Enhancement of Interfacial Thermal Transport between Metal and Organic Semiconductor Using Self-Assembled Monolayers with Different Terminal Groups
HZ Fan and M Wang and D Han and JZ Zhang and JC Zhang and XY Wang, JOURNAL OF PHYSICAL CHEMISTRY C, 124, 16748-16757 (2020).
Inferior heat transfer between metal and organic semiconductor is a challenge for the performance improvement of organic semiconductor devices. In this paper, we use nonequilibrium molecular dynamics to study the thermal energy transport between functionalized gold (Au) and pentacene interfaces. The functionalized modifications of the Au surface are implemented by inserting four different self-assembled monolayers (SAMs) at the interface of Au and pentacene. The four different SAMs include 1-hexanethiol HS(CH2)(5)CH3, 6-aminohexane-1-thiol HS(CH2)(6)NH2, 6-mercapto-1-hexanol HS(CH2)(6)OH, and 6-mercaptohexanoic acid HS(CH2)(5)COOH. The interfacial thermal conductance of the bare Au interface is 8.91 +/- 2.45 MW m(-2) K-1. It is found that the interfacial thermal conductance can be enhanced by all four SAMs. The SAMs HS(CH2)(5)CH3 and HS(CH2)(6)NH2 with a similar enhancement ability improve the interfacial thermal conductance about six to seven times. Moreover, the SAMs with stronger polarization groups HS(CH2)(6)OH and HS(CH2)(5)COOH display larger enhancement ability. Especially, the interfacial thermal conductance of the SAM HS(CH2)(5)COOH-functionalized Au interface is increased about 11 times. The enhancement of interfacial thermal transport is attributed to the better phonon vibrational coupling and the stronger interfacial interactions. SAMs can play the role of a "phonon bridge" to connect the phonon density of states of Au and pentacene, which leads to the increase in interfacial thermal conductance at the interface. The stronger polarization groups of SAMs bring about the higher adhesion energy and pull interfacial atoms closer to the interface, which leads to smaller temperature drops and higher interfacial thermal conductance. The existences of hydrogen bonds are also observed for SAMs HS(CH2)(6)OH and HS(CH2)(5)COOH-functionalized interfaces, which are beneficial to the energy transfer at the interface. This work can provide a significant insight into tuning thermal transport properties of organic electronic devices.
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