Low-temperature aluminum doped and induced polysilicon and its application as partial rear contacts on p-type silicon solar cells

Low-temperature contact techniques offer benefits for various solar cells, including tandem solar cells, which risk degradation from high-temperature contact fabrication for top cell materials, such as in III-V/Si multijunction cells. This paper presents aluminum (Al) doped and induced poly-Si (formed through annealing at 190 degrees C for 5 min) as localized contacts on p-type silicon absorbers. This approach avoids the high-temperature processes required for poly-Si formation and the toxic gases involved in in-situ doping through chemical vapor deposition. Raman spectroscopy confirms poly-Si formation due to Al-induced recrystallization of a-Si:H(i), with electrochemical capacitance-voltage (ECV) measurements validating Al doping in the newly-formed poly-Si. The contact stack of p-Si/a-Si:H(i)/Al exhibits ohmic behavior after annealing at 190 degrees C for 5 min, achieving a contact resistivity of similar to 13.2 m Omega.cm(2). Finally, a cell featuring a localized Al-doped poly-Si contact structure is fabricated, realizing a 3% absolute efficiency improvement compared to a full-area Al back contact cell.