Thermal transport in amorphous small organic materials: a mechanistic study.

Understanding the thermal transport mechanisms in amorphous organic materials is of great importance to solve hot-spot issues in organic-electronics nanodevices. Here we studied thermal transport in two popular molecular electronic materials, N,N-dicarbazolyl-3,5-benzene (mCP) and N,N'-diphenyl-N,N'-di(3-methylphenyl)-(1,1'-biphenyl)-4,4'diamine (TPD), in the amorphous state by molecular dynamics simulations. We found that due to the softness of organic materials, the low thermal conductivity of both systems can be greatly enhanced under pressure. Notably, in such systems, the convective term of heat flux provides an important contribution to thermal transport as it cross-correlates with the Virial term in the Green-Kubo formula. Mode diffusivity calculations reveal that low-frequency modes can contribute significantly to thermal transport in both mCP and TPD. By increasing the pressure, the sound velocity and relaxation time of such low-frequency modes can be enhanced, and a part of these modes converts from diffusons to propagons. The cooperation of these three effects is responsible for the strong pressure dependence of thermal transport in amorphous organic systems. Molecular pair heat flux calculations demonstrate that heat transfer mainly happens between pairs of molecules with distances below 1.4 nm. This work paves the way for the optimization of thermal transport in amorphous organic materials widely used in opto-electronics, e.g. as OLED and OPV.

[1]  Yu Zhao,et al.  Thermal Transport Engineering in Graphdiyne and Graphdiyne Nanoribbons , 2019, ACS omega.

[2]  Xiaoliang Zhang,et al.  Thermal transport crossover from crystalline to partial-crystalline partial-liquid state , 2018, Nature Communications.

[3]  Yingjun Liu,et al.  Chemically doped macroscopic graphene fibers with significantly enhanced thermoelectric properties , 2018, Nano Research.

[4]  Zhan Peng,et al.  Thermal Transport in Soft PAAm Hydrogels , 2017, Polymers.

[5]  D. Donadio,et al.  Native surface oxide turns alloyed silicon membranes into nanophononic metamaterials with ultralow thermal conductivity , 2017, 1705.03143.

[6]  Y. Yue,et al.  A Review of Thermal Transport in Low-Dimensional Materials Under External Perturbation: Effect of Strain, Substrate, and Clustering , 2017 .

[7]  Yue Chen,et al.  Molecular dynamics study of thermal transport in a dinaphtho[2,3-b:2',3'-f]thieno[3,2-b]thiophene (DNTT) organic semiconductor. , 2017, Nanoscale.

[8]  Renkun Chen,et al.  Thermal transport in amorphous materials: a review , 2016 .

[9]  Yingjun Liu,et al.  Systematic characterization of transport and thermoelectric properties of a macroscopic graphene fiber , 2016, Nano Research.

[10]  D. Donadio,et al.  Blocking Phonon Transport by Structural Resonances in Alloy-Based Nanophononic Metamaterials Leads to Ultralow Thermal Conductivity. , 2016, Physical review letters.

[11]  A. McGaughey,et al.  Vibrational mean free paths and thermal conductivity of amorphous silicon from non-equilibrium molecular dynamics simulations , 2016, 1605.08925.

[12]  T. Zhu,et al.  Generalized Debye-Peierls/Allen-Feldman model for the lattice thermal conductivity of low-dimensional and disordered materials , 2016, 1602.02419.

[13]  W. Soboyejo,et al.  Pressure-assisted fabrication of organic light emitting diodes with MoO3 hole-injection layer materials , 2014 .

[14]  J. Oksanen,et al.  Role of anharmonic phonon scattering in the spectrally decomposed thermal conductance at planar interfaces , 2014, 1405.3868.

[15]  A. McGaughey,et al.  Thermal conductivity accumulation in amorphous silica and amorphous silicon , 2014 .

[16]  A. Balandin.  Thermal properties of graphene and nanostructured carbon materials. , 2011, Nature materials.

[17]  Donald B. Hondongwa,et al.  Ultrasonic attenuation in amorphous silicon at 50 and 100 GHz , 2011 .

[18]  Mengqiu Long,et al.  Anisotropic Thermal Transport in Organic Molecular Crystals from Nonequilibrium Molecular Dynamics Simulations , 2011 .

[19]  Gang Chen,et al.  Polyethylene nanofibres with very high thermal conductivities. , 2010, Nature nanotechnology.

[20]  Giulia Galli,et al.  Atomistic simulations of heat transport in silicon nanowires. , 2009, Physical review letters.

[21]  Gang Chen,et al.  High thermal conductivity of single polyethylene chains using molecular dynamics simulations. , 2008, Physical review letters.

[22]  A. Dhar.  Heat transport in low-dimensional systems , 2008, 0808.3256.

[23]  Ali Shakouri,et al.  Nanoscale Thermal Transport and Microrefrigerators on a Chip , 2006, Proceedings of the IEEE.

[24]  E. Pop,et al.  Thermal conductance of an individual single-wall carbon nanotube above room temperature. , 2005, Nano letters.

[25]  B. Kippelen,et al.  Thermal transport properties of thin films of small molecule organic semiconductors , 2005 .

[26]  L. H. Sperling,et al.  Introduction to Physical Polymer Science: Sperling/Introduction to Physical Polymer Science, Fourth Edition , 2005 .

[27]  Stephen R. Forrest,et al.  The path to ubiquitous and low-cost organic electronic appliances on plastic , 2004, Nature.

[28]  A. Politi,et al.  Thermal conduction in classical low-dimensional lattices , 2001, cond-mat/0112193.

[29]  S. Taraskin,et al.  Determination of the Ioffe-Regel limit for vibrational excitations in disordered materials , 1999 .

[30]  P. B. Allen,et al.  NUMERICAL STUDY OF LOW-FREQUENCY VIBRATIONS IN AMORPHOUS SILICON , 1999 .

[31]  W. L. Jorgensen,et al.  Development and Testing of the OPLS All-Atom Force Field on Conformational Energetics and Properties of Organic Liquids , 1996 .

[32]  C. P. Buckley,et al.  Introduction to physical polymer science , 1993 .

[33]  Allen,et al.  Thermal conductivity of disordered harmonic solids. , 1993, Physical review. B, Condensed matter.

[34]  Steve Plimpton,et al.  Fast parallel algorithms for short-range molecular dynamics , 1993 .

[35]  S. Nosé.  A unified formulation of the constant temperature molecular dynamics methods , 1984 .

[36]  J. M. Dickey,et al.  Computer Simulation of the Lattice Dynamics of Solids , 1969 .

[37]  M. G. Holland.  Analysis of Lattice Thermal Conductivity , 1963 .

[38]  J. Callaway.  Model for Lattice Thermal Conductivity at Low Temperatures , 1959 .

[39]  R. Kubo.  Statistical-Mechanical Theory of Irreversible Processes : I. General Theory and Simple Applications to Magnetic and Conduction Problems , 1957 .

[40]  Melville S. Green,et al.  Markoff Random Processes and the Statistical Mechanics of Time‐Dependent Phenomena. II. Irreversible Processes in Fluids , 1954 .