Schofield Ryan M, Maciejewska Barbara M, Elmestekawy Karim A, Woolley Jack M, Tebbutt George T, Danaie Mohsen, Allen Christopher S, Herz Laura M, Assender Hazel E, Grobert Nicole
Department of Materials, University of Oxford, Parks Road, Oxford, OX1 3PH, UK.
Department of Physics, University of Oxford, Clarendon Laboratory, Parks Road, Oxford, OX1 3PU, UK.
Small. 2025 Jan;21(3):e2409269. doi: 10.1002/smll.202409269. Epub 2024 Nov 22.
Nanofibrous active layers offer hierarchical control over molecular structure, and the size and distribution of electron donor:acceptor domains, beyond conventional organic photovoltaic architectures. This structure is created by forming donor pathways via electrospinning nanofibers of semiconducting polymer, then infiltrating with an electron acceptor. Electrospinning induces chain and crystallite alignment, resulting in enhanced light-harvesting and charge transport. Here, the charge transport capabilities are predicted, and charge separation and dynamics are evaluated in these active layers, to assess their photovoltaic potential. Through X-ray and electron diffraction, the fiber nanostructure is elucidated, with uniaxial elongation of the electrospinning jet aligning the polymer backbones within crystallites orthogonal to the fiber axis, and amorphous chains parallel. It is revealed that this structure forms when anisotropic crystallites, pre-assembled in solution, become oriented along the fiber- a configuration with high charge transport potential. Competitive dissociation of excitons formed in the photoactive nanofibers is recorded, with 95%+ photoluminescence quenching upon electron acceptor introduction. Transient absorption studies reveal that silver nanoparticle addition to the fibers improves charge generation and/or lifetimes. 1 ns post-excitation, the plasmonic architecture contains 45% more polarons, per exciton formed, than the bulk heterojunction. Therefore, enhanced exciton populations may be successfully translated into additional charge carriers.
与传统有机光伏结构相比，纳米纤维活性层能够对分子结构以及电子供体：受体域的尺寸和分布进行分级控制。这种结构是通过静电纺丝半导体聚合物纳米纤维形成供体通道，然后用电子受体渗透来创建的。静电纺丝会诱导链和微晶排列，从而增强光捕获和电荷传输。在此，预测了这些活性层中的电荷传输能力，并评估了电荷分离和动力学，以评估它们的光伏潜力。通过X射线和电子衍射，阐明了纤维纳米结构，静电纺丝射流的单轴伸长使微晶内的聚合物主链与纤维轴正交排列，非晶链平行排列。结果表明，当在溶液中预组装的各向异性微晶沿纤维取向时会形成这种结构——一种具有高电荷传输潜力的构型。记录了在光活性纳米纤维中形成的激子的竞争性解离，引入电子受体后光致发光猝灭率超过95%。瞬态吸收研究表明，向纤维中添加银纳米颗粒可改善电荷产生和/或寿命。激发后1纳秒，与本体异质结相比，等离子体结构每形成一个激子所含的极化子多45%。因此，增强的激子数量可能会成功转化为额外的电荷载流子。
