@article{dong_lee_song_neu_kashani_you_ade_2025, title={Control Over Vertical Composition in Low Complexity Polymer Solar Cells}, volume={1}, ISSN={["1614-6840"]}, url={https://doi.org/10.1002/aenm.202404962}, DOI={10.1002/aenm.202404962}, abstractNote={Abstract Inverted organic solar cells are promising due to their better stability compared to conventional structures. Donors with low synthetic complexity are desirable to lower costs. However, inverted devices are rarely used in low‐complexity systems. To investigate the reasons, the low‐complexity PTQ10:BTP‐eC9 binary system is benchmarked against the high‐complexity PM6:BTP‐eC9 system. In PTQ10:BTP‐eC9, where the efficiency of inverted devices lags the conventional structure significantly, distinct wetting layers are observed in conventional and inverted device structures. Conversely, the vertical distribution of PM6:BTP‐eC9 remains unaffected by changes in interlayer materials. The surface is always enriched in BTP‐eC9, but less for PM6. Importantly, the addition of PC 71 BM reduces the nonuniform vertical composition gradients. As the PC 71 BM concentration increases, the efficiency of the inverted PTQ10 devices approach that of the conventional devices and PTQ10:BTP‐eC9:PC 71 BM (1:1.2:0.4) exhibits negligible efficiency differences between inverted (14.01%) and conventional (14.49%) architectures. The concentration‐gradients aredriven by the interfacial energy between the active layer and interlayer materials and the casting kinetics in the case of the surface. Understanding the thermodynamic and kinetic aspects provides valuable insights for optimizing the performance of inverted organic solar cells, bringing them closer to practical applications.}, journal={ADVANCED ENERGY MATERIALS}, author={Dong, Xinyun and Lee, Byongkyu and Song, Runqiao and Neu, Justin and Kashani, Somayeh and You, Wei and Ade, Harald}, year={2025}, month={Jan} }
 @article{ren_song_zhu_o'connor_dong_2023, title={All Electrohydrodynamic Printed Flexible Organic Thin Film Transistors}, volume={6}, ISSN={["2365-709X"]}, url={https://doi.org/10.1002/admt.202300410}, DOI={10.1002/admt.202300410}, abstractNote={Abstract The demand of cost‐effective fabrication of printed flexible transistors has dramatically increased in recent years due to the need for flexible interface devices for various application including e‐skins, wearables, and medical patches. In this study, electrohydrodynamic (EHD) printing processes are developed to fabricate all the components of polymer‐based organic thin film transistors (OTFTs), including source/drain and gate electrodes, semiconductor channel, and gate dielectrics, which streamline the fabrication procedure for flexible OTFTs. The flexible transistors with top‐gate‐bottom‐contact configuration are fabricated by integrating organic semiconductor (i.e., poly(3‐hexylthiophene‐2,5‐diyl) blended with small molecule 2,7‐dioctyl[1]benzothieno[3,2‐b][1]benzothiophene), conductive polymer (i.e., poly (3,4‐ethylenedioxythiophene) polystyrene sulfonate), and ion‐gel dielectric. These functional inks are carefully designed with orthogonal solvents to enable their compatible printing into multilayered flexible OTFTs. The EHD printing process of each functional component is experimentally characterized and optimized. The fully EHD‐printed OTFTs show good electrical performance with mobility of 2.86 × 10 −1 cm 2 V −1 s −1 and on/off ratio of 10 4 , and great mechanical flexibility with small mobility change at bending radius of 6 mm and stable transistor response under hundreds of bending cycles. The demonstrated all printing‐based fabrication process provides a cost‐effective route toward flexible electronics with OTFTs.}, journal={ADVANCED MATERIALS TECHNOLOGIES}, author={Ren, Ping and Song, Runqiao and Zhu, Yong and O'Connor, Brendan and Dong, Jingyan}, year={2023}, month={Jun} }
 @article{ren_liu_song_o'connor_dong_zhu_2021, title={Achieving High-Resolution Electrohydrodynamic Printing of Nanowires on Elastomeric Substrates through Surface Modification}, volume={3}, ISSN={["2637-6113"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-85099220488&partnerID=MN8TOARS}, DOI={10.1021/acsaelm.0c00747}, abstractNote={Stretchable electronics based on nanomaterials has received much interest recently. However, it is challenging to print 1D nanomaterials (e.g., nanowires) with high resolution on stretchable elastomeric substrates. Electrohydrodynamic (EHD) printing has been used to print 1D nanomaterials such as silver nanowires (AgNWs) on stretchable substrates, but the resolution and