Publications

@article{Yang2020,
title = {In Situ Studies of Solvent Additive Effects on the Morphology Development during Printing of Bulk Heterojunction Films for Organic Solar Cells},
author = {Dan Yang and Sebastian Grott and Xinyu Jiang and Kerstin S Wienhold and Matthias Schwartzkopf and Stephan V Roth and Peter Müller-Buschbaum},
url = {https://onlinelibrary.wiley.com/doi/abs/10.1002/smtd.202000418},
doi = {https://doi.org/10.1002/smtd.202000418},
year = {2020},
date = {2020-01-01},
journal = {Small Methods},
volume = {4},
number = {9},
pages = {2000418},
abstract = {Abstract The development of polymer morphology and crystallinity of printed bulk heterojunction (BHJ) films doped with the different solvent additives 1,8-diiodooctane (DIO) or diphenyl ether (DPE) is investigated with in situ grazing-incidence small/wide-angle X-ray scattering. The solvent additives, having different boiling points, lead to a different film drying behavior and morphology growth states in the BHJ films of the benzothiadiazole-based polymer (PPDT2FBT) and [6,6]-phenyl-C71-butyric acid methyl ester (PC71BM). The phase demixing in the printed films is changing over time along with solvent evaporation. Polymer domains start aggregating to form larger domains in the liquid–liquid phase, while phase separation mainly occurs in the liquid–solid phase. The present work provides a profound insight into the morphology development of printed BHJ films doped with different solvent additives, which is particularly important for the large-scale fabrication of organic photovoltaics.},
keywords = {crystallinity, morphology, PPDT2FBT:PC71BM films, printing, solvent additive},
pubstate = {published},
tppubtype = {article}
}

@article{Yang2020a,
title = {In Operando GISAXS and GIWAXS Stability Study of Organic Solar Cells Based on PffBT4T-2OD:PC71BM with and without Solvent Additive},
author = {Dan Yang and Franziska C Löhrer and Volker Körstgens and Armin Schreiber and Bing Cao and Sigrid Bernstorff and Peter Müller-Buschbaum},
url = {https://onlinelibrary.wiley.com/doi/abs/10.1002/advs.202001117},
doi = {https://doi.org/10.1002/advs.202001117},
year = {2020},
date = {2020-01-01},
journal = {Advanced Science},
volume = {7},
number = {16},
pages = {2001117},
abstract = {Abstract Solvent additives are known to modify the morphology of bulk heterojunction active layers to achieve high efficiency organic solar cells. However, the knowledge about the influence of solvent additives on the morphology degradation is limited. Hence, in operando grazing-incidence small and wide angle X-ray scattering (GISAXS and GIWAXS) measurements are applied on a series of PffBT4T-2OD:PC71BM-based solar cells prepared without and with solvent additives. The solar cells fabricated without a solvent additive, with 1,8-diiodoctane (DIO), and with o-chlorobenzaldehyde (CBA) additive show differences in the device degradation and changes in the morphology and crystallinity of the active layers. The mesoscale morphology changes are correlated with the decay of the short-circuit current Jsc and the evolution of crystalline grain sizes is codependent with the decay of open-circuit voltage Voc. Without additive, the loss in Jsc dominates the degradation, whereas with solvent additive (DIO and CBA) the loss in Voc rules the degradation. CBA addition increases the overall device stability as compared to DIO or absence of additive.},
keywords = {crystallinity, degradation, in operando, organic photovoltaics, solvent additives},
pubstate = {published},
tppubtype = {article}
}