Reduced Recombination in High Efficiency Molecular Nematic Liquid Crystalline: Fullerene Solar Cells

被引:62
作者
Armin, Ardalan [1 ,2 ]
Subbiah, Jegadesan [3 ]
Stolterfoht, Martin [1 ,2 ]
Shoaee, Safa [1 ,2 ]
Xiao, Zeyun [3 ]
Lu, Shirong [3 ]
Jones, David J. [3 ]
Meredith, Paul [1 ,2 ]
机构
[1] Univ Queensland, Sch Math & Phys, COPE, Brisbane, Qld 4072, Australia
[2] Univ Queensland, Sch Chem & Mol Biosci, Brisbane, Qld 4072, Australia
[3] Univ Melbourne, Inst Bio21, Sch Chem, 30 Flemington Rd, Parkville, Vic 3010, Australia
关键词
bimolecular recombination; bulk heterojunction solar cells; charge transfer state; non-Langevin; solar cells; NON-LANGEVIN RECOMBINATION; BIMOLECULAR RECOMBINATION; QUANTUM EFFICIENCY; CHARGE-TRANSPORT; GEMINATE; MOBILITY;
D O I
10.1002/aenm.201600939
中图分类号
O64 [物理化学(理论化学)、化学物理学];
学科分类号
070304 ; 081704 ;
摘要
Bimolecular recombination in bulk heterojunction organic solar cells is the process by which nongeminate photogenerated free carriers encounter each other, and combine to form a charge transfer (CT) state which subsequently relaxes to the ground state. It is governed by the diffusion of the slower and faster carriers toward the electron donor-acceptor interface. In an increasing number of systems, the recombination rate constant is measured to be lower than that predicted by Langevin's model for relative Brownian motion and the capture of opposite charges. This study investigates the dynamics of charge generation, transport, and recombination in a nematic liquid crystalline donor:fullerene acceptor system that gives solar cells with initial power conversion efficiencies of >9.5%. Unusually, and advantageously from a manufacturing perspective, these efficiencies are maintained in junctions thicker than 300 nm. Despite finding imbalanced and moderate carrier mobilities in this blend, strongly suppressed bimolecular recombination is observed, which is approximate to 150 times less than predicted by Langevin theory, or indeed, more recent and advanced models that take into account the domain size and the spatial separation of electrons and holes. The suppressed bimolecular recombination arises from the fact that ground-state decay of the CT state is significantly slower than dissociation.
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页数:10
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