{"id":304,"date":"2024-10-23T15:15:18","date_gmt":"2024-10-23T15:15:18","guid":{"rendered":"https:\/\/seegroup.mit.edu\/?page_id=304"},"modified":"2025-06-07T19:50:23","modified_gmt":"2025-06-07T19:50:23","slug":"organic-semiconductors","status":"publish","type":"page","link":"https:\/\/seegroup.mit.edu\/index.php\/organic-semiconductors\/","title":{"rendered":"Organic Semiconductors"},"content":{"rendered":"

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Research: Measuring and Controlling Exciton Spin in Organic Semiconductors<\/strong><\/h2>\n

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M. Segal and M.A. Baldo<\/span>
<\/span><\/p>\n

Sponsorship: NSF, MRSEC and 3M<\/span>
Collaborators: Joseph Shinar, Iowa State University; Zoltan Soos, Princeton University; Troy Van Voorhis, MIT Chemistry Department<\/span><\/p>\n

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Main Research Areas<\/p>\n

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Solar Cells<\/a><\/p>\n

Light Emitting Devices<\/a><\/p>\n

Algorithms for Engineering System Design<\/a><\/p>\n

Magnetic Domain Wall Devices<\/a><\/p>\n<\/div>\n<\/div>\n

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Introduction<\/strong><\/h4>\n

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Organic light emitting devices (OLEDs) are perhaps the most important application of organic semiconductors. OLEDs can be understood as machines that convert injected charges into excitons. An exciton is a molecular excited state that mediates the emission of light. Each exciton may take may one four possible spin states: three \u201ctriplet\u201d states of total spin 1, or one \u201csinglet\u201d state of total spin 0. The ground state is also a singlet in the vast majority of molecules. Thus, the efficiency of radiation from an exciton is typically spin-dependent. The decay of the singlet exciton is allowed, yielding radiation known as fluorescence. The decay of the triplet exciton is usually disallowed. When it occurs at all, radiation from triplet states is slow and known as phosphorescence.<\/span><\/p>\n

‘Extrafluorescence’ is perhaps the most important result. We have demonstrated the ability to manipulate the fraction of excitons which form as singlets in fluorescent materials by altering the OLED structure. We have built a fluorescent OLED showing an approximately three-fold increase in singlet fraction and fluorescent efficiency. Extrafluorescence may help address the challenge of producing efficient, stable and saturated blue light with organic semiconductors.<\/span><\/p>\n

We are concerned with the fraction of singlet excitons, \u03c7, which determines the fundamental efficiency limit of fluorescent OLEDs. Our work has had four major outcomes:<\/span><\/p>\n

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