Binary Semiconductor Metal Oxide as Photoanodes

In DSSC, charge carrier recombination is the major problem for achieving the lower PCE. Presently, researchers were more concentrated on mixed metal oxide nanostructures in the form of alloys, nanocomposites, and core shells. Among these techniques, formation of metal oxide core shell nanostructures was the more efficient way to enhancing the PCE due to some admirable properties. In this context, we proposed ZnO, TiO 2 , SnO 2 , and ZrO 2 ‐based core shell systems and their advantages. In core shell, the improvement of the PCE was attributed to the increase in the J SC , V OC , and fill factor, and these results suggested that electron injection is more efficient through the shell compared with the uncoated cell. There the two possible mechanisms are the major reason for the increased V OC such as “blocking effects” and “surface dipole effects.” Means such as the coating layer act as a blocking barrier for the recombination of the injected electrons either with the oxidized dye or with the oxidized redox couple. If the recombination of the injected electrons is reduced, the electron population at the photo‐anode conduction band will be increased, hence resulting in a quasi‐Fermi level increase, and as a result V OC is increased. Another possible mechanism is “surface dipole effect” which is not related directly to the electron recombination. The coating layer may induce the positive charges near the surface resulting in an electrostatic field that will be generated, which could increase the conduction edge, hence the V OC is increased. For these reasons, the formation of the mixed metal oxide nanostructure enhanced the performance of the DSSCs. Hence, finally it is concluded that mixed metal oxide incorporated photo‐anodes plays a vibrant role for enhancing the PCE.