报告题目1：Rapid and non-destructive optical patterning of conjugated polymers for device applications
报告时间：2019年9月24日, 10:00-11：00
报告地点：上海大学（延长校区）平板中心会议室
报告人：Adam Moule教授
邀请人：魏斌 教授
报告人简介：
Adam J. Moulé received a Ph.D. in Physical Chemistry from the University of California, Berkeley in 2003, studying under Alex Pines. From 2004-2005 he was an Alexander von Humboldt postdoctoral scholar at the University of Cologne studying under Klaus Meerholz. Adam was an assistant professor of Chemical Engineering and Materials Science from 2007-2012 at the University of California, Davis and became a full professor of Chemical Engineering in 2019. In 2016, he won an Alexander von Humboldt sabbatical award to study at the Max Planck Institute for polymer theory. In 2017 Adam was chosen as a UC Davis chancellor’s scholar for research excellence. In 2018 he became the Joe and Essie Smith endowed chair of chemical engineering at UC Davis.
报告摘要：
A significant obstacle for the industrial development of organic electronic devices is the lack of a patterning technology having the disruptive power that photolithography exerted in traditional microelectronics. Here we present a new scalable patterning technology for organic semiconductors that takes advantage of the existing photolithography infrastructure and is compatible with digital direct-write patterning and sequential roll-to-roll (R2R) solution coating. The Moule group works on a series of solubility control techniques including the use of marginal solvents and polymer doping, that reduce the solubility of polymers at room temperature, but allow patterning at elevated temperatures. Using these techniques, we are able to vertically stack and laterally pattern mutually soluble polymer layers, which are vital processing steps needed to expand the use of organic semiconductors in device applications. Optimization of these techniques has yielded diffraction limited film patterning with regular features of 200-300 nm with only solution processing steps and direct write laser patterning. We have also recently shown that vertically patterned layers are stable, even with solvent exposure times of hours. This presentation will cover the fundamentals of optical patterning of organic semiconductors and delve into details of how to create doped microdomains, dopant diffusion, and the relationship between polymer crystallinity, dopant diffusion rate, and pattern fidelity.
报告题目2：Tomographic imaging of organic and nanoparticle photovoltaic devices
报告时间：2019年9月30日, 10:00-11：00
报告地点：上海大学（延长校区）平板中心会议室
报告人：Adam Moule教授
邀请人：魏斌 教授
报告摘要：
Since the demonstration of multiple exciton generation in Pb-chalcongenide quantum dot (QD) particles, researchers have sought to develop ordered QD arrays, called superlattice structures, in order to generate photocurrent with >100% EQE. Here we study PbSe QD superlattice arrays using electron tomography to quantify the 3D nanostructure. These QD arrays are formed by crystallization of long ligand QD’s from solution, followed by in-situ ligand exchange to produce QD arrays with short interparticle distance. The solution processing and ligand exchange introduces structural defects into the QD superlattice. We demonstrate an ability to locate the center of mass and connectivity between QDs over an array of >2500 particles. This map of diameter and connectivity between particles is an indirect measure of the local band gap, ionization energy and electron affinity. When the structural information is coupled with monticarlo simulations, we can predict how defects and grain boundaries effect charge mobility and local trapping. Thus our electron tomography characterization affords an unprecidented correlation between structure and properties at the nanoscale.
报告题目3：Measurement and modeling of molecular polymer/dopant structure and dynamics
报告时间：2019年10月10日, 10:00-11：00
报告地点：上海大学（延长校区）平板中心会议室
报告人：Adam Moule教授
邀请人：魏斌 教授
报告摘要：
Organic semiconductors (OSCs) provide the unprecedented ability to tailor properties like electronic band gap, mechanical flexibility, processability, and biocompatibility. Recent theories suggest that low frequency dynamic intra- and intermolecular motions are critical to determining localization of the charge carrier, and thus, control the hole mobility. So far, however, it has not been possible to measure intramolecular motions experimentally and therefore no unequivocal and quantitative link exists between molecular-scale thermal disorder and macroscale hole mobility in OSCs. Here we use inelastic neutron scattering (INS) to probe thermal disorder directly by measuring the high-resolution phonon spectrum in six different small molecule OSCs. Because of the virtually perfect agreement between the INS spectra and first principle simulations, we can study the coupling between hole and molecular dynamics starting from the exact knowledge of the nuclear motions in each system. This knowledge is used to generate a set of electron-phonon coupling parameters, which are used to compute hole mobility using transient localization theory. We have discovered that in some high performing materials, an important component of the non-local electron phonon coupling is carried by high frequency phonons, unlike what was previously thought. Once this element is properly taken into account the mobility, calculated from first principles, is in excellent quantitative agreement with macroscopic measurements. The analysis of the results reveal routes to improve charge mobility by engineering phonon and electron-phonon coupling.
