@article{yang_fan_wang_yan_dong_cui_ade_li_2020, title={Impact of Isomer Design on Physicochemical Properties and Performance in High-Efficiency All-Polymer Solar Cells}, volume={53}, ISBN={1520-5835}, DOI={10.1021/acs.macromol.0c01405}, abstractNote={Combining the acceptor–donor–acceptor-type fused ring-based molecular architecture into a polymeric backbone is a promising strategy to design polymer acceptors for high-performance all-polymer sol...}, number={20}, journal={MACROMOLECULES}, author={Yang, Hang and Fan, Hongyu and Wang, Zhen and Yan, Hongping and Dong, Yingying and Cui, Chaohua and Ade, Harald and Li, Yongfang}, year={2020}, pages={9026–9033} }
 @article{gann_watson_tumbleston_cochran_yan_wang_seok_chabinyc_ade_2014, title={Topographic measurement of buried thin-film interfaces using a grazing resonant soft x-ray scattering technique}, volume={90}, ISSN={["1550-235X"]}, DOI={10.1103/physrevb.90.245421}, abstractNote={The internal structures of thin films, particularly interfaces between different materials, are critical to system properties and performance across many disciplines, but characterization of buried interface topography is often unfeasible. In this work, we demonstrate that grazing resonant soft x-ray scattering (GRSoXS), a technique measuring diffusely scattered soft x rays from grazing incidence, can reveal the statistical topography of buried thin-film interfaces. By controlling and predicting the x-ray electric field intensity throughout the depth of the film and simultaneously the scattering contrast between materials, we are able to unambiguously identify the microstructure at different interfaces of a model polymer bilayer system. We additionally demonstrate the use of GRSoXS to selectively measure the topography of the surface and buried polymer-polymer interface in an organic thin-film transistor, revealing different microstructure and markedly differing evolution upon annealing. In such systems, where only indirect control of interface topography is possible, accurate measurement of the structure of interfaces for feedback is critically important. While we demonstrate the method here using organic materials, we also show that the technique is readily extendable to any thin-film system with elemental or chemical contrasts exploitable at absorption edges.}, number={24}, journal={PHYSICAL REVIEW B}, author={Gann, Eliot and Watson, Anne and Tumbleston, John R. and Cochran, Justin and Yan, Hongping and Wang, Cheng and Seok, Jaewook and Chabinyc, Michael and Ade, Harald}, year={2014}, month={Dec} }
 @article{yan_wang_mccarn_ade_2013, title={Accurate and Facile Determination of the Index of Refraction of Organic Thin Films Near the Carbon 1s Absorption Edge}, volume={110}, ISSN={["1079-7114"]}, DOI={10.1103/physrevlett.110.177401}, abstractNote={A practical and accurate method to obtain the index of refraction, especially the decrement δ, across the carbon 1s absorption edge is demonstrated. The combination of absorption spectra scaled to the Henke atomic scattering factor database, the use of the doubly subtractive Kramers-Kronig relations, and high precision specular reflectivity measurements from thin films allow the notoriously difficult-to-measure δ to be determined with high accuracy. No independent knowledge of the film thickness or density is required. High confidence interpolation between relatively sparse measurements of δ across an absorption edge is achieved. Accurate optical constants determined by this method are expected to greatly improve the simulation and interpretation of resonant soft x-ray scattering and reflectivity data. The method is demonstrated using poly(methyl methacrylate) and should be extendable to all organic materials.}, number={17}, journal={PHYSICAL REVIEW LETTERS}, author={Yan, Hongping and Wang, Cheng and McCarn, Allison R. and Ade, Harald}, year={2013}, month={Apr} }
