Electrical characterization of fluorinated benzothiadiazole based conjugated copolymer – a promising material for high-performance solar cells

Measurements of electrical conductivity, electron work function, carrier mobility of holes and the diffusion length of excitons were performed on samples of conjugated polymers relevant to polymer solar cells. A state of the art fluorinated benzothiadiazole based conjugated copolymer (PBDTTHD − DTBTff) was studied and benchmarked against the reference polymer poly-3-hexylthiophene (P3HT). We employed, respectively, four electrode conductivity measurements, Kelvin probe work function measurements, carrier mobility using charge extraction by linearly increasing voltage (CELIV) measurements and diffusion length determinaton using surface photovoltage measurements

Controlling anomalous stresses in soft field-responsive systems

We report a new phenomenon occurring in field-responsive suspensions: shear-induced anomalous stresses. Competition between a rotating field and a shear flow originates a multiplicity of anomalous stress behaviors in suspensions of bounded dimers constituted by induced dipoles. The great variety of stress regimes includes non-monotonous behaviors, multi-resonances, negative viscosity effect and blockades. The reversibility of the transitions between the different regimes and the self-similarity of the stresses make this phenomenon controllable and therefore applicable to modify macroscopic properties of soft condensed matter phasesComment: 5 pages, 6 figures, submitted to PR

In-line, roll-to-roll morphology analysis of organic solar cell active layers

Polymer conformation in solution is more important for R2R solar cell performance than the crystallinity of the final coated film.</p

Women and leadership in higher education in China: discourse and the discursive construction of identity

Prior research indicates that just 4.5 percent of mainland China’s higher educational institution leaders are female. This article extends theory and research by drawing attention to identity and Discourse as an important, yet under-researched, aspect of the problem of women’s underrepresentation in higher education leadership. Drawing on in-depth qualitative interviews with nine female academics in Chinese universities and informed by discursive approaches to identity and constructionist views, we analyze how women construct multiple identities, the interplay of identities, and the influence of broader societal Discourses of gender and leadership. The findings highlight the interplay between competing multiple identities, and illustrate how the women’s identities are shaped and constrained by dominant historical and cultural Discourses in Chinese society, which results in identity regulation (Alvesson and Billing 2009), notably identity positioning that is congruent with social norms and conventions. A key finding is that the female academics reject the leader identity. This is true for those in middle management positions, as well as women in early career stages, who might otherwise aspire to leadership. Implications for the leadership pipeline in China’s universities is discussed and recommendations are made for future research directions

Gender‐Informed Mentoring Strategies for Women Engineering Scholars: On Establishing a Caring Community

Improved mentoring of women graduate students and young faculty is one strategy for increasing the presence, retention and advancement of women scholars in engineering. We explore the sociological literature on interpersonally‐ and institutionally‐generated gender roles and dynamics that make the construction and maintenance of mentoring relationships especially difficult for women in male‐dominated fields. In addition, we review non‐traditional strategies including peer‐, multiple‐ and collective mentorships that are likely to be more successful for most women (and many men). Finally, organizational change strategies designed to provide a more egalitarian and cooperative atmosphere in engineering programs and departments are presented. These ideas represent a social contract for a caring community more supportive of all members' personal and professional growth and success.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/95139/1/j.2168-9830.2002.tb00672.x.pd

Mechanical Properties of a Library of Low-Band-Gap Polymers

The mechanical properties of low-band-gap polymers are important for the long-term survivability of roll-to-roll processed organic electronic devices. Such devices, e.g., solar cells, displays, and thin-film transistors, must survive the rigors of roll-to-roll coating and also thermal and mechanical forces in the outdoor environment and in stretchable and ultraflexible form factors. This paper measures the stiffness (tensile modulus), ductility (crack-onset strain), or both of a combinatorial library of 51 low-band-gap polymers. The purpose of this study is to systematically screen a library of low-band-gap polymers to better understand the connection between molecular structures and mechanical properties in order to design conjugated polymers that permit mechanical robustness and even extreme deformability. While one of the principal conclusions of these experiments is that the structure of an isolated molecule only partially determines the mechanical propertiesanother important codeterminant is the packing structuresome general trends can be identified. (1) Fused rings tend to increase the modulus and decrease the ductility. (2) Branched side chains have the opposite effect. Despite the rigidity of the molecular structure, the most deformable films can be surprisingly compliant (modulus ≥ 150 MPa) and ductile (crack-onset strain ≤ 68%). This paper concludes by proposing a new composite merit factor that combines the power conversion efficiency in a fully solution processed device obtained via roll and roll-to-roll coating and printing (as measured in an earlier paper) and the mechanical deformability toward the goal of producing modules that are both efficient and mechanically stable