6 research outputs found
A Bayesian Approach to Predict Solubility Parameters
Solubility is a ubiquitous phenomenon in many aspects of material science. While solubility can be determined by considering the cohesive forces in a liquid via the Hansen solubility parameters (HSP), quantitative structure-property relationship models are often used for prediction, notably due to their low computational cost. Herein, we report gpHSP, an interpretable and versatile probabilistic approach to determining HSP. Our model is based on Gaussian processes (GP), a Bayesian machine learning approach that provides uncertainty bounds to prediction. gpHSP achieves its flexibility by leveraging a variety of input data, such as SMILES strings, COSMOtherm simulations, and quantum chemistry calculations. gpHSP is built on experimentally determined HSP, including a general solvents set aggregated from literature, and a polymer set experimentally characterized by this group of authors. In all sets, we obtained a high degree of agreement, surpassing well-established machine learning methods. We demonstrate the general applicability of gpHSP to miscibility of organic semiconductors, drug compounds and in general solvents, which can be further extended to other domains. gpHSP is a fast and accurate toolbox, which could be applied to molecular design for solution processing technologies.<br
Understanding and controlling the evolution of nanomorphology and crystallinity of organic bulk-heterojunction blends with solvent vapor annealing
Solvent vapor annealing (SVA) has been shown to significantly improve the device performance of organic bulk-heterojunction solar cells, yet the mechanisms linking nanomorphology, crystallinity of the active layer, and performance are still largely missing. Here, the mechanisms are tackled by correlating the evolution of nanomorphology, crystallinity, and performance with advanced transmission electron microscopy methods systematically. Model system of DRCN5T:PC71BM blends are SVA treated with four solvents differing in their donor and acceptor solubilities. The choice of solvent drastically influences the rate at which the maximum device efficiency establishes, though similar values can be achieved for all solvents. The donor solubility is identified as a key parameter that controls the kinetics of diffusion and crystallization of the blend molecules, resulting in an inverse relationship between optimal annealing time and donor solubility. For the highest efficiency, optimum domain size and single-crystalline nature of DRCN5T fibers are found to be crucial. Moreover, the π–π stacking orientation of the crystallites is directly revealed and related to the nanomorphology, providing insight into the charge carrier transport pathways. Finally, a qualitative model relating morphology, crystallinity, and device efficiency evolution during SVA is presented, which may be transferred to other light-harvesting blends.</p
Robot-Based High-Throughput Engineering of Alcoholic Polymer: Fullerene Nanoparticle Inks for an Eco-Friendly Processing of Organic Solar Cells
Development
of high-quality organic nanoparticle inks is a significant scientific
challenge for the industrial production of solution-processed organic
photovoltaics (OPVs) with eco-friendly processing methods. In this
work, we demonstrate a novel, robot-based, high-throughput procedure
performing automatic poly(3-hexylthio-phene-2,5-diyl) and indene-C<sub>60</sub> bisadduct nanoparticle ink synthesis in nontoxic alcohols.
A novel methodology to prepare particle dispersions for fully functional
OPVs by manipulating the particle size and solvent system was studied
in detail. The ethanol dispersion with a particle diameter of around
80–100 nm exhibits reduced degradation, yielding a power conversion
efficiency of 4.52%, which is the highest performance reported so
far for water/alcohol-processed OPV devices. By successfully deploying
the high-throughput robot-based approach for an organic nanoparticle
ink preparation, we believe that the findings demonstrated in this
work will trigger more research interest and effort on eco-friendly
industrial production of OPVs
Robot-Based High-Throughput Engineering of Alcoholic Polymer: Fullerene Nanoparticle Inks for an Eco-Friendly Processing of Organic Solar Cells
Development
of high-quality organic nanoparticle inks is a significant scientific
challenge for the industrial production of solution-processed organic
photovoltaics (OPVs) with eco-friendly processing methods. In this
work, we demonstrate a novel, robot-based, high-throughput procedure
performing automatic poly(3-hexylthio-phene-2,5-diyl) and indene-C<sub>60</sub> bisadduct nanoparticle ink synthesis in nontoxic alcohols.
A novel methodology to prepare particle dispersions for fully functional
OPVs by manipulating the particle size and solvent system was studied
in detail. The ethanol dispersion with a particle diameter of around
80–100 nm exhibits reduced degradation, yielding a power conversion
efficiency of 4.52%, which is the highest performance reported so
far for water/alcohol-processed OPV devices. By successfully deploying
the high-throughput robot-based approach for an organic nanoparticle
ink preparation, we believe that the findings demonstrated in this
work will trigger more research interest and effort on eco-friendly
industrial production of OPVs
Combined Computational Approach Based on Density Functional Theory and Artificial Neural Networks for Predicting The Solubility Parameters of Fullerenes
The solubility of organic semiconductors
in environmentally benign
solvents is an important prerequisite for the widespread adoption
of organic electronic appliances. Solubility can be determined by
considering the cohesive forces in a liquid via Hansen solubility
parameters (HSP). We report a numerical approach to determine the
HSP of fullerenes using a mathematical tool based on artificial neural
networks (ANN). ANN transforms the molecular surface charge density
distribution (σ-profile) as determined by density functional
theory (DFT) calculations within the framework of a continuum solvation
model into solubility parameters. We validate our model with experimentally
determined HSP of the fullerenes C<sub>60</sub>, PC<sub>61</sub>BM,
bisPC<sub>61</sub>BM, ICMA, ICBA, and PC<sub>71</sub>BM and through
comparison with previously reported molecular dynamics calculations.
Most excitingly, the ANN is able to correctly predict the dispersive
contributions to the solubility parameters of the fullerenes although
no explicit information on the van der Waals forces is present in
the σ-profile. The presented theoretical DFT calculation in
combination with the ANN mathematical tool can be easily extended
to other π-conjugated, electronic material classes and offers
a fast and reliable toolbox for future pathways that may include the
design of green ink formulations for solution-processed optoelectronic
devices
Introducing a New Potential Figure of Merit for Evaluating Microstructure Stability in Photovoltaic Polymer-Fullerene Blends
A theoretical
understanding of the microstructure of organic semiconducting
polymers and blends is vital to further advance the optoelectronic
device performance of organic electronics. We outline the theoretical
framework of a combined numerical approach based on polymeric solution
theory to study the microstructure of polymer:small molecule blends.
We feed the results of ab initio density functional theory quantum
chemistry calculations into an artificial neural network for the determination
of solubility parameters. These solubility parameters are used to
calculate Flory–Huggings intermolecular parameters. We further
show that the theoretical values are in line with experimentally determined
data. On the basis of the Flory–Huggings parameters, we establish
a figure of merit as a relative metric for assessing the phase diagrams
of organic semiconducting blends in thin films. This is demonstrated
for polymer:fullerene blend films on the basis of the prototypical
polymers poly(3-hexylthiophene-2,5-diyl) (P3HT) and poly[(5,6-difluoro-2,1,3-benzothiadiazol-4,7-diyl)-<i>alt</i>-(3,3-di(2-octyldodecyl)-2,2,5,2;5,2-quaterthiophen-5,5-diyl)]
(PffBT4T-2OD). After confirming the applicability of our model with
a broader range of materials and differences in molecular weight,
we suggest that this combined model should be able to inform design
criteria and processing guidelines for existing and new high performance
semiconducting blends for organic electronics applications with ideal
and stable solid state morphology