 mm and PTCDI-C13 molecules formed large and flat grains on a COC surface after thermal annealing at 120 C. The cross-sectional height profile of the PTCDI-C13 thin films revealed that the height of each layer was about 26.2 Å, corresponding to the d-spacing of the PTCDI-C13 molecules along the out-of-plane direction, as will be further discussed.…”

“…Thermally annealed PTCDI-C13 thin films grown on a COC/ZrO x dielectric surface exhibited [00l] out-of-plane reflections that correspond to a d- spacing of 26.4 Å, which agrees well with the results from AFM analysis. In addition, the PTCDI-C13 thin films exhibited many strong reflections along the q z axis at given q xy positions, which means that PTCDI-C13 crystals formed three-dimensional multilayered structures [29,40,43]. All of these results strongly suggest that both the pentacene and PTCDI-C13 molecules were grown on COC/ZrO x dielectric surfaces with favorable crystalline structures for efficient charge transport in OFETs, similar to previous reports of hydrophobic SAM or polymeric surfaces [26,29,40,42e44].…”

“…These stable low-voltage operations of the OFETs, despite ultrathin dielectric thickness, originated from good insulating properties and high capacitances of ZrO x layers and the hydroxyl-free nature of COC. The hydroxyl-free COC surface prevents the adsorption of H 2 O and O 2 at the semiconductor/dielectric interface, thereby minimizing charge carrier traps in the FET channel [40,42,43]. Based on the pentacene and PTCDI-C13 OFETs, we fabricated organic complementary inverters using COC/ZrO x dielectrics.…”

“…Before their deposition, the surface of the ZrO x was modified with an ultrathin hydrophobic COC film to enhance the performance and stability of the OFETs [29,33,40]. We used COC with a high glass transition temperature (T g of~180 C) to guarantee thermal stability during thermal annealing of PTCDI-C13 [40,41]. Surface modification with COC films effectively smoothed the surface of ZrO x , as we can see a lowered root-mean-square roughness (r.m.s.)…”

Ultrathin Air-Stable n-Type Organic Phototransistor Array for Conformal Optoelectronics

“…From the view of molecular design, PTCDI-C 13 H 27 is one of perylene derivatives that is favorable for the good stability in n -type organic transistors 20,26 . At the same time, PMMA is used as the dielectric of the transistor because its hydrophobic nature has been extensively shown to be favorable for good device stability 27,28 .…”