Ganzer Lucia, Zappia Stefania, Russo Mattia, Ferretti Anna Maria, Vohra Varun, Diterlizzi Marianna, Antognazza Maria Rosa, Destri Silvia, Virgili Tersilla
IFN-CNR, Dipartimento di Fisica, Politecnico di Milano, Milano I-20132, Italy.
Istituto di Scienze e Tecnologie Chimiche "Giulio Natta" (SCITEC), Consiglio Nazionale delle Ricerche (CNR), Milano I-20133, Italy.
Phys Chem Chem Phys. 2020 Nov 25;22(45):26583-26591. doi: 10.1039/d0cp05478j.
Using ultrafast spectroscopy, we investigate the photophysics of water-processable nanoparticles composed of a block copolymer electron donor and a fullerene derivative electron acceptor. The block copolymers are based on a poly[2,6-(4,4-bis-(2-ethylhexyl)-4H-cyclopenta[2,1-b;3,4-b']dithiophene)-alt-4,7-(2,1,3-benzothiadiazole)] rod, which is covalently linked with 2 or 100 hydrophilic coil units. In both samples the photogenerated excitons in the blend nanoparticles migrate in tens of ps to a donor/acceptor interface to be separated into free charges. However, transient absorption spectroscopy indicates that increasing the coil length from 2 to 100 units results in the formation of long living charge transfer states which reduce the charge generation efficiency. Our results shed light on the impact of rod-coil copolymer coil length on the blend nanoparticle morphology and provide essential information for the design of amphiphilic rod-coil block copolymers to increase the photovoltaic performances of water-processable organic solar cell active layers.
我们使用超快光谱技术研究了由嵌段共聚物电子供体和富勒烯衍生物电子受体组成的可水加工纳米粒子的光物理性质。这些嵌段共聚物基于聚[2,6-(4,4-双-(2-乙基己基)-4H-环戊并[2,1-b;3,4-b']二噻吩)-alt-4,7-(2,1,3-苯并噻二唑)]棒，其与2个或100个亲水性线圈单元共价连接。在这两个样品中，共混纳米粒子中的光生激子在几十皮秒内迁移到供体/受体界面，被分离成自由电荷。然而，瞬态吸收光谱表明，将线圈长度从2个单元增加到100个单元会导致形成长寿命的电荷转移态，从而降低电荷产生效率。我们的结果揭示了棒-线圈共聚物线圈长度对共混纳米粒子形态的影响，并为设计两亲性棒-线圈嵌段共聚物以提高可水加工有机太阳能电池活性层的光伏性能提供了重要信息。
