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Long Ye*, Sunsun Li, Xiaoyu Liu, Shaoqing Zhang, Masoud Ghasemi, Yuan Xiong, Jianhui Hou*, Harald Ade*. Joule, 2019, 3, 443-458 (DOI: https://doi.org/10.1016/j.joule.2018.11.006): Abstract Download The general lack of knowing the quench depth and the convolution with key kinetic factors has confounded deeper understanding of the respective importance of these factors in the morphology development of organic solar cells. Here, we determine the quench depth of a high-efficiency system and delineate the need to kinetically quench the mixed domains to a composition close to the percolation threshold. Importantly, the ability to achieve such a quench is very sensitive to structural parameters in polymer solar cells (PSCs) of the polymer PBDB-TF. Only the electricity kanji highest-molecular-weight polymer is able of earlier liquid-solid transition to “lock in” a high-performing PSC morphology with a composition above the miscibility limit and with an efficiency of over 13%. Systems with deep quench depths are therefore sensitive to molecular weight and the kinetic factors of the casting, likely impacting fabrication yield and reliability. They also need to be vitrified for stable performance.

Long Ye*, Yuan Xiong, Zheng Chen, Qianqian Zhang, Zhuping Fei, Reece Henry, Martin Heeney, Brendan T. O’Connor, Wei You*, Harald Ade*. Adv. Mater. 2019, DOI: 10.1002/adma.201808153: Abstract Download Casting of a donor:acceptor bulk‐heterojunction structure from a single ink has been the predominant fabrication method of organic photovoltaics (OPVs). Despite the success of such bulk heterojunctions, the task ofcontrolling the microstructure in a single casting process electricity grounding works has been arduous and alternative approaches are desired. To achieve OPVs with a desirable microstructure, a facile and eco‐compatible sequential deposition approach is demonstrated for polymer/small‐molecule pairs. Using a nominally amorphous polymer as the model material, the profound influence of casting solvent is shown on the molecular ordering of the film, and thus the device performance and mesoscale morphology of sequentially deposited OPVs can be tuned. Static and in situ X‐ray scattering indicate that applying (R)‐(+)‐limonene is able to greatly promote the molecular order of weakly crystalline polymers and form the largest domain spacing exclusively, which correlates well with the best efficiency of 12.5% in sequentially deposited devices. The sequentially cast device generally outperforms its control device based on traditional single‐ink bulk‐heterojunction structure. More crucially, a simple polymer:solvent interaction k electric share price forecast parameter χ is positively correlated with domain spacing in these sequentially deposited devices. These findings shed light on innovative approaches to rationally create environmentally friendly and highly efficient electronics.

Long Ye, Wanbin Li, Xia Guo*, Maojie Zhang*, Harald Ade*. Chem. Mater. 2019, DOI: 10.1021/acs.chemmater.9b00174: Abstract In addition to the innovation of nonfullerene acceptors, the development of highly efficient nonfullerene organic solar cells requires the design of new polymer donors and fundamental understanding of their structural and morphological properties. Utilizing meta-alkoxy-phenyl-substituted benzodithiophene and benzodithiophene-4,8-dione building blocks, we designed and prepared a class of structurally similar photovoltaic polymers named PBDx (x=1-4), which are capable of being processed from non-chlorinated solvents. From PBD1 to PBD4, the total carbon number of the alkyl side chains in each repeat unit increased by four in turn. The effect of side chain structure variation on the molecular aggregation, molecular arrangement, mesoscale phase separation, charge transport, and nonfullerene solar cell performance was systematically studied. Our hard and soft X-ray scattering results indicate that minor side chain variation yields vastly different molecular packing and mesoscale morphology for these analogues. It was found that PBD1 with the shortest alkyl side chain exhibited the strongest molecular aggregation, most attractive interaction with solvent additive, highest composition variation at a small length scale of 30 nm, and the best photovoltaic performance of over 12% efficiency electricity and magnetism review among the four polymers. Moreover, the structure-performance connections were discussed in the context of thermodynamics and the composition of the mixed domain was most likely quenched closer to the percolation threshold for the PBD1:IDIC system according to solubility limit measurements. This work thus elaborates the origin of such disparity in morphology and performance of nonfullerene solar cells.

Long Ye, Huawei Hu, Masoud Ghasemi, Tonghui Wang, Brian A Collins, Joo-Hyun Kim, Kui Jiang, Joshua H.Carpenter, Hong Li, Zhengke Li, Terry McAfee, Jingbo Zhao, Xiankai Chen, Joshua Yuk Lin Lai, Tingxuan Ma, Jean-Luc Bredas, He Yan*, Harald Ade*. Nature Materials, 2018, 17, 253–260: Abstract Download Although it is known that molecular interactions govern morphology formation and purity of mixed domains of conjugated polymer donors and small-molecule acceptors, and thus largely control the achievable performance of organic solar cells, quantifying interaction–function relations has remained elusive. Here, we first determine the temperature-dependent effective amorphous–amorphous interaction parameter, χaa(T), by mapping out the phase diagram of a model amorphous polymer:fullerene material system. We then establish a quantitative ‘constant-kink-saturation’ relation between χaa and the fill factor in organic solar cells that is verified in detail in a model system and delineated across numerous high- and low-performing materials systems, including fullerene and non-fullerene acceptors. Our experimental and computational data reveal that a high fill factor is obtained only when χaa is large enough to lead to strong phase separation. Our work outlines a basis for using various miscibility tests and future simulation methods that will significantly reduce or eliminate trial-and-error approaches to material synthesis and device fabrication of functional semiconducting blends and organic blends in general.

Long Ye, Brian Collins, Xuechen Jiao, Jingbo Zhao, He Yan, Harald Ade gas water heater reviews 2013*. Adv. Energy Mater. 2018, 8, 1703058 (Front Cover): Abstract Download Polymer solar cells (PSCs) continue to be a promising low-cost and lead-free photovoltaic technology. Of critical importance to PSCs is understanding and manipulating the composition of the amorphous mixed phase, which is governed 9gag tv by the thermodynamic molecular interactions of the polymer donor and acceptor molecules and the kinetics of the casting process. In this progress report, we will clarify and define nomenclature relating to miscibility and its relevance and implications to PSC devices in light of new developments. Utilizing a scanning transmission X-ray microscopy (STXM) method, the temperature dependences of “molecular miscibility” in the presence of PCBM crystals, now referred to liquidus miscibility, are presented for a number of representative blends. An emphasis is placed on relating the amorphous miscibility of high-efficiency PSC blends at a given processing temperature with their actual device performance and stability. It is shown and argued that a system with an amorphous miscibility close to percolation exhibits the most stable morphology. Furthermore, our progress report also outlines an approach to convert liquidus miscibility to an effective Flory-Huggins interaction parameter χ. Crucially, determination of temperature-dependent amorphous miscibility paves a way to rationally optimizing the stability and mixing behaviors of PSCs at actual processing and operating temperatures.