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Document Type

Thesis - University Access Only

Award Date


Degree Name

Master of Science (MS)


Electrical Engineering and Computer Science

First Advisor

David W. Galipeau

Second Advisor

Qiquan Qiao


Organic bulk heterojunction solar cells hold promise as an alternative to traditional silicon solar cells due to lower production cost from reduced material thickness, solution processing and high device performance. The narrow absorption range, low carrier mobility of the photoactive materials and interfacial problems limited high performance devices. There is need for low cost, easily processed, thermally stable, robust and highly efficient recombination layer in tandem polymer solar cells. The objective of this research was to develop a novel all-solution processed tandem polymer solar cell using a recombination layer that is low cost with at least 8% efficiency. In this dissertation, light absorption of the photoactive materials was increased by stacking two cells in a series-connected tandem structure. The recombination layer in the tandem cells was Nb2O5-PEDOT:PSS. Charge extraction at the cathode of the tandem cell consisted of a novel Nb2O5/CsF/Al layers. Nb2O5 nanoparticles were synthesized via solutionprocessing. X-ray diffractometry measurements of the Nb2O5 film showed orthorhombic phase when annealed at 600C. The Nb2O5 film showed transmittance values greater than 80% in the as-prepared and annealed films. The Nb2O5 film showed a thermally stable optical bandgap of 3.6 - 3.7 eV. The photoluminescence spectroscopy of the Nb2O5 film indicated the absence of surface defects and demonstrated charge transfer from the P3HT

Library of Congress Subject Headings

Solar cells
Solar cells -- Reliability


Includes bibliographical references (pages 106-135)



Number of Pages



South Dakota State University


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