Technology and Operating Principles of Silicon-based Heterojunction Solar Cells (TopShot)

The combination of amorphous/crystalline silicon (a-Si:H/c-Si) heterojunctions (SHJ)  and back-contacted back-junction solar cell concepts offers a very high efficiency potential of 24%. Solar cells with a-Si:H/c-Si heterojunctions have proven open circuit voltage values exceeding 740 mV (Mishima et al.). Back-contacted cell architectures allow for the avoidance of contact shading losses. Furthermore optical losses in the front a-Si:H layer and front transparent conductive oxide as present in both-sides-contacted SHJ solar cells can be circumvented.

One objective of the project TopShot is to develop appropriate contact systems including amorphous silicon layers, transparent conductive oxides and/or metal. Furthermore patterning processes for these layers, that are compatible with the high passivation quality of the a-Si/c-Si interface are investigated. These components are tested on small area solar cells in a first step, and subsequently upscaling of the area is addressed.

Example for back-contacted silicon heterojunction solar cell („PRECASH“, Stangl et al.)

References

N. Mingirulli, J. Haschke, R. Gogolin, R. Ferré, T.F. Schulze, J. Düsterhöft, N.-P. Harder, L. Korte, R. Brendel, B. Rech, Efficient interdigitated back-contacted silicon heterojunction solar cells,
Phys. Status Solidi RRL 5, No. 4, 159–161 (2011) / DOI 10.1002/pssr.201105056

R. Stangl, J. Haschke, M. Bivour, L. Korte, M. Schmidt, K. Lips, B. Rech,  Planar rear emitter back contact silicon heterojunction solar cells,
Solar Energy Materials and Solar Cells 93 (2009), p. 1900-1903, doi:10.1016/j.solmat.2009.06.010