High-throughput Molecular Simulations into the Morphology of P3HT:PCBM Blends

The goal of this research is to understand how temperature, solvent quality, solvent amount, and the concentrations of organic photovoltaic (OPV) components determine active layer morphology. This understanding will improve techniques for engineering OPV devices, which can be inexpensively processed from abundant materials but presently suffer from low photoconversion efficiencies. We perform molecular dynamics (MD) simulations using HOOMD-Blue accelerated with graphics processing units (GPUs) to quantify how individual molecules self-assemble into structures that influence power conversion efficiency. We simulate blends of poly(3-hexylthiophene-2,5-diyl) (P3HT) with [6,6]-phenyl-C61-butyric acid methyl ester (PC61BM) and [6,6]-phenyl-C71-butyric acid methyl ester (PC71BM), three of the most important molecules in OPVs. By screening hundreds of combinations of concentration, temperature, and solvent properties, we can identify the conditions that optimize their self-organization. We quantify the degree of order in the predicted morphologies with radial distribution functions, structure factors, and simulated diffraction patterns. We find morphologies in agreement with prior experimental and theoretical work, and offer suggestions for future combinatorial studies

Molecular Simulations for Organic Photovoltaic Self-Assembly

The goal of this project is to help experimentalists choose ingredients and conditions for synthesizing solar cells made with organic molecules.The packing of molecules in organic photovoltaics (OPVs) influences charge transport and overall solar cell efficiency. We use molecular dynamics (MD) simulations to predict equilibrium morphologies of new candidate OPV ingredients. We develop new software in python for initializing, simulating, and analyzing these new compounds. The MD simulations provide predictions of molecular structure that can be used to infer model correctness and electronic properties. Optimal conditions for the self-assembly of ordered systems of ITIC and derivatives are identified. Conditions of interest for self assembly include temperatures around 300 K and densities in the range of 0.9 to 1.1. Overall we find the new models we create of ITIC, ITIC-F4, and CZTPTZ8FITIC to show promise in predicting structure of experimentally-relevant length scales and time scales, which should help to inform how charges move through materials made with these new organic semiconductors

Molecular Simulations of Organic Semiconductors for Clean Energy Production

Energy can be produced more sustainably through both the creation of new sustainable solar technologies and by lowering the impact of fossil fuels use. In this work, we simulate asphaltenes, which could be used as an ingredient in organic photovoltaics (OPVs) and which also clogs oil pipelines. OPVs are composed of organic semiconductor materials making them lightweight, flexible, and easy to manufacture. The same materials used in OPVs offer promise in a wide range of applications including organic field effect transistors (OFETs) and organic light emitting diodes (OLEDs). The asphaltenes simulated here are polydisperse aromatic molecules found as solid aggregates in petroleum refineries. We simulate the controlled aggregation of asphaltenes with varying aromatic core sizes and varying tail amounts and find they assemble long, slightly symmetrical chains. These chains are beneficial for electron mobility, a good thing for efficient organic solar cells. This work demonstrates the potential to use the waste from one energy production method (oil refining) as an ingredient for solar energy production