Multifunctional Role of Nanostructured CdS Interfacial Layers in Hybrid Solar Cells

We demonstrate here a multifunctional application of CdS layers with nanotextured and nanowire morphology in four types of hybrid solar cells, i.e., (i) nanocrystal-polymer cell, (ii) nanocrystal-organic donor-acceptor bulk heterojunction (BHJ) inverted cell, (iii) nanocrystal-dye sensitized solid state cell and (iv) nanocrystal-dye sensitized electrochemical cell. The role of CdS layer in each type of the above cells has been elucidated and the photovoltaic (PV) performance of the PV cells has been compared. It is shown that CdS acts as acceptor in the cells of types (i) and (iii), while it plays the role of an electron-selective (hole-blocking) layer to direct electrons from the organic counterpart to anode in the cases (ii) and (iv). Morphology of the CdS layer makes a noticeable effect on the PV performance. In particular, the nanowire array demonstrated an improved efficiency of collection of charge carriers as compared with the continuous textured surface due to the increased organic-CdS interface area in PV cells of practically all types. It is demonstrated that the same nanocrystal-dye structure can operate either as PV cell of type (iii) or PV cell of type (iv).