The kinetic and thermodynamic characteristics of polymerizations following a cooperative, nucleation-elongation mechanism are discussed in comparison to those of non-cooperative, isodesmic polymerizations. Nucleation-elongation polymerization is a relatively unexplored avenue of synthetic polymer chemistry and offers some unique and interesting thermodynamic and kinetic attributes not found in the more classical mechanisms of polymer chemistry.

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Morphology control of solution coated solar cell materials presents a key challenge limiting their device performance and commercial viability. Here we present a new concept for controlling phase separation during solution printing using an all-polymer bulk heterojunction solar cell as a model system. The key aspect of our method lies in the design of fluid flow using a microstructured printing blade, on the basis of the hypothesis of flow-induced polymer crystallization. Our flow design resulted in a ∼90% increase in the donor thin film crystallinity and reduced microphase separated donor and acceptor domain sizes. The improved morphology enhanced all metrics of solar cell device performance across various printing conditions, specifically leading to higher short-circuit current, fill factor, open circuit voltage and significantly reduced device-to-device variation. We expect our design concept to have broad applications beyond all-polymer solar cells because of its simplicity and versatility.

A new polymer acceptor, naphthodiperylenetetraimide-vinylene (NDP-V), featuring a backbone of altenating naphthodiperylenetetraimide and vinylene units is designed and applied in all-polymer solar cells (all-PSCs). With this polymer acceptor, a new record power-conversion efficiencies (PCE) of 8.59% has been achieved for all-PSCs. The design principle of NDP-V is to reduce the conformational disorder in the backbone of a previously developed high-performance acceptor, PDI-V, a perylenediimide-vinylene polymer. The chemical modifications result in favorable changes to the molecular packing behaviors of the acceptor and improved morphology of the donor-acceptor (PTB7-Th:NDP-V) blend, which is evidenced by the enhanced hole and electron transport abilities of the active layer. Moreover, the stronger absorption of NDP-V in the shorter-wavelength range offers a better complement to the donor. All these factors contribute to a short-circuit current density (J ) of 17.07 mA cm . With a fill factor (FF) of 0.67, an average PCE of 8.48% is obtained, representing the highest value thus far reported for all-PSCs.