 @article{yan_collins_gann_wang_ade_mcneill_2012, title={Correlating the Efficiency and Nanomorphology of Polymer Blend Solar Cells Utilizing Resonant Soft X-ray Scattering}, volume={6}, ISSN={["1936-086X"]}, DOI={10.1021/nn204150f}, abstractNote={Enhanced scattering contrast afforded by resonant soft X-ray scattering (R-SoXS) is used to probe the nanomorphology of all-polymer solar cells based on blends of the donor polymer poly(3-hexylthiophene) (P3HT) with either the acceptor polymer poly((9,9-dioctylfluorene)-2,7-diyl-alt-[4,7-bis(3-hexylthien-5-yl)-2,1,3-benzothiadiazole]-2',2"-diyl) (F8TBT) or poly([N,N'-bis(2-octyldodecyl)-11-naphthalene-1,4,5,8-bis(dicarboximide)-2,6-diyl]-alt-5,5'-(2,2'-12-bithiophene)) (P(NDI2OD-T2)). Both P3HT:F8TBT and P3HT:P(NDI2OD-T2) blends processed from chloroform with subsequent annealing exhibit complicated morphologies with a hierarchy of phase separation. A bimodal distribution of domain sizes is observed for P3HT:P(NDI2OD-T2) blends with small domains of size ~5-10 nm that evolve with annealing and larger domains of size ~100 nm that are insensitive to annealing. P3HT:F8TBT blends in contrast show a broader distribution of domain size but with the majority of this blend structured on the 10 nm length scale. For both P3HT:P(NDI2OD-T2) and P3HT:F8TBT blends, an evolution in device performance is observed that is correlated with a coarsening and purification of domains on the 5-10 nm length scale. Grazing-incidence wide-angle X-ray scattering (GI-WAXS) is also employed to probe material crystallinity, revealing P(NDI2OD-T2) crystallites 25-40 nm in thickness that are embedded in the larger domains observed by R-SoXS. A higher degree of P3HT crystallinity is also observed in blends with P(NDI2OD-T2) compared to F8TBT with the propensity of the polymers to crystallize in P3HT:P(NDI2OD-T2) blends hindering the structuring of morphology on the sub-10 nm length scale. This work also underscores the complementarity of R-SoXS and GI-WAXS, with R-SoXS measuring the size of compositionally distinguishable domains and GI-WAXS providing information regarding crystallinity and crystallite thickness.}, number={1}, journal={ACS NANO}, author={Yan, Hongping and Collins, Brian A. and Gann, Eliot and Wang, Cheng and Ade, Harald and McNeill, Christopher R.}, year={2012}, month={Jan}, pages={677–688} }
 @article{yan_schuettfort_kronemeijer_mcneill_ade_2012, title={Influence of dielectric-dependent interfacial widths on device performance in top-gate P(NDI2OD-T2) field-effect transistors}, volume={101}, ISSN={["1077-3118"]}, DOI={10.1063/1.4748976}, abstractNote={Resonant soft x-ray reflectivity (R-SoXR) is employed to determine the interfacial widths of the semiconductor/dielectric interface in P(NDI2OD-T2)-based top-gate organic field-effect transistors (OFETs). It is shown that the deposition of a polymer dielectric on top of a semiconducting polymer layer can affect the interface structure, even when cast from an orthogonal solvent. The observed differences in the interfacial widths for different dielectrics explain the insensitivity of OFET performance to dielectric choice for OFETs fabricated using an identical fabrication protocol. The R-SoXR results demonstrate that differences in the physical interface structure should be taken into account when considering the influence of polymer dielectrics on the performance of all solution-processed OFETs. Specifically, the importance of the choice of solvent for the deposition is highlighted.}, number={9}, journal={APPLIED PHYSICS LETTERS}, author={Yan, Hongping and Schuettfort, Torben and Kronemeijer, Auke J. and McNeill, Christopher R. and Ade, Harald W.}, year={2012}, month={Aug} }
