Hybrid Solar Cells Based on CdS Nanowire Arrays

Abstract

Three types of hybrid solar cells based on CdS nanowire crystals have been prepared, i.e., (i) nanocrystal - polymer, (ii) nanocrystal - dye and (iii) nanocrystal - organic donor-acceptor bulk heterojunction (BHJ), and the role of CdS layer in each of the above structures has been elucidated. It has been found that CdS plays the active role of acceptor in the first two types of solar cells, whereas it plays the role of an electron-transporting (hole-blocking) layer to rectify electron flow from the organic donor-acceptor BHJ to anode in the case (iii). By changing morphology of the CdS layer from a textured continuous film to a nanowire array we demonstrate an improved efficiency of collection of charge carriers due to the increased organic-CdS interface area. Overall, a bifunctional role of the CdS nanostructured layer as a bottom electrode with a high electron affinity and as a means to increase a hybrid interface for better electron collection from the organic active layer has been demonstrated.