Comparative study of conventional and hybrid blocking layers for solid-state dye-sensitized solar cells.

In hybrid solar cells a blocking layer between the transparent electrode and the mesoporous titanium dioxide is used to prevent short-circuits between the hole-conductor and the front electrode. The conventional approach is to use a compact film of titanium dioxide. This layer has to be of optimum thickness: it has to cover the rough surface of the anode material completely while keeping it as thin as possible since the layer acts as an ohmic resistance itself. A competitive alternative arises when using an amphiphilic diblock copolymer as a functional template to produce thin, hybrid films containing a conducting titanium dioxide network embedded in an insulating ceramic material. These hybrid films can be produced much thinner compared to the conventional approach and, hence, they possess a 32% higher conductivity. The conventional and the hybrid blocking layer are characterized by conductive scanning probe microscopy and macroscopic conductance measurements. Additionally, the functionality of both blocking layers in solid-state dye-sensitized solar cells, as tested with current-voltage measurements, is verified.