Inline Deposited PassDop Layers for Rear Side Passivation and Contacting of p-type c-Si PERL Solar Cells with High Bifaciality

We investigate stacks of aluminum oxide (Al2O3) and boron-doped silicon nitride (SiNX:B) layers for the rear side passivation and local doping of p-type silicon solar cell samples aiming for the realization of bifacial passivated emitter and rear locally diffused (biPERL) solar cells. The local p+-doped back surface field regions are formed by laser doping and are electrically contacted using commercially available screen-printed and fired silver-aluminum (AgAl) or silver (Ag) contacts. This approach is referred to as ""pPassDop"". Laser doping results in highly-doped silicon with sheet resistances as low as 15 O/sq and surface doping concentrations up to 6×1019 cm−3. Low specific contact resistances around 1 mO cm2 and 5 mO cm2 are measured for the screen-printed and fired AgAl and Ag contacts, respectively. In addition, the influence of each individual layer within the pPassDop layer stack on the doping properties is investigated. In order to separate the impact of aluminum and boron doping, firstly the influence of the Al2O3 layer thickness (0 nm, 4 nm, 6 nm) below the SiNX:B capping layer is studied. Secondly, a conventional undoped SiNX capping layer is applied on a 6 nm-thick Al2O3 layer. The roles of each dopant are studied by measuring the doping profile and contact resistivity.