Enhanced performance of layer-evolved bulk-heterojunction solar cells with Ag nanoparticles by sequential deposition

Abstract

Organic photovoltaic devices based on layer-evolved bulk-heterojunction (LE-BHJ) from poly{[4,4'-bi s(2-ethylhexyl) dithieno(3,2-b:2',3'-d) silole]-2,6-diyl-alt-[4,7-bis(2-thienyl)-2,1,3-benzothiadiazole]-5, 5'-diyl} (Si-PCPDTBT)/[6,6]-phenyl C-71 butyric acid methyl ester (PC71BM) are successfully fabricated by a sequential solution deposition process. During the process of a top layer being deposited from an appropriate cosolvent ratio control, the top layer of PC71BM vertically penetrates a pre-coated layer of Si-PCPDTBT, resulting in an inter-diffused nanostructure with an LE-BHJ surface morphology. The LE-BHJ cells exhibit improved nanoscale phase separation and comparable performance, in comparison with the conventional BHJ device. Furthermore, Ag nanoparticles (NPs) with optimized ratio embedded LE-BHJ exhibit significant enhanced efficiency in comparison with the conventional BHJ and pristine LE-BHJ devices, because the multiple scattering from the Ag NPs leads to longer optical paths, which give rise to effective absorptivity and reduced leakage current within the BHJ active film. (C) 2015 Elsevier B. V. All rights reserved.