Development of Inkjet-Printed Doping for Poly-Si Passivating Contacts in Silicon Solar Cells

We present inkjet printing using phosphorous as the dopant species for the fabrication of high-quality  localized polycrystalline silicon (poly-Si) passivating contacts. A detailed study on the impacts of inkjet printer settings, dopant source concentration and annealing temperature on the poly-Si passivating contacts performance was carried out. By applying the optimized process conditions on symmetrical industrially processed intrinsic polycrystalline silicon (i-poly-Si) / SiOx / n-type crystalline silicon (c-Si) / SiOx / i-poly-Si substrates, good surface passivation was achieved, reaching directly after annealing at 975 °C an implied open-circuit voltage (iVoc) of 699 mV together with a contact resistivity of 6.4 mΩ⋅cm2. After hydrogenation via the deposition of an aluminium oxide (AlOx) / silicon nitride (SiNx) stack and subsequent forming gas annealing, the optimum annealing temperature shifted to 950 °C and the iVoc further improved to an outstanding value of 729 mV. Optical microscopy and microphotoluminescence show that a minimum line width of about 50 µm can be achieved after process optimization. Owing to its features of high flexibility, accuracy, safety, low fabrication cost and wide tolerance to chemicals, inkjet printing is a promising technology that can enable the simple fabrication of advanced poly-Si solar cell structures, such as Interdigitated Back Contact (IBC) cells.