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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

Qiquan Qiao


Organic photovoltaic (OPV) technology has drawn much attention during the past few decades due to its role to role processability, compatibility with flexible substrates and low manufacturing cost. However, one of the major drawbacks of OPV technology is narrow absorption width which limits device performance. To absorb solar energy more efficiently, multi-junction polymer solar cells are used where two or more subcells are stacked together. There are several challenges in developing multi-junction polymer solar cells. These include selection of proper absorber layers and fabrication of robust, transparent, conductive interfacial layer to connect the subcells. The goal of this work was to develop a low temperature processable interconnect layer for solution processed tandem and triple junction polymer solar cells with high efficiency. Different characterization techniques were carried out to find the optimum interfacial conditions to connect the top and bottom cells. The experimental results show that surface morphology of PEDOT:PSS in interconnecting layer (ICL) impacts overall tandem device performance. The annealing temperature for the ICL (PEDOT:PSS/AZO/PEIE) was also investigated. The new ICL was used to successfully connect the top and bottom cells in double junction polymer solar cells without major losses. A triple junction polymer solar cell was also fabricated using the same ICL where identical polymer (P3HT) was used in top, middle and bottom layers. Double junction Voc of 1.05 V and triple junction Voc of 1.4 V indicated that the ICLs worked xiv effectively. However, triple junction solar cells exhibited poor device performance. The Jsc of triple junction polymer solar cells was low due to the use of the same polymer in top, middle and bottom cells. FF and Voc of triple junction polymer solar cells were improved by optimizing the thickness of active layer.

Library of Congress Subject Headings

Solar cells
Solar cells--Design and construction


Includes bibliographical references (pages 71-75)



Number of Pages



South Dakota State University


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