Flexible Organic Thin Film Transistors Incorporating a Biodegradable CO2-Based Polymer as the Substrate and Dielectric Material

Cut Rullyani,Chao-Feng Sung,Chih-Wei Chu,Hong-Cheu Lin

doi:10.1038/s41598-018-26585-0

Abstract

Employing CO2-based polymer in electronic applications should boost the consumption of CO2 feedstocks and provide the potential for non-permanent CO2 storage. In this study, polypropylene carbonate (PPC) is utilized as a dielectric and substrate material for organic thin film transistors (OTFTs) and organic inverter. The PPC dielectric film exhibits a surface energy of 47 mN m−1, a dielectric constant of 3, a leakage current density of less than 10−6 A cm−2, and excellent compatibility with pentacene and PTCDI-C8 organic semiconductors. Bottom-gate top-contact OTFTs are fabricated using PPC as a dielectric; they exhibits good electrical performance at an operating voltage of 60 V, with electron and hole mobilities of 0.14 and 0.026 cm2 V−1 s−1, and on-to-off ratios of 105 and 103, respectively. The fabricated p- and n-type transistors were connected to form a complementary inverter that operated at supply voltages of 20 V with high and low noise margins of 85 and 69%, respectively. The suitability of PPC as a substrate is demonstrated through the preparation of PPC sheets by casting method. The fabricated PPC sheets has a transparency of 92% and acceptable mechanical properties, yet they biodegraded rapidly through enzymatic degradation when using the lipase from Rhizhopus oryzae.

Highlights

Interest in the use of CO2 as a raw material for chemical synthesis is growing; CO2 is abundant, inexpensive, non-flammable and renewable
Pellets and its chemical structure; (ii) polypropylene carbonate (PPC) dissolved in EtOAc; (iii) the solution is poured into a Petri dish and baked for 4 h; (iv) a 10 × 10 cm transparent PPC substrate; (v) organic thin film transistors (OTFTs) device fabricated on the PPC substrate. (b) Transmittance spectrum of a 90-μm-thick PPC substrate. (c) Stress–strain curve obtained from tensile tests of PPC strips
The solid PPC pellets were dissolved in ethyl acetate (EtOAc); the solution was cast into a 4-inch Petri dish and baked to evaporate the solvent

Summary

Introduction

Interest in the use of CO2 as a raw material for chemical synthesis is growing; CO2 is abundant, inexpensive, non-flammable and renewable. One of the material products prepared from CO2 is polypropylene carbonate (PPC), a biodegradable aliphatic polyester synthesized from the copolymerization of CO2 and propylene oxide (PO) using a zinc complex as the catalyst[5,6]. PPC can be tailored for applications with a broad range of material characteristics—from solid plastics to soft, flexible foams—depending on the length of the polymer chains. It can be foamed and processed into thin films, and it readily mixes with other biopolymers[9,10] or added organic/inorganic fillers[11,12] to alter the thermal and mechanical properties. Our study has validated the reliability of PPC as a dielectric and substrate material for environmentally friendly thin film transistors

Methods

Results

Conclusion