Poly-Si(O)x passivating contacts for high-efficiency c-Si IBC solar cells

Yang, G.; Zhang, Y.; Procel Moya, P.A.; Weeber, A.W.; Isabella, O.; Zeman, M.

doi:10.1016/j.egypro.2017.09.257

Poly-Si(O)x passivating contacts for high-efficiency c-Si IBC solar cells

Title

Poly-Si(O)x passivating contacts for high-efficiency c-Si IBC solar cells

Author

Yang, G. (TU Delft Photovoltaic Materials and Devices)
Zhang, Y. (TU Delft EKL Processing)
Procel Moya, P.A. (TU Delft Photovoltaic Materials and Devices)
Weeber, A.W. (TU Delft Photovoltaic Materials and Devices)
Isabella, O. (TU Delft Photovoltaic Materials and Devices)
Zeman, M. (TU Delft Electrical Sustainable Energy)

Department

Electrical Sustainable Energy

Date

2017

Abstract

Highest conversion efficiency in crystalline silicon (c-Si) solar cells can be enabled by quenching minority carriers' recombination at c-Si/contact interface owing to carrier-selective passivating contacts. With the semi-insulating poly-crystalline silicon (SIPOS, poly-Si) a very good passivation of c-Si surfaces was obtained. We have explored these passivating structures on IBC solar cells and obtained over 22% efficiency with over 23% within reach on the short term. We present in detail the passivation quality of p-type and n-type ion-implanted LPCVD poly-crystalline silicon (poly-Si) and its relation to the doping profile. Optimized poly-Si layers in the role of emitter and BSF showed excellent passivation (J_0,emitter = 11.5 fA/cm² and J_0,BSF = 4.5 fA/cm²) and have been deployed in FSF-based IBC c-Si solar cells using a simple self-aligned patterning process. Applying an optimized passivation of FSF by PECVD a-Si:H/SiNx layer (J_0,FSF = 6.5 fA/cm²) leads to a cell with efficiency of 22.1% (V_OC = 709 mV, J_SC = 40.7 mA/cm², FF = 76.6%). Since over 83% FF has been reached with adjusted metallization technology on similar IBC structures, we believe 23% efficiency is within reach on the short term. Further improvement, especially at J_SC level, is expected by deploying less absorbing carrier-selective passivating contacts based on poly-Si or wide bandgap poly-SiO_x layers (J₀ ~ 10 fA/cm²).