33 research outputs found
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
Rapid flash annealing of thermally reactive copolymers in a roll-to-roll process for polymer solar cells
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
Comparative studies of photochemical cross-linking methods for stabilizing the bulk hetero-junction morphology in polymer solar cells
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
propertiesanother important codeterminant is the packing structuresome
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