Singlet exciton fission, a multi-exciton generation process, in organic semiconductor solar cells

Organic semiconductor photovoltaics hold the promise of cheap production and low manufacturing setup costs. The highest efficiency seen in research labs, ~10% today, is still too low for production. In this work we explore implementations of a multiple exciton generation process, singlet exciton fission, to work around the Shockley-Queisser limit, according to which, all single junctions cells have a theoretical efficiency limit of 33.7%. This is the first implementation of a singlet fission photovoltaic. We measured a singlet fission efficiency of 72% at room temperature. We showed that singlet fission can be implemented in bulk heterojunction photovoltaics, which is an important result since some of the highest efficiency organic photovoltaics in the last 5 years have been bulk heterojunction structures. Secondly, we showed that the magnetic field effect can be used as a probe to investigate triplet dissociation in singlet fission devices. Thirdly, we implemented singlet fission photovoltaics, using the singlet fission material pentacene as donor and low bandgap infrared-absorptive lead chalcogenide quantum dots as acceptors. Singlet fission can enhance the efficiency of organic photovoltaics only if the fission material is paired with an absorptive low-energy-gap material. We find that pentacene triplet excitons dissociate at the pentacene/quantum dot heterojunctions with an internal quantum efficiency of 35%. Lastly, we investigate a series of materials to find a better acceptor in singlet fission photovoltaics using the methods and some results from the previous two investigations. We investigate device structures that pair pentacene and 6,13 diphenyl-pentacene as singlet fission donors with C60 , perylene diimides, PbS quantum dots and PbSe quantum dots as acceptors.

Department dc:contributor.department

Massachusetts Institute of Technology. Dept. of Electrical Engineering and Computer Science.

Grantor dc:publisher

Massachusetts Institute of Technology

Year dc:date.issued

2012

Author dc:creator

• Jadhav, Priyadarshani

Advisor dc:contributor.advisor

• Marc A. Baldo.

• Electrical Engineering and Computer Science.

Statement dc:rights

• M.I.T. theses are protected by copyright. They may be viewed from this source for any purpose, but reproduction or distribution in any format is prohibited without written permission. See provided URL for inquiries about permission.

Licence dc:rights.uri

• http://dspace.mit.edu/handle/1721.1/7582

Language dc:language.iso

eng

Handle dc:identifier.uri

http://hdl.handle.net/1721.1/75635

OAI identifier oai:identifier

oai:dspace.mit.edu:1721.1/75635