electric conductivity of the printed patterns are typically low because of the poor wettability of the ink on the surface of the substrates. This paper reports a systematic study of two surface modification methods, UV–ozone treatment and dopamine coating, to modify the surface of polydimethylsiloxane (PDMS), which enables reliable and tunable EHD printing of AgNWs. The dynamic contact angle and the contact angle hysteresis were systematically studied to understand and evaluate the two surface modification methods. This work further investigates the hydrophobic stability of the two surface modification methods that is of critical relevance to the EHD printing, as it determines the shelf life of the treated samples. The effects of treatment dose and aging on the EHD printing performances, such as resolution and conductivity, were studied to find the feasible ranges of the parameters for the surface treatment and printing process. The surface modification methods along with the proper printing conditions can be selected to tailor and optimize the printing performance. A wearable electronic patch with a fractal pattern of AgNWs is printed on the modified PDMS substrate to demonstrate the potential of the reported surface modification for reliable EHD printing of AgNWs for stretchable devices.}, number={1}, journal={ACS APPLIED ELECTRONIC MATERIALS}, publisher={American Chemical Society (ACS)}, author={Ren, Ping and Liu, Yuxuan and Song, Runqiao and O'Connor, Brendan and Dong, Jingyan and Zhu, Yong}, year={2021}, month={Jan}, pages={192–202} }
 @article{balar_rech_siddika_song_schrickx_sheikh_ye_bonilla_awartani_ade_et al._2021, title={Resolving the Molecular Origin of Mechanical Relaxations in Donor-Acceptor Polymer Semiconductors}, volume={32}, ISSN={["1616-3028"]}, url={https://doi.org/10.1002/adfm.202105597}, DOI={10.1002/adfm.202105597}, abstractNote={Abstract The thermomechanical behavior of polymer semiconductors plays an important role in the processing, morphology, and stability of organic electronic devices. However, donor–acceptor‐based copolymers exhibit complex thermal relaxation behavior that is not well understood. This study uses dynamic mechanical analysis (DMA) to probe thermal relaxations of a systematic set of polymers based around the benzodithiophene (BDT) moiety. The loss tangent curves are resolved by fitting Gaussian functions to assign and distinguish different relaxations. Three prominent transitions are observed that correspond to: i) localized relaxations driven primarily by the side chains (γ ), ii) relaxations along the polymer backbone (β ), and iii) relaxations associated with aggregates (α ). The side chains are found to play a clear role in dictating T γ , and that mixing the side chain chemistry of the monomer to include alkyl and oligo(ethylene glycol) moieties results in splitting the γ ‐relaxation. The β relaxations are shown to be associated with backbone elements along with the monomer. In addition, through processing, it is shown that the α‐relaxation is due to aggregate formation. Finally, it is demonstrated that the thermal relaxation behavior correlates well with the stress–strain behavior of the polymers, including hysteresis and permanent set in cyclically stretched films.}, number={4}, journal={ADVANCED FUNCTIONAL MATERIALS}, publisher={Wiley}, author={Balar, Nrup and Rech, Jeromy James and Siddika, Salma and Song, Runqiao and Schrickx, Harry M. and Sheikh, Nadeem and Ye, Long and Bonilla, Anthony Megret and Awartani, Omar and Ade, Harald and et al.}, year={2021}, month={Oct} }
 @article{song_yao_liu_wang_dong_zhu_brendan t. o'connor_2020, title={Facile Approach to Fabricating Stretchable Organic Transistors with Laser-Patterned Ag Nanowire Electrodes}, volume={12}, ISSN={["1944-8252"]}, url={https://doi.org/10.1021/acsami.0c15339}, DOI={10.1021/acsami.0c15339}, abstractNote={Stretchable electronics are poised to revolutionize personal healthcare and robotics, where they enable distributed and conformal sensors. Transistors are fundamental building blocks of electronics, and there is a need to produce stretchable transistors using low-cost and scalable fabrication techniques. Here, we introduce a facile fabrication approach using laser patterning and transfer printing to achieve high-performance, solution-processed intrinsically stretchable organic thin-film transistors (OTFTs). The device consists of Ag nanowire (NW) electrodes, where the source and drain electrodes are patterned using laser ablation. The Ag NWs are then partially embedded in a poly(dimethylsiloxane) (PDMS) matrix. The