Development of Solar Cells with Trapezoidal Grid Fingers

In concentrator solar cells, traditional metallic contacts cover a substantial portion of the device area, resulting in reflected light that diminishes the amount of current collected. In this paper, we developed trapezoidal front grid fingers to decrease the optical shadowing and the resulting loss of the device short-circuit current. By using a negative photoresist, a thick metal layer can be deposited by metal evaporation. The formation of an organic and metallic reflective deposit under the negative sloped photoresist is observed, though. By removing this deposit, a similar short-circuit current to typical Ni/Au contacts deposited by electrodeposition is obtained. Even though the Ti/Al grid fingers have larger width, they have the same effective shadowing due to the trapezoidal shape. At high concentration, a higher efficiency is obtained as well due to a high fill factor and improved open circuit voltage.