Hierarchically Porous, Laser-Pyrolyzed Carbon Electrode from Black Photoresist for On-Chip Microsupercapacitors.

Soongeun Kwon,Geehong Kim,Hyungjun Lim,Jaejong Lee,Hyung Cheoul Shim,Junhyoung Ahn,Hak-Jong Choi,Kee-Bong Choi,Yeoheung Yoon

doi:10.3390/nano11112828

Abstract

We report a laser-pyrolyzed carbon (LPC) electrode prepared from a black photoresist for an on-chip microsupercapacitor (MSC). An interdigitated LPC electrode was fabricated by direct laser writing using a high-power carbon dioxide (CO2) laser to simultaneously carbonize and pattern a spin-coated black SU-8 film. Due to the high absorption of carbon blacks in black SU-8, the laser-irradiated SU-8 surface was directly exfoliated and carbonized by a fast photo-thermal reaction. Facile laser pyrolysis of black SU-8 provides a hierarchically macroporous, graphitic carbon structure with fewer defects (ID/IG = 0.19). The experimental conditions of CO2 direct laser writing were optimized to fabricate high-quality LPCs for MSC electrodes with low sheet resistance and good porosity. A typical MSC based on an LPC electrode showed a large areal capacitance of 1.26 mF cm−2 at a scan rate of 5 mV/s, outperforming most MSCs based on thermally pyrolyzed carbon. In addition, the results revealed that the high-resolution electrode pattern in the same footprint as that of the LPC-MSCs significantly affected the rate performance of the MSCs. Consequently, the proposed laser pyrolysis technique using black SU-8 provided simple and facile fabrication of porous, graphitic carbon electrodes for high-performance on-chip MSCs without high-temperature thermal pyrolysis.

Highlights

On-chip microsupercapacitors (MSCs) have received great interest as miniaturized power sources due to their compact size, high power, and long life cycle characteristics as supercapacitors (SCs) with micron-scale electrode dimensions [1,2,3]
The carbon black materials in black SU-8 acted as optical absorbers
We investigated the effect of the laser irradiation conditions on the graphitic structures of the laser-pyrolyzed carbon (LPC) films (Figure S3)

Summary

Introduction

On-chip microsupercapacitors (MSCs) have received great interest as miniaturized power sources due to their compact size, high power, and long life cycle characteristics as supercapacitors (SCs) with micron-scale electrode dimensions [1,2,3]. Carbon nanomaterials (such as carbon nanotubes [7], graphene [8], and MXene [9]) have attracted tremendous interest as high-performance on-chip MSCs electrode materials due to their large surface area and high electrical conductivity. These materials require a costly and complicated material preparation process, such as hightemperature synthesis, material purification, and dispersion in toxic solvents for further processing [7,8,9]. As conventional photoresists show an electrically insulating property, a thermal annealing process

Methods

Results

Conclusion