8 research outputs found
Controlling Internal Pore Sizes in Bicontinuous Polymeric Nanospheres
Complex polymeric nanospheres were formed in water from comb-like amphiphilic block copolymers. Their internal morphology was determined by three-dimensional cryo-electron tomographic analysis. Varying the polymer molecular weight (MW) and the hydrophilic block weight content allowed for fine control over the internal structure. Construction of a partial phase diagram allowed us to determine the criteria for the formation of bicontinuous polymer nanosphere (BPN), namely for copolymers with MW of up to 17?kDa and hydrophilic weight fractions of ?0.25; and varying the organic solvent to water ratio used in their preparation allowed for control over nanosphere diameters from 70 to 460?nm. Significantly, altering the block copolymer hydrophilic–hydrophobic balance enabled control of the internal pore diameter of the BPNs from 10 to 19?nm
Triplet Exciton Generation in Bulk-Heterojunction Solar Cells based on Endohedral Fullerenes
Organic bulk-heterojunctions (BHJ) and solar cells containing the trimetallic
nitride endohedral fullerene 1-[3-(2-ethyl)hexoxy
carbonyl]propyl-1-phenyl-Lu3N@C80 (Lu3N@C80-PCBEH) show an open circuit voltage
(VOC) 0.3 V higher than similar devices with [6,6]-phenyl-C[61]-butyric acid
methyl ester (PC61BM). To fully exploit the potential of this acceptor molecule
with respect to the power conversion efficiency (PCE) of solar cells, the short
circuit current (JSC) should be improved to become competitive with the state
of the art solar cells. Here, we address factors influencing the JSC in blends
containing the high voltage absorber Lu3N@C80-PCBEH in view of both
photogeneration but also transport and extraction of charge carriers. We apply
optical, charge carrier extraction, morphology, and spin-sensitive techniques.
In blends containing Lu3N@C80-PCBEH, we found 2 times weaker photoluminescence
quenching, remainders of interchain excitons, and, most remarkably, triplet
excitons formed on the polymer chain, which were absent in the reference
P3HT:PC61BM blends. We show that electron back transfer to the triplet state
along with the lower exciton dissociation yield due to intramolecular charge
transfer in Lu3N@C80-PCBEH are responsible for the reduced photocurrent
Three-Dimensional Structure of P3HT Assemblies in Organic Solvents Revealed by Cryo-TEM
Poly(3-hexylthiophene)
(P3HT) assemblies in vitrified organic solvents
were visualized at nanometer scale resolution by cryo-transmission
electron microscopy, low dose electron diffraction, and cryo-tomography
revealing a three-dimensional lamellar structure formed by the stacking
of the conjugated backbones of P3HT with a distance of 1.7 nm and
increased order in the bulk of the nanowire. This combination of techniques
reveals local structures in dispersion and the condensed state that
play a crucial role in the performance of organic electronic devices
Bicontinuous Nanospheres from Simple Amorphous Amphiphilic Diblock Copolymers
Bicontinuous
nanospheres have been observed (although rarely) from
a variety of block copolymers with architectural and compositional
complexity, and often in the presence of additives. Unlocking key
features involved in their formation presents possibilities for bicontinuous
aggregates with varied functionality and application. An attractive
prospect is the ability to form them from much simpler polymeric structures
derived from facile syntheses. To that end, we herein report the formation
of bicontinuous aggregates from simple amorphous amphiphilic diblock
copolymers of poly(ethylene oxide)-<i>b</i>-poly(<i>n</i>-butyl methacrylate), analogous to our previous report
of the same from a semicrystalline comb-like block copolymer. Moreover,
we demonstrate that polymorphism can be achieved by altering the relative
block proportions and the nonselective cosolvent. We find that the
polymeric structure is not the dominating factor in the formation
of bicontinuous nanospheres but that the choice of cosolvent for the
hydrophilic block appears to have greater influence on determining
the end morphology
Bicontinuous Nanospheres from Simple Amorphous Amphiphilic Diblock Copolymers
Bicontinuous
nanospheres have been observed (although rarely) from
a variety of block copolymers with architectural and compositional
complexity, and often in the presence of additives. Unlocking key
features involved in their formation presents possibilities for bicontinuous
aggregates with varied functionality and application. An attractive
prospect is the ability to form them from much simpler polymeric structures
derived from facile syntheses. To that end, we herein report the formation
of bicontinuous aggregates from simple amorphous amphiphilic diblock
copolymers of poly(ethylene oxide)-<i>b</i>-poly(<i>n</i>-butyl methacrylate), analogous to our previous report
of the same from a semicrystalline comb-like block copolymer. Moreover,
we demonstrate that polymorphism can be achieved by altering the relative
block proportions and the nonselective cosolvent. We find that the
polymeric structure is not the dominating factor in the formation
of bicontinuous nanospheres but that the choice of cosolvent for the
hydrophilic block appears to have greater influence on determining
the end morphology
Bicontinuous Nanospheres from Simple Amorphous Amphiphilic Diblock Copolymers
Bicontinuous nanospheres have been observed (although rarely) from a variety of block copolymers with architectural and compositional complexity, and often in the presence of additives. Unlocking key features involved in their formation presents possibilities for bicontinuous aggregates with varied functionality and application. An attractive prospect is the ability to form them from much simpler polymeric structures derived from facile syntheses. To that end, we herein report the formation of bicontinuous aggregates from simple amorphous amphiphilic diblock copolymers of poly(ethylene oxide)-b-poly(n-butyl methacrylate), analogous to our previous report of the same from a semicrystalline comb-like block copolymer. Moreover, we demonstrate that polymorphism can be achieved by altering the relative block proportions and the nonselective cosolvent. We find that the polymeric structure is not the dominating factor in the formation of bicontinuous nanospheres but that the choice of cosolvent for the hydrophilic block appears to have greater influence on determining the end morpholog