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Abstract
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The poly(3-hexylthiophene) (P3HT)-based block copolymers were synthesized with hydrophilic and hydrophobic dielectric blocks including poly(ethylene glycol) (PEG), poly(methyl
methacrylate) (PMMA), and poly(styrene) (PS), and employed as morphology modifiers
(10–80 wt%) in P3HT: phenyl-C71-butyric acid methyl ester (PC71BM) bulk heterojunction
(BHJ) solar cells. The advantages and drawbacks of the coily blocks were also outlined from
perspective of photovoltaic characteristics. A novel matrix-bridged disperses model was
proposed to map out well-connected BHJ networks, which was consistent with the scattering data. Rod-coil block copolymers simultaneously controlled some main properties,
i.e., crystallinity, d-spacing, domain sizes, and stability. Hydrophobic-based block copolymers (P3HT-b-PS and P3HT-b-PMMA) increased crystallinity, P3HT crystallite size, and
PC71BM cluster size and decreasedd-spacings. This reflected larger and denser P3HT crystallites and coarser and more packed PC71BM clusters. P3HT crystallites grew up to60
and 30 nm in (1 0 0) and (0 2 0) directions, respectively. In 30 wt% of P3HT7150-b-PS,
PC71BM clusters were also the largest (=38.87 nm). A fully interdigitated hexyl chains
(10.05 Å) was acquired in 80 wt% of P3HT7150-b-PS. Impressing trends of the P3HT-bPMMA copolymers resembled that of P3HT-b-PS ones, but with a smoother slope. In contrast, hydrophilic-based block copolymers (P3HT-b-PEG and P3HT-b-PEG-b-P3HT) resulted
in finer and looser P3HT crystallites and PC71BM clusters. The largest d-spacings in the
directions of the hexyl side chains (=19.97 Å) andp-pstacking (=4.95 Å) were detected
in 80 wt% of P3HT7150-b-PEG750. The lowest (=3.51 Å) and highest (=5.63 Å) d-spacings
for PC71BM clusters appeared in 80 wt% of P3HT7150-b-PS and P3HT7150-b-PEG750, respectively. Unlike PEG-based block copolymers, in P3HT-b-PS and P3HT-b-PMMA ones, lower
P3HT molecular weights conduced to higher power conversion efficiencies (PCE= 4.43%).
The short curr
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