Inexpensive, abundant, non-toxic thin films for solar cell applications grown by reactive sputtering

The success of CIGS and CdTe solar cells has shown that thin films have the potential to greatly reduce costs while matching the efficiencies of the best silicon devices. As such, a number of new thin film materials that have optimal properties are being explored for solar applications. One of these materials is Cu₂ZnSnS₄ (CZTS), which is composed of entirely abundant and nontoxic elements. Currently, all the processes used to grow this material involve the deposition of metallic/sulfide precursors and a subsequent anneal at high temperature in a H₂S environment to incorporate sulfur into the film. Here we present a novel one-step deposition process where sulfur is incorporated into the film during deposition. Films grown by this process are textured in the (112) direction and show large columnar grains with diameters ranging from 50-500 nm. The best of these films were incorporated into devices and efficiencies as high as 1.5% have been achieved.