6 research outputs found
Computer-Aided Screening of Conjugated Polymers for Organic Solar Cell: Classification by Random Forest
Owing to the diverse
chemical structures, organic photovoltaic
(OPV) applications with a bulk heterojunction framework have greatly
evolved over the last two decades, which has produced numerous organic
semiconductors exhibiting improved power conversion efficiencies (PCEs).
Despite the recent fast progress in materials informatics and data
science, data-driven molecular design of OPV materials remains challenging.
We report a screening of conjugated molecules for polymer–fullerene
OPV applications by supervised learning methods (artificial neural
network (ANN) and random forest (RF)). Approximately 1000 experimental
parameters including PCE, molecular weight, and electronic properties
are manually collected from the literature and subjected to machine
learning with digitized chemical structures. Contrary to the low correlation
coefficient in ANN, RF yields an acceptable accuracy, which is twice
that of random classification. We demonstrate the application of RF
screening for the design, synthesis, and characterization of a conjugated
polymer, which facilitates a rapid development of optoelectronic materials
Exploring Alkyl Chains in Benzobisthiazole-Naphthobisthiadiazole Polymers: Impact on Solar-Cell Performance, Crystalline Structures, and Optoelectronics
The
shapes and lengths of the alkyl chains of conjugated polymers
greatly affect the efficiencies of organic photovoltaic devices. This
often results in a trade-off between solubility and self-organizing
behavior; however, each material has specific optimal chains. Here
we report on the effect of alkyl side chains on the film morphologies,
crystallinities, and optoelectronic properties of new benzobisthiazole-naphthobisthiadiazole
(PBBT-NTz) polymers. The power conversion efficiencies (PCEs) of linear-branched
and all-branched polymers range from 2.5% to 6.6%; the variations
in these PCEs are investigated by atomic force microscopy, two-dimensional
X-ray diffraction (2D-GIXRD), and transient photoconductivity techniques.
The best-performing linear-branched polymer, bearing dodecyl and decyltetradecyl
chains (C12-DT), exhibits nanometer-scale fibers along with the highest
crystallinity, comprising predominant edge-on and partial face-on
orientations. This morphology leads to the highest photoconductivity
and the longest carrier lifetime. These results highlight the importance
of long alkyl chains for inducing intermolecular stacking, which is
in contrast to observations made for analogous previously reported
polymers