Facile fabrication of conducting hollow carbon nanofibers/Si composites for copper phthalocyanine-based field effect transistors and high performance lithium-ion batteries

Abstract

In this paper, we describe the preparation and dual-use of carbon nanofibers/Si (CNFs/Si) composites as the source/drain contacts for copper phthalocyanine (CuPc) based thin film transistors (TFTs) and as anode materials for high performance lithium-ion batteries. The CNFs/Si composites are prepared by a facile chemical vapor deposition (CVD) technique with iron nitrate as the catalyst source and acetylene as the carbon source. In the CNFs/Si structure, Si particles are tightly wrapped by CNFs with an average diameter of 15–30 nm and length of 1–2 μm. It can be seen that the catalysts are grown on the top tip of the CNFs. Based on the superior properties of the CNFs coating, the CNFs/Si composites are applied in different fields. Compared with CuPc based OTFTs with Au contacts, the performances of organic thin film transistors (OTFTs) with CNFs/Si contacts are significantly improved. For OTFTs with CNFs/Si contacts, they show the on-state current increasing from 9 × 10⁻⁹ to 3 × 10⁻⁷ A at the gate voltage of −40 V, field effect mobility increasing from 1.9 × 10⁻⁴ to 4.2 × 10⁻³ cm² V⁻¹ s⁻¹, and threshold voltage shifting from 15 to 30 V for the saturation regime. These are attributed to the more effective charge-carrier injection of CNFs/Si contacts than of Au contacts. Besides, the CNFs/Si composites are also promising lithium storage host materials. They show excellent rate capability as anode materials for lithium batteries. The initial discharge and charge capacities of CNFs/Si composites at 0.05 C are 1491.6 and 1168.7 mAh g⁻¹, respectively. For comparison, the initial discharge and charge capacities of the CNFs/Si composites at 0.60 C are 1197.8 and 941.4 mAh g⁻¹, respectively. After twenty cycles, the discharge and charge capacities at 0.60 C are 834.4 and 733.9 mAh g⁻¹, respectively.