 @article{yan_schuettfort_kronemeijer_mcneill_ade_2012, title={Influence of dielectric-dependent interfacial widths on device performance in top-gate P(NDI2OD-T2) field-effect transistors (vol 101, 093308, 2012)}, volume={101}, number={17}, journal={Applied Physics Letters}, author={Yan, H. P. and Schuettfort, T. and Kronemeijer, A. J. and McNeill, C. R. and Ade, H. W.}, year={2012} }
 @article{collins_cochran_yan_gann_hub_fink_wang_schuettfort_mcneill_chabinyc_et al._2012, title={Polarized X-ray scattering reveals non-crystalline orientational ordering in organic films}, volume={11}, ISSN={1476-1122 1476-4660}, url={http://dx.doi.org/10.1038/nmat3310}, DOI={10.1038/nmat3310}, abstractNote={Molecular orientation critically influences the mechanical, chemical, optical and electronic properties of organic materials. So far, molecular-scale ordering in soft matter could be characterized with X-ray or electron microscopy techniques only if the sample exhibited sufficient crystallinity. Here, we show that the resonant scattering of polarized soft X-rays (P-SoXS) by molecular orbitals is not limited by crystallinity and that it can be used to probe molecular orientation down to size scales of 10 nm. We first apply the technique on highly crystalline small-molecule thin films and subsequently use its high sensitivity to probe the impact of liquid-crystalline ordering on charge mobility in polymeric transistors. P-SoXS also reveals scattering anisotropy in amorphous domains of all-polymer organic solar cells where interfacial interactions pattern orientational alignment in the matrix phase, which probably plays an important role in the photophysics. The energy and q-dependence of the scattering anisotropy allows the identification of the composition and the degree of orientational order in the domains.}, number={6}, journal={Nature Materials}, publisher={Springer Nature}, author={Collins, B. A. and Cochran, J. E. and Yan, H. and Gann, E. and Hub, C. and Fink, R. and Wang, C. and Schuettfort, T. and McNeill, C. R. and Chabinyc, M. L. and et al.}, year={2012}, month={Apr}, pages={536–543} }
 @article{gann_young_collins_yan_nasiatka_padmore_ade_hexemer_wang_2012, title={Soft x-ray scattering facility at the Advanced Light Source with real-time data processing and analysis}, volume={83}, ISSN={["1089-7623"]}, DOI={10.1063/1.3701831}, abstractNote={We present the development and characterization of a dedicated resonant soft x-ray scattering facility. Capable of operation over a wide energy range, the beamline and endstation are primarily used for scattering from soft matter systems around the carbon K-edge (∼285 eV). We describe the specialized design of the instrument and characteristics of the beamline. Operational characteristics of immediate interest to users such as polarization control, degree of higher harmonic spectral contamination, and detector noise are delineated. Of special interest is the development of a higher harmonic rejection system that improves the spectral purity of the x-ray beam. Special software and a user-friendly interface have been implemented to allow real-time data processing and preliminary data analysis simultaneous with data acquisition.}, number={4}, journal={REVIEW OF SCIENTIFIC INSTRUMENTS}, author={Gann, E. and Young, A. T. and Collins, B. A. and Yan, H. and Nasiatka, J. and Padmore, H. A. and Ade, H. and Hexemer, A. and Wang, C.}, year={2012}, month={Apr} }
