@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{min_chen_chen_sun_lee_li_zhu_brendan t. o'connor_parsons_chang_2018, title={Conformal Physical Vapor Deposition Assisted by Atomic Layer Deposition and Its Application for Stretchable Conductors}, volume={5}, ISSN={["2196-7350"]}, DOI={10.1002/admi.201801379}, abstractNote={Abstract}, number={22}, journal={ADVANCED MATERIALS INTERFACES}, author={Min, Joong-Hee and Chen, Yi-An and Chen, I-Te and Sun, Tianlei and Lee, Dennis T. and Li, Chengjun and Zhu, Yong and Brendan T. O'Connor and Parsons, Gregory N. and Chang, Chih-Hao}, year={2018}, month={Nov} }
 @article{yu_chung_shewmon_ho_carpenter_larrabee_sun_jones_ade_o'connor_et al._2017, title={Flexible inorganic ferroelectric thin films for nonvolatile memory devices}, volume={27}, number={21}, journal={Advanced Functional Materials}, author={Yu, H. and Chung, C. C. and Shewmon, N. and Ho, S. and Carpenter, J. H. and Larrabee, R. and Sun, T. L. and Jones, J. L. and Ade, H. and O'Connor, B. T. and et al.}, year={2017} }
 @article{sun_scott_wang_kline_bazan_brendan t. o'connor_2017, title={Plastic Deformation of Polymer Blends as a Means to Achieve Stretchable Organic Transistors}, volume={3}, ISSN={["2199-160X"]}, DOI={10.1002/aelm.201600388}, abstractNote={Intrinsically stretchable semiconductors will facilitate the realization of seamlessly integrated stretchable electronics. In this study, a new approach to achieve intrinsically stretchable semiconductors is introduced by blending a rigid high‐performance donor–acceptor polymer semiconductor poly[4‐(4,4‐dihexadecyl‐4H‐cyclopenta[1,2‐b:5,4‐b′]dithiopen‐2‐yl)‐alt[1,2,5]thiadiazolo[3,4‐c]pyridine] with a ductile polymer semiconductor poly(3‐hexylthiophene). Under large tensile strains of up to 75%, the polymers are shown to orient in the direction of strain, and when the strain is reduced, the polymers reversibly deform. During cyclic strain, the local packing order of the polymers is shown to be remarkably stable. The saturated field effect charge mobility is shown to be consistently above 0.04 cm2 V−1 s−1 for up to 100 strain cycles with strain ranging from 10% to 75% when the film is printed onto a rigid test bed. At the 75% strain state, the charge mobility is consistently above 0.15 cm2 V−1 s−1. Ultimately, the polymer blend process introduced here results in an excellent combination of device performance and stretchability providing an effective approach to achieve intrinsically stretchable semiconductors.}, number={1}, journal={ADVANCED ELECTRONIC MATERIALS}, author={Sun, Tianlei and Scott, Joshua I. and Wang, Ming and Kline, Regis Joseph and Bazan, Guillermo C. and Brendan T. O'Connor}, year={2017}, month={Jan} }
 @article{o'connor_xue_sun_2015, title={Charge transport in highly aligned conjugated polymers}, volume={9568}, ISSN={["0277-786X"]}, DOI={10.1117/12.2187646}, abstractNote={Charge transport in conjugated polymers has a complex dependence on film morphology. Aligning the polymer chains in the plane of the film simplifies the morphology of the system allowing for insight into the morphological dependence of charge transport. Highly aligned conjugated polymers have also been shown to lead to among the highest reported field effect mobilities in these materials to date. In this talk, a comparison will be made between aligned polymer films processed using two primary methods, nanostructured substrate assisted growth and mechanical strain. A number of polymer systems including P3HT, pBTTT, N2200, and PCDTPT are considered, and the processed films are analyzed in detail with optical spectroscopy, AFM, TEM, and X-ray scattering providing insight into the molecular features that allow for effective alignment. By contrasting the morphology of these films, several insights into underlying charge transport limitations can be made. A number of key morphological features that lead to high field effect mobility and charge transport anisotropy in these films will be discussed. In addition, several unique features of organic thin film transistor device behavior in these systems will be examined including the commonly observed gate voltage dependence of saturated field effect mobility.}, journal={ORGANIC FIELD-EFFECT TRANSISTORS XIV; AND ORGANIC SENSORS AND BIOELECTRONICS VIII}, author={O'Connor, Brendan and Xue, Xiao and Sun, Tianlei}, year={2015} }
 @article{sun_peavey_shelby_ferguson_brendan t. o'connor_2015, title={Heat shrink formation of a corrugated thin film thermoelectric generator}, volume={103}, ISSN={["1879-2227"]}, DOI={10.1016/j.enconman.2015.07.016}, abstractNote={A thin film thermoelectric (TE) generator with a corrugated architecture is demonstrated formed using a heat-shrink fabrication approach. Fabrication of the corrugated TE structure consists of depositing thin film thermoelectric elements onto a planar non-shrink polyimide substrate that is then sandwiched between two uniaxial stretch-oriented co-polyester (PET) films. The heat shrink PET films are adhered to the polyimide in select locations, such that when the structure is placed in a high temperature environment, the outer films shrink resulting in a corrugated core film and thermoelectric elements spanning between the outer PET films. The module has a cross-plane heat transfer architecture similar to a conventional bulk TE module, but with heat transfer in the plane of the thin film thermoelectric elements, which assists in maintaining a significant temperature difference across the thermoelectric junctions. In this demonstration, Ag and Ni films are used as the thermoelectric elements and a Seebeck coefficient of 14 μV K−1 is measured with a maximum power output of 0.22 nW per couple at a temperature difference of 7.0 K. We then theoretically consider the performance of this device architecture with high performance thermoelectric materials in the heat sink limited regime. The results show that the heat-shrink approach is a simple fabrication method that may be advantageous in large-area, low power density applications. The fabrication method is also compatible with simple geometric modification to achieve various form factors and power densities to customize the TE generator for a range of applications.}, journal={ENERGY CONVERSION AND MANAGEMENT}, author={Sun, Tianlei and Peavey, Jennifer L. and Shelby, M. David and Ferguson, Scott and Brendan T. O'Connor}, year={2015}, month={Oct}, pages={674–680} }