Developing Y‐Branched Polymer Acceptor with 3D Architecture to Reconcile Between Crystallinity and Miscibility Yielding >15% Efficient All‐Polymer Solar Cells

Abstract

In all-polymer solar cells (all-PSCs), there remains such a dilemma that obtains good miscibility and crystallinity simultaneously. Herein a new family of Y-shape polymer acceptor, namely PYTT is developed, which is copolymerized from Y6 and benzotrithiophene units in three-way directions. Benefiting from its high-density end-chains and extended 𝝅-conjugation thanks to highly-branched 3D architecture, PYTT displays better organic solubility despite much higher molecular weights, larger crystallinity, and tighter 𝝅-stacking than the linear counterpart-PYT comprising Y6 and thiophene moieties, while showing identical optical absorption yet threefold higher photoluminescence intensity. In PYTT blend film with PM6 polymer donor, the interpenetrating nano-fibrillar structures are formed with well-intermixed polymeric domain sizes close to the exciton diffusion length, which is greatly conducive to exciton dissociation and charge transport in device. Consequently, PYTT-based all-PSCs exhibit all increased photovoltaic parameters, yielding a decent power conversion efficiency of 15.60%, which is ≈20% enhancement over PYT-based device, along with low nonradiative loss of 0.221 meV.

Y-Series-Based Polymer Acceptors for High-Performance All-Polymer Solar Cells in Binary and Non-binary Systems

“…Simple aromatic all-fused rings or unfused backbones with non-covalent interactions, such as S···N, F···H, or O···H, − can be incorporated into the design of new polymer acceptors to reduce production costs and enhance device stability. Highly branched polymer structures have been developed to realize 3D networks with good crystallinity and solubility . Besides, by connecting two SMAs through a π-bridge, the design of A-π-A (N-π-N) quasi-macromolecule acceptors , increases the conjugation length for more electron delocalization while still maintaining definite molecular structures with fewer chain entanglements.…”

Recent Developments of Polymer Solar Cells with Photovoltaic Performance over 17%

“…Hence, the device efficiency based on polymeric small molecule acceptors is gradually close to that of small molecular acceptors, but there are still certain gaps to be overcome. [ 103–106 ]…”

“…Hence, the device efficiency based on polymeric small molecule acceptors is gradually close to that of small molecular acceptors, but there are still certain gaps to be overcome. [103][104][105][106] However, the improvement of ADA'DA-type acceptors from fused rings, end groups and side chains cannot satisfy the development of this kind of materials, and the recently emerging high-performance polymer acceptors achieved by the regulation of linking units have shown potential advantages in arrange macromolecular chains more compact and order. [105,107,108] Wei et al [109] synthesized a novel oligomer acceptor 2BTP-2F-T by linking two ADA'DA-type NFA via thiophene unit.…”

Central Core Substitutions and Film‐Formation Process Optimization Enable Approaching 19% Efficiency All‐Polymer Solar Cells

“…As a result, the structural modification of SMA monomer normally involves inner and outer alkyl chains, end group, halogen atom substitution, etc. [35][36][37] It is interesting to note that regulating conjugated central core is rare in PSMAs, although this strategy has shown excellent effect in SMA-based OSCs recently. [38,39] For instance, our group reported Qx-series acceptors using quinoxaline (Qx) fused as the central core in SMAs, which showed dramatic effects on molecular stacking behavior, film transport properties, and energy loss.…”