An alternative to grid contacts is a transparent conducting oxide (TCO) such as tin oxide (SnO₂). The advantage of TCOs is that they are nearly invisible to incoming light, yet form a good bridge from the semiconductor to the external circuit. TCOs are very useful in manufacturing processes when a glass "superstrate" is used for depositing layers of thin films (such as those of amorphous silicon and cadmium telluride). In this process, the TCO is generally deposited as a thin film on the glass superstrate before the semiconducting layers. These layers are then deposited, followed by a metallic contact that will actually be the bottom of the cell. In this manner, the cell is actually "built" upside down, from the top to the bottom.

But the construction technique isn't the only thing that determines whether a metallic grid or TCO is best for a certain cell design. The "sheet resistance" of the semiconductor is also an important consideration. In crystalline silicon, for example, the semiconductor carries charge (electrons) well enough to reach a finger of the metallic grid. Because the metal conducts electricity better than a TCO does, shadowing losses are less than the losses that would be associated with using a TCO. Amorphous silicon, on the other hand, conducts very poorly in the horizontal direction and therefore benefits from having a TCO over every bit of its surface.

In silicon (a), horizontal electron movement is sufficient to reach a finger of the metallic grid, making the grid contact preferable. Amorphous silicon (b) conducts very poorly in the horizontal direction and therefore benefits from having a TCO layer over its entire surface.