electrodes are combined with a PDMS dielectric and polymer semiconductor, where the layers are individually transfer printed to complete the OTFT. Two polymer semiconductors, DPP-DTT and DPP-4T, are considered and show stable operation under the cyclic strain of 20 and 40%, respectively. The OTFTs maintain electrical performance by adopting a buckled structure after the first stretch-release cycle. The conformability and stretchability of the OTFT is also demonstrated by operating the transistor while adhered to a finger being flexed. The ability to pattern highly conductive Ag NW networks using laser ablation to pattern electrodes as well as interconnects provides a simple strategy to produce complex stretchable OTFT-based circuits.}, number={45}, journal={ACS APPLIED MATERIALS & INTERFACES}, publisher={American Chemical Society (ACS)}, author={Song, Runqiao and Yao, Shanshan and Liu, Yuxuan and Wang, Hongyu and Dong, Jingyan and Zhu, Yong and Brendan T. O'Connor}, year={2020}, month={Nov}, pages={50675–50683} }
 @article{sun_song_balar_sen_kline_brendan t. o'connor_2019, title={Impact of Substrate Characteristics on Stretchable Polymer Semiconductor Behavior}, volume={11}, ISSN={["1944-8252"]}, DOI={10.1021/acsami.8b16457}, abstractNote={Stretchable conductive polymer films are required to survive not only large tensile strain but also stay functional after the reduction in applied strain. In the deformation process, the elastomer substrate that is typically employed plays a critical role in response to the polymer film. In this study, we examine the role of a polydimethylsiloxane (PDMS) elastomer substrate on the ability to achieve stretchable PDPP-4T films. In particular, we consider the adhesion and near-surface modulus of the PDMS tuned through UV/ozone (UVO) treatment on the competition between film wrinkling and plastic deformation. We also consider the role of PDMS tension on the stability of films under cyclic strain. We find that increasing the near-surface modulus of the PDMS and maintaining the PDMS in tension throughout the cyclic strain process promote plastic deformation over film wrinkling. In addition, the UVO treatment increases film adhesion to the PDMS resulting in a significantly reduced film folding and delamination. For a 20 min UVO-treated PDMS, we show that a PDPP-4T film root-mean-square roughness is consistently below 3 nm for up to 100 strain cycles with a strain range of 40%. In addition, although the film is plastically deforming, the microstructural order is largely stable as probed by grazing incidence X-ray scattering and UV-visible spectroscopy. These results highlight the importance of neighboring elastomer characteristics on the ability to achieve stretchable polymer semiconductors.}, number={3}, journal={ACS APPLIED MATERIALS & INTERFACES}, author={Sun, Tianlei and Song, Runqiao and Balar, Nrup and Sen, Pratik and Kline, R. Joseph and Brendan T. O'Connor}, year={2019}, month={Jan}, pages={3280–3289} }
 @article{yao_ren_song_liu_huang_dong_o'connor_zhu_2019, title={Nanomaterial‐Enabled Flexible and Stretchable Sensing Systems: Processing, Integration, and Applications}, volume={32}, ISSN={0935-9648 1521-4095}, url={http://dx.doi.org/10.1002/adma.201902343}, DOI={10.1002/adma.201902343}, abstractNote={Abstract Nanomaterial‐enabled flexible and stretchable electronics have seen tremendous progress in recent years, evolving from single sensors to integrated sensing systems. Compared with nanomaterial‐enabled sensors with a single function, integration of multiple sensors is conducive to comprehensive monitoring of personal health and environment, intelligent human–machine interfaces, and realistic imitation of human skin in robotics and prosthetics. Integration of sensors with other functional components promotes real‐world applications of the sensing systems. Here, an overview of the design and integration strategies and manufacturing techniques for such sensing systems is given. Then, representative nanomaterial‐enabled flexible and stretchable sensing systems are presented. Following that, representative applications in personal health, fitness tracking, electronic skins, artificial nervous systems, and human–machine interactions are provided. To conclude, perspectives on the challenges and opportunities in this burgeoning field are considered.}, number={15}, journal={Advanced Materials}, publisher={Wiley}, author={Yao, Shanshan and Ren, Ping and Song, Runqiao and Liu, Yuxuan and Huang, Qijin and Dong, Jingyan and O'Connor, Brendan T. and Zhu, Yong}, year={2019}, month={Aug}, pages={1902343} }