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Title: Innovative fabrication, characterisation and real-world lifetime study of organic photovoltaic devices
Author: Zhang, Yiwei
ISNI:       0000 0004 6350 2796
Awarding Body: University of Sheffield
Current Institution: University of Sheffield
Date of Award: 2016
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To commercialize organic photovoltaics, some challenges still need to overcome, mainly including developing cost-effective scalable fabrication techniques, investigating strategies to improve device efficiency, increasing lifetime. In the thesis, three issues are investigated. First, the fabrication of organic solar cells via spray coating in air has been presented. High efficiency organic solar cell arrays based on PBDTTT-EFT: PC71BM were fabricated over large area substrate (5 cm × 5 cm) by spray coating in air. An efficiency of 8.06% was demonstrated in devices with both PEDOT:PSS hole transport layer and PBDTTT-EFT:PC71BM active layer spray coated. The spray coating was also used to fabricate zinc oxide electron transport layer and high crystalline polymer: fullerene blends. The devices fabricated with spray coating illustrate comparable efficiency to devices that fabricated by spin coating. Using neutron techniques (neutron reflectivity and small angle neutron scattering), the effects of solvent additive (DIO) and thermal annealing on morphology within a PffBT4T-2OD:PC71BM bulk heterojunction film have been investigated. It has been found that the DIO act as plasticizer and can coarsen the domains within the bulk heterojunction during thermal annealing. This can significantly improve the device efficiency by 20%. Finally, PCDTBT:PC71BM based organic solar cells operation was tracked in real-world condition for a period of one year. It is found the pixels near the edge have reduced stability due to the ingress of water and oxygen through the encapsulation edge. Pixels in the centre of a substrate have enhanced stability, with a Ts80 lifetime of up to 6000 hours. This result suggests with proper encapsulation, organic solar cells can hold pretty good stability under real-world conditions.
Supervisor: Lidzey, David Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available