{"id":2737,"date":"2011-06-23T14:49:54","date_gmt":"2011-06-23T14:49:54","guid":{"rendered":"https:\/\/mtlsites.mit.edu\/annual_reports\/2011\/?p=2737"},"modified":"2011-07-19T15:06:26","modified_gmt":"2011-07-19T15:06:26","slug":"anomalous-singlet-exciton-fission-magnetic-field-effect-in-diphenyltetracene-c60-solar-cells","status":"publish","type":"post","link":"https:\/\/mtlsites.mit.edu\/annual_reports\/2011\/anomalous-singlet-exciton-fission-magnetic-field-effect-in-diphenyltetracene-c60-solar-cells\/","title":{"rendered":"Anomalous Singlet Exciton Fission Magnetic Field Effect in Diphenyltetracene-C<sub>60<\/sub> Solar Cells"},"content":{"rendered":"<div class=\"pf-content\"><p>Singlet exciton fission may find application in more efficient solar cells. Fission can reduce thermalization losses because by splitting the exciton, a high energy photon can produce two charge carrier pairs instead of one. The two device implementations to date that exploit singlet exciton fission, a pentacene photodetector and a tetracene solar cell, produce more current by multiplying the number of excitons in the visible part of the spectrum<sup> [<a href=\"#footnote_0_2737\" id=\"identifier_0_2737\" class=\"footnote-link footnote-identifier-link\" title=\"J. Lee, P. Jadhav, and M. A. Baldo, &ldquo;High efficiency organic multilayer photodetectors based on singlet exciton fission,&rdquo; Applied Physics Letters, vol. 95, pp. 033301-033303, July 2009\">1<\/a>] <\/sup><sup> [<a href=\"#footnote_1_2737\" id=\"identifier_1_2737\" class=\"footnote-link footnote-identifier-link\" title=\"P. J. Jadhav, A. Mohanty, J. Sussman, and M. A. Baldo, &ldquo;Singlet exciton fission in nanostructured organic solar cells,&rdquo; Nano Letters, DOI: 10.1021\/nl104202j.\">2<\/a>] <\/sup>. In this work we show that diphenyltetracene (DPT) also exhibits singlet exciton fission; in Figure 1 we present a DPT-C<sub>60<\/sub> device in which singlet exciton fission contributes negatively to the current, which is opposite behavior to the previous two implementations.<\/p>\n<p>DPT differs from previous implementations of singlet exciton fission in that its triplet <em>E<sub>t<\/sub><\/em> = 1.2eV<sup> [<a href=\"#footnote_2_2737\" id=\"identifier_2_2737\" class=\"footnote-link footnote-identifier-link\" title=\"C. Burgdorff, T. Kircher, and H. G. L&ouml;hmannsr&ouml;ben, &ldquo;Photophysical properties of tetracene derivatives in solution,&rdquo; Spectrochimica Acta Part A: Molecular Spectroscopy vol. 44, pp. 1137-1141, Apr. 1988.\">3<\/a>] <\/sup> is less than the energy of the DPT-C<sub>60 <\/sub>charge transfer state (CT) <em>E<sub>CT<\/sub><\/em> = 1.25eV. Hence the triplets cannot break up to form charge carriers. This effect is seen in the positive magnetic field effect shown in Figure 2. The application of a magnetic field results in reduced singlet fission and hence an increase in the number of singlet excitons and thereby increased current. In contrast, a similar measurement with a lower CT energy yields the usual negative magnetic field dependence. For example, below we demonstrate a negative magnetic field effect in DPT-F<sub>16<\/sub>CuPC, where F<sub>16<\/sub>CuPC is fluorinated copper phthalocyanine.<\/p>\n<p>The amorphous nature of the DPT film in the device results in an isotropic magnetic field effect. Consequently, the large magnetic field effect shown by the device, 5% at .45T, may be used in an isotropic magnetic field detector.<\/p>\n\n\t\t<style type=\"text\/css\">\n\t\t\t#gallery-1 {\n\t\t\t\tmargin: auto;\n\t\t\t}\n\t\t\t#gallery-1 .gallery-item {\n\t\t\t\tfloat: left;\n\t\t\t\tmargin-top: 10px;\n\t\t\t\ttext-align: center;\n\t\t\t\twidth: 50%;\n\t\t\t}\n\t\t\t#gallery-1 img {\n\t\t\t\tborder: 2px solid #cfcfcf;\n\t\t\t}\n\t\t\t#gallery-1 .gallery-caption {\n\t\t\t\tmargin-left: 0;\n\t\t\t}\n\t\t\t\/* see gallery_shortcode() in wp-includes\/media.php *\/\n\t\t<\/style>\n\t\t<div id='gallery-1' class='gallery galleryid-2737 gallery-columns-2 gallery-size-thumbnail'><dl class='gallery-item'>\n\t\t\t<dt class='gallery-icon landscape'>\n\t\t\t\t<a href='https:\/\/mtlsites.mit.edu\/annual_reports\/2011\/wp-content\/blogs.dir\/10\/files\/2011\/06\/jadhav_singlet-fission_01.jpg' rel=\"lightbox[2737]\"><img width=\"130\" height=\"130\" src=\"https:\/\/mtlsites.mit.edu\/annual_reports\/2011\/wp-content\/blogs.dir\/10\/files\/2011\/06\/jadhav_singlet-fission_01-150x150.jpg\" class=\"attachment-thumbnail size-thumbnail\" alt=\"Figure 1: Device structures for the DPT-C60 and the DPT- F16CuPC devices.