Simple silicon solar cells featuring an a-Si:H enhanced rear MIS contact

• MIS contacts with an a-Si:H(i) capping layer are trialled on silicon solar cells.
• The impact of SiOx thickness and thermal budget is investigated.
• Optimum conditions: SiOx thickness of 1.6 nm and ∼30 min annealing at 425 °C.
• Champion cell achieves 21.0% with a Voc of 666 mV and a FF of 0.805.

This paper presents the experimental demonstration of silicon solar cells that incorporate an enhanced MIS passivated contact scheme on a phosphorus diffused surface. By depositing intrinsic a-Si:H on an ultrathin SiOx layer and alloying with an overlying aluminium layer, the interface passivation has been vastly improved over that of conventional MIS contacts, whilst maintaining a low contact resistance. This paper focuses on the optimisation of the Al/a-Si:H alloying process and the influence of the tunnelling SiOx layer thickness. A conversion efficiency of 21.0% has been achieved for n-type cells fabricated with a front boron diffusion and a full area rear MIS passivated phosphorus diffusion. The cells exhibit a moderate Voc=666 mV and FF=0.805, whereas Jsc 39.3 mA/cm2 is relatively low due to a non-optimal antireflection coating and back surface reflector, and hence will be subject to further improvement.