Amorphous Silicon Passivation of Aluminum Contacts to n-Type Crystalline Silicon

Ultimately, high efficiency solar cells necessitate a high passivation quality of all surfaces and interfaces. It is known from literature that passivated contacts increase the open circuit voltage by using a tunneling mechanism through a thin insulating layer. In comparison to these concepts we use a bi-layer of intrinsic and phosphorous doped amorphous Si as passivation and tunneling layer. In this paper, we are presenting the successful implementation of an industrially feasible process sequence including a passivation and contacting coating by using conventional PECVD and PVD processes. The most favorable i-/n-a-Si:H and Al PVD deposition conditions were identified. Surprisingly, our experiments showed no clear dependence of the phosphine flow to the passivation quality. However, only the structures with the highest n-type doping of the doped a-Si:H layer results in contact . Photoluminescence images show a drop by half of the PL count intensity after the Al metallization. This indicates that the passivation property of the amorphous silicon is mostly retained.