\" loading=\"lazy\" aria-describedby=\"gallery-1-2738\" \/><\/a>\n\t\t\t<\/dt>\n\t\t\t\t<dd class='wp-caption-text gallery-caption' id='gallery-1-2738'>\n\t\t\t\tFigure 1: Device structures for the DPT-C<sub>60<sub> and the DPT- F<sub>16<\/sub>CuPC devices. \n\t\t\t\t<\/dd><\/dl><dl class='gallery-item'>\n\t\t\t<dt class='gallery-icon landscape'>\n\t\t\t\t<a href='https:\/\/mtlsites.mit.edu\/annual_reports\/2011\/wp-content\/blogs.dir\/10\/files\/2011\/06\/jadhav_singlet-fission_02.jpg' rel=\"lightbox[2737]\"><img width=\"130\" height=\"130\" src=\"https:\/\/mtlsites.mit.edu\/annual_reports\/2011\/wp-content\/blogs.dir\/10\/files\/2011\/06\/jadhav_singlet-fission_02-150x150.jpg\" class=\"attachment-thumbnail size-thumbnail\" alt=\"Figure 2\" loading=\"lazy\" aria-describedby=\"gallery-1-2739\" \/><\/a>\n\t\t\t<\/dt>\n\t\t\t\t<dd class='wp-caption-text gallery-caption' id='gallery-1-2739'>\n\t\t\t\tFigure 2: Magnetic field effect on photocurrent in the DPT-C<sub>60<\/sub> and the DPT- F<sub>16<\/sub>CuPC devices. 500 nm is a DPT absorption peak. Also shown is the magnetic effect on DPT fluorescence, which is a signature of singlet fission.\n\t\t\t\t<\/dd><\/dl><br style=\"clear: both\" \/>\n\t\t<\/div>\n\n<\/div><ol class=\"footnotes\"><li id=\"footnote_0_2737\" class=\"footnote\">J. Lee, P. Jadhav, and M. A. Baldo, \u201cHigh efficiency organic multilayer photodetectors based on singlet exciton fission,\u201d <em>Applied Physics Letters<\/em>, vol. 95, pp. 033301-033303, July 2009 [<a href=\"#identifier_0_2737\" class=\"footnote-link footnote-back-link\">&#8617;<\/a>]<\/li><li id=\"footnote_1_2737\" class=\"footnote\">P. J. Jadhav, A. Mohanty, J. Sussman, and M. A. Baldo, \u201cSinglet exciton fission in nanostructured organic solar cells,\u201d <em>Nano Letters<\/em>, <strong>DOI: <\/strong>10.1021\/nl104202j. [<a href=\"#identifier_1_2737\" class=\"footnote-link footnote-back-link\">&#8617;<\/a>]<\/li><li id=\"footnote_2_2737\" class=\"footnote\">C. Burgdorff, T. Kircher, and H. G. L\u00f6hmannsr\u00f6ben, &#8220;Photophysical properties of tetracene derivatives in solution,\u201d <em>Spectrochimica Acta Part A: Molecular Spectroscopy<\/em> vol. 44, pp. 1137-1141, Apr. 1988. [<a href=\"#identifier_2_2737\" class=\"footnote-link footnote-back-link\">&#8617;<\/a>]<\/li><\/ol>","protected":false},"excerpt":{"rendered":"<p>Singlet exciton fission may find application in more efficient solar cells. Fission can reduce thermalization losses because by splitting the&#8230;<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"closed","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":[],"categories":[6,5532],"tags":[40,4116],"_links":{"self":[{"href":"https:\/\/mtlsites.mit.edu\/annual_reports\/2011\/wp-json\/wp\/v2\/posts\/2737"}],"collection":[{"href":"https:\/\/mtlsites.mit.edu\/annual_reports\/2011\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/mtlsites.mit.edu\/annual_reports\/2011\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/mtlsites.mit.edu\/annual_reports\/2011\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/mtlsites.mit.edu\/annual_reports\/2011\/wp-json\/wp\/v2\/comments?post=2737"}],"version-history":[{"count":5,"href":"https:\/\/mtlsites.mit.edu\/annual_reports\/2011\/wp-json\/wp\/v2\/posts\/2737\/revisions"}],"predecessor-version":[{"id":3995,"href":"https:\/\/mtlsites.mit.edu\/annual_reports\/2011\/wp-json\/wp\/v2\/posts\/2737\/revisions\/3995"}],"wp:attachment":[{"href":"https:\/\/mtlsites.mit.edu\/annual_reports\/2011\/wp-json\/wp\/v2\/media?parent=2737"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/mtlsites.mit.edu\/annual_reports\/2011\/wp-json\/wp\/v2\/categories?post=2737"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/mtlsites.mit.edu\/annual_reports\/2011\/wp-json\/wp\/v2\/tags?post=2737"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}