Laser-induced porous graphene films from commercial polymers

Abstract

The cost effective synthesis and patterning of carbon nanomaterials is a challenge in electronic and energy storage devices. Here we report a one-step, scalable approach for producing and patterning porous graphene films with three-dimensional networks from commercial polymer films using a CO 2 infrared laser. The sp 3 -carbon atoms are photothermally converted to sp 2 -carbon atoms by pulsed laser irradiation. The resulting laserinduced graphene (LIG) exhibits high electrical conductivity. The LIG can be readily patterned to interdigitated electrodes for in-plane microsupercapacitors with specific capacitances of 44 mF cm À 2 and power densities of B9 mWcm À 2 . Theoretical calculations partially suggest that enhanced capacitance may result from LIG's unusual ultra-polycrystalline lattice of pentagon-heptagon structures. Combined with the advantage of one-step processing of LIG in air from commercial polymer sheets, which would allow the employment of a roll-to-roll manufacturing process, this technique provides a rapid route to polymer-written electronic and energy storage devices.

Nano fabricated silicon nanorod array with titanium nitride coating for on-chip supercapacitors

“…Supercapacitor, which represents a class of electrochemical energy storage device with high power density and excellent cycling stability, has attracted tremendous interest [1416]. On-chip supercapacitor with in-plane thin film electrodes now is showing a pathway to replace microbattery utilized previously in microelectronic integrated circuits (IC) [17,18].…”

Thermal conductivity enhancement of laser induced graphene foam upon P3HT infiltration

“…It is expected (and has been confirmed by (Lin et al)) that at low laser power the foam will have the highest density and lowest porosity, but lower relative levels of graphitization; whereas at high laser power (8%-10% duty cycle) the opposite is expected (high levels of graphitization, but lower graphene ligament density and high porosity). 18 This expectation is illustrated when comparing points for the 4% and 8% duty cycles in Figure 1, where nearly identical thermal conductivity is achieved despite expected variance in density. The results of the PA measurements suggest that the 6% laser power provides an ideal medium where both graphitization and density are relatively high, resulting in peak LIG thermal conductivity.…”

“…where r is the ratio of solid ligament thermal conductivity to the polymer thermal conductivity (or fluid thermal conductivity (helium gas) is the case of no polymer infiltration) and n ¼ 2 c/H where c and H are the structural parameters determined by the foam porosity and pore diameter (further details are included in the original LIG fabrication publication's (Lin et al) supplementary material 18 ). The theoretically calculated composite thermal conductivities are illustrated by the green shaded region in Figure 3 and the measured LIG/P3HT composite thermal conductivities are indicated by the black squares and are plotted again (these are the same values from Figure 2) for comparison.…”

“…The CO 2 laser power is altered to control the degree of graphitization and resultant graphene foam thickness and porosity. 18 The entire process is performed under ambient conditions for the conversion of PI films into porous graphene foam where the porosity originates from the outgassing during the high temperature laser process. The LIG process is unique to a small class of polymers, particularly those that bear the aromatic and imide repeat units due to an overlap of the 10.6 lm CO 2 laser line with an absorbance shoulder in the PI.…”

“…18 In short, the foams are manufactured from commercially available 130 lm thick Kapton polyimide (PI) sheets using a CO 2 infrared laser where laser irradiation results in the photothermal conversion of sp 3 -carbon atoms to sp 2 -carbon atoms and the formation of a three-dimensional graphene network on the surface of the PI film. The CO 2 laser power is altered to control the degree of graphitization and resultant graphene foam thickness and porosity.…”