Ex situ phosphorus doped polysilicon films by plasma immersion ion implantation (PIII): Controlling and simplifying passivated contacts integration

We report on the relevance of using Plasma Immersion Ion Implantation (PIII) technology for a simple and controlled Phosphorus doping process of polysilicon-based passivated contacts in high efficiency silicon solar cells. Three different ion doses were tested on polysilicon (poly-Si) layers (40 nm thick) / tunnel oxide stacks to study the influence of this parameter on the electron concentration and surface passivation properties. Excellent i-Voc of 732 mV and J0 = 4.1 fA.cm-2 were obtained for hydrogenated poly-Si (n+)/SiO2 structures on polished c-Si substrates after a firing step. For thinner poly-Si films (from 7 nm to 26 nm), only one ion dose was tested resulting in a slight decrease of the passivation levels with the layer thickness. Encouraging values of i-Voc = 700 mV and J0 ∼ 22 fA.cm−2 were also obtained for∼16 nm of poly-Si (n+) on textured c-Si substrates.