{"id":1405,"date":"2010-11-25T16:48:17","date_gmt":"2010-11-25T16:48:17","guid":{"rendered":"http:\/\/www.joswassink.nl\/insight\/?p=1405"},"modified":"2010-11-25T16:48:17","modified_gmt":"2010-11-25T16:48:17","slug":"connecting-the-dots","status":"publish","type":"post","link":"https:\/\/www.joswassink.nl\/insight\/?p=1405","title":{"rendered":"Connecting the dots"},"content":{"rendered":"<p><strong>Layers of quantum dots can be used as solar cells. Better connections  between the dots are needed however to boost the efficiency.<\/strong><\/p>\n<div id=\"attachment_1406\" style=\"width: 490px\" class=\"wp-caption aligncenter\"><a rel=\"attachment wp-att-1406\" href=\"http:\/\/www.joswassink.nl\/insight\/?attachment_id=1406\"><img loading=\"lazy\" decoding=\"async\" aria-describedby=\"caption-attachment-1406\" class=\"size-full wp-image-1406\" title=\"pepette_quantum\" src=\"http:\/\/www.joswassink.nl\/insight\/wp-content\/uploads\/2010\/11\/pepette_quantum.jpg\" alt=\"\" width=\"480\" height=\"229\" \/><\/a><p id=\"caption-attachment-1406\" class=\"wp-caption-text\">Ilustration: Elise Talgorn<\/p><\/div>\n<p>They come in all colours. Nano-sized semiconductor crystals,  endearingly called quantum dots or q-dots, manifest properties between  those of molecular matter and bulk material. The reason is that an  electron in a q-dot experiences quantum confinement. This results in  discrete steps between energy states (bandgaps), which depend on the  material as well as the size. Hence, by varying the size of the q-dots  one can tune them to a specific colour, rendering them interesting  candidates for use in solar cells.<!--more--><\/p>\n<p>In her PhD research, Elise  Talgorn (MSc, Applied Sciences) has coated glass substrates with layers  of quantum dots and tested their conductivity. To do this, she had to  get rid of the insulating molecules surrounding the dots, because these  kept the dots so far apart that electrons couldn&#8217;t move from one dot to  the next. By chemically replacing these long molecules with shorter  ones, Talgorn succeeded in increasing the charge carrier mobility by a  factor 500 or so. Simply drying the layers (&#8217;thermal annealing&#8217;)  increased the mobility even more (up to 10,000 times), but the outcome  proved to be less controllable.<\/p>\n<p>Recombination presents another  challenge to using q-dots in solar cells. When a photon hits a q-dot, it  creates a free electron and a &#8216;hole&#8217;; but wait a few nanoseconds and  they simply recombine, as if nothing had happened. For an external  current to be generated, one needs to apply an electric field to draw  the electron-hole pair apart. Talgorn did this by combining cadmium  selenium q-dots (which attract electrons) and cadmium tellurium q-dots  that attract the holes. This could be the working principle for a new  type of solar cell.<\/p>\n<p><em>Elise Talgorn, Photoconductivity of  quantum dot films, 30 November 2010, PhD supervisor Professor Laurens  Siebbeles.<\/em><\/p>\n","protected":false},"excerpt":{"rendered":"<p>Layers of quantum dots can be used as solar cells. Better connections between the dots are needed however to boost the efficiency.<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[3,6],"tags":[348,350,397],"class_list":["post-1405","post","type-post","status-publish","format-standard","hentry","category-articles","category-delta","tag-q-dots","tag-quantumdots","tag-solar-cell"],"_links":{"self":[{"href":"https:\/\/www.joswassink.nl\/insight\/index.php?rest_route=\/wp\/v2\/posts\/1405","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.joswassink.nl\/insight\/index.php?rest_route=\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.joswassink.nl\/insight\/index.php?rest_route=\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.joswassink.nl\/insight\/index.php?rest_route=\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/www.joswassink.nl\/insight\/index.php?rest_route=%2Fwp%2Fv2%2Fcomments&post=1405"}],"version-history":[{"count":0,"href":"https:\/\/www.joswassink.nl\/insight\/index.php?rest_route=\/wp\/v2\/posts\/1405\/revisions"}],"wp:attachment":[{"href":"https:\/\/www.joswassink.nl\/insight\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=1405"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.joswassink.nl\/insight\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=1405"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.joswassink.nl\/insight\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=1405"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}