Efficiency enhancement in organic solar cells by configuring hybrid interfaces with narrow bandgap PbSSe nanocrystals

We hereby present an incorporation technique for inorganic nanocrystals (NCs) in organic solar cells (OSCs) for the improvement of power conversion efficiency (PCE). Ternary PbSSe NCs constitute stable conformations with regular poly(3-hexylthiophene):phenyl-C-70 butyric acid methyl ester (P3HT:PCBM) organic composites under two heterojunction systems, and significant solar performance modification was obtained, depending on the incorporation type. Bilayer heterojunction (Bi-HJ) SCs, in which a pristine NC layer is sandwiched between the organic composite and cathode, showed significantly broadened photon-harvesting resulting from combination of both layers and energetic carrier transport as a result of reduced recombination losses. In contrast, bulk heterojunction (BHJ) SCs comprising combined composites of P3HT:PCBM:NCs in a single layer suffered from inefficient charge transport as a result of ubiquitous charge traps. Use of Bi-HJ cells with an NC layer of optimal thickness greatly enhanced the short-circuit current (J(SC)) to 10.54 mA cm (2) and a PCE of 3.12% was achieved; this is a 31% improvement over the conversion efficiency of purely organic cells without NCs. The separate PbSSe NC layer coupled well with the organic composite to provide a broad-range photon-harvesting ability and vertically efficient interfacial junctions for systematic charge transport; this greatly enhances the photovoltaic performances of the OSCs. (C) 2012 Elsevier B. V. All rights reserved.