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Synergistic photocurrent addition in hybrid quantum dot: Bulk heterojunction solar cells
Kim, Gi-Hwan,Walker, Bright,Zhitomirsky, David,Heo, Jungwoo,Ko, Seo-Jin,Park, Jongnam,Sargent, Edward H.,Young Kim, Jin Elsevier 2015 Nano energy Vol.13 No.-
<P><B>Abstract</B></P> <P>We investigate the effect of a thin PbS quantum dot (QD) layer on the performance of hybrid quantum-dot-organic solar cells (QD-OSCs). The PbS QD layer is able to function as a photosensitizing layer to improve short circuit current density (<I>J</I> <SUB>SC</SUB>) and power conversion efficiency (PCE) by exploiting solar flux in the near infrared region up to 1100nm. The increase in <I>J</I> <SUB>SC</SUB> is well represented by changes observed in the external quantum efficiency of devices with and without the PbS QD layer, including the region of the first exciton transition where only the PbS QD layer absorbs. Remarkably, enhanced performance was observed in QD-OSCs consisting of just a 13nm thick PbS QD layer and 150nm PTB7:PC<SUB>71</SUB>BM layer, exhibiting a <I>J</I> <SUB>SC</SUB> of 17.0mAcm<SUP>−2</SUP>, and PCE of 8.30% (8.58% for champion device) compared to reference devices without PbS QD which produced a <I>J</I> <SUB>SC</SUB> of 15.4mAcm<SUP>−2</SUP> and PCE of 7.56%.</P> <P><B>Highlights</B></P> <P> <UL> <LI> We have fabricated hybrid solar cells using a PbS QD layer and PTB7/PC<SUB>71</SUB>BM layer. </LI> <LI> The device is built on PTB7:PC<SUB>71</SUB>BM bulk heterojunction and a PbS QD layer. </LI> <LI> The PbS QD layer acts as a photosensitizing layer to improve the device performance. </LI> <LI> Additional photocurrent leads to enhancement in performance in hybrid solar cells. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>The effect of a thin PbS quantum dot (QD) layer on the performance of hybrid quantum-dot-organic solar cells (QD-OSCs) was investigated. The PbS QD layer is able to function as a photosensitizing layer with PTB7/PC<SUB>71</SUB>BM bulk heterojunction to improve short circuit current density from 15.4mAcm<SUP>−2</SUP> to 17.0mAcm<SUP>−2</SUP> and power conversion efficiency from 7.56% to 8.30%. </P> <P>[DISPLAY OMISSION]</P>
Spiral density waves in a young protoplanetary disk
Pé,rez, Laura M.,Carpenter, John M.,Andrews, Sean M.,Ricci, Luca,Isella, Andrea,Linz, Hendrik,Sargent, Anneila I.,Wilner, David J.,Henning, Thomas,Deller, Adam T.,Chandler, Claire J.,Dullemond, American Association for the Advancement of Scienc 2016 Science Vol.353 No.6307
<P>Gravitational forces are expected to excite spiral density waves in protoplanetary disks, disks of gas and dust orbiting young stars. However, previous observations that showed spiral structure were not able to probe disk midplanes, where most of the mass is concentrated and where planet formation takes place. Using the Atacama Large Millimeter/submillimeter Array, we detected a pair of trailing symmetric spiral arms in the protoplanetary disk surrounding the young star Elias 2-27. The arms extend to the disk outer regions and can be traced down to the midplane. These millimeter-wave observations also reveal an emission gap closer to the star than the spiral arms. We argue that the observed spirals trace shocks of spiral density waves in the midplane of this young disk.</P>