 @article{yan_wang_garcia_swaraj_gu_mcneill_schuettfort_sohn_kramer_bazan_et al._2011, title={Interfaces in organic devices studied with resonant soft x-ray reflectivity}, volume={110}, ISSN={["1089-7550"]}, DOI={10.1063/1.3661991}, abstractNote={Interfaces between donor and acceptor semiconducting polymers are critical to the performance of polymer light-emitting diodes and organic solar cells. Similarly, interfaces between a conjugated polymer and a dielectric play a critical role in organic thin-film transistors. Often, these interfaces are difficult to characterize with conventional methods. Resonant soft x-ray reflectivity (R-SoXR) is a unique and relatively simple method to investigate such interfaces. R-SoXR capabilities are exemplified by presenting or discussing results from systems spanning all three device categories. We also demonstrate that the interfacial widths between active layers can be controlled by annealing at elevated temperature, pre-annealing of the bottom layer, or casting from different solvent mixtures. The extension of R-SoXR to the fluorine K absorption edge near 698 eV is also demonstrated.}, number={10}, journal={JOURNAL OF APPLIED PHYSICS}, author={Yan, Hongping and Wang, Cheng and Garcia, Andres and Swaraj, Sufal and Gu, Ziran and McNeill, Christopher R. and Schuettfort, Torben and Sohn, Karen E. and Kramer, Edward J. and Bazan, Guillermo C. and et al.}, year={2011}, month={Nov} }
 @article{yan_swaraj_wang_hwang_greenham_groves_ade_mcneill_2010, title={Influence of Annealing and Interfacial Roughness on the Performance of Bilayer Donor/Acceptor Polymer Photovoltaic Devices}, volume={20}, ISSN={["1616-3028"]}, DOI={10.1002/adfm.201001292}, abstractNote={Abstract}, number={24}, journal={ADVANCED FUNCTIONAL MATERIALS}, author={Yan, Hongping and Swaraj, Sufal and Wang, Cheng and Hwang, Inchan and Greenham, Neil C. and Groves, Chris and Ade, Harald and McNeill, Christopher R.}, year={2010}, month={Dec}, pages={4329–4337} }
 @article{swaraj_wang_yan_watts_lüning jan_mcneill_ade_2010, title={Nanomorphology of Bulk Heterojunction Photovoltaic Thin Films Probed with Resonant Soft X-ray Scattering}, volume={10}, ISSN={1530-6984 1530-6992}, url={http://dx.doi.org/10.1021/nl1009266}, DOI={10.1021/nl1009266}, abstractNote={The bulk nanomorphology of organic bulk heterojunction devices, particularly of all-polymer devices, is difficult to characterize due to limited electron density contrast between constituent materials. Resonant soft X-ray scattering can overcome this problem and is used to show that the morphologies in chloroform cast and subsequently annealed polyfluorene copolymer poly(9,9'-dioctylfluorene-co-bis(N,N'-(4,butylphenyl))bis(N,N'-phenyl-1,4-phenylene)diamine) (PFB) and poly(9,9'-dioctylfluorene-co-benzothiadiazole) (F8BT) blends exhibit a hierarchy of length scales with impure domains in as-cast films. With annealing, these domains first become purer at the smallest length scale and only then evolve in size with annealing. Even optimized cells using present fabrication methods are found to have a dominant domain size much larger than the exciton diffusion length. The observed morphology is far from ideal for efficient solar cell operation and very different from those achieved in high-efficiency fullerene-based devices. This strongly implies that lack of morphological control contributes to the relatively poor performance of the all-polymer PFB/F8BT devices and may be problematic for all-polymer devices in general. Novel processing strategies will have to be employed to harness the full potential these high open circuit voltage devices offer.}, number={8}, journal={Nano Letters}, publisher={American Chemical Society (ACS)}, author={Swaraj, Sufal and Wang, Cheng and Yan, Hongping and Watts, Benjamin and Lüning Jan and McNeill, Christopher R. and Ade, Harald}, year={2010}, month={Aug}, pages={2863–2869} }
 @article{swaraj_wang_araki_mitchell_liu_gaynor_deshmukh_yan_mcneill_ade_2009, title={The utility of resonant soft x-ray scattering and reflectivity for the nanoscale characterization of polymers}, volume={167}, ISSN={["1951-6355"]}, DOI={10.1140/epjst/e2009-00946-3}, journal={EUROPEAN PHYSICAL JOURNAL-SPECIAL TOPICS}, author={Swaraj, S. and Wang, C. and Araki, T. and Mitchell, G. and Liu, L. and Gaynor, S. and Deshmukh, B. and Yan, H. and McNeill, C. R. and Ade, H.}, year={2009}, month={Feb}, pages={121–126} }