Heated ITO depositions onto poly-Si passivated contacts enabling efficient 16-cm2 perovskite/silicon tandem solar cells

The use of double-sided (DS) thin polysilicon (poly-Si) layers for tunnel oxide passivated contacts (TOPCon) is a promising technology for Si bottom cells in perovskite/silicon tandem (PST) solar cells. DS-TOPCon bottom cells can provide excellent surface passivation, low parasitic absorption, potentially lower cost than other Si bottom cells, and industrial compatibility. Nevertheless, their limited lateral conductivity at reduced poly-Si thickness necessitates the deposition of an additional conductive layer when forming the device contacts, often in the form of a transparent conductive oxide (TCO) by sputtering. Additionally, a TCO also serves as an effective interconnection layer with the perovskite top cell in a PST. However, sputtering is known to induce damage to the passivation quality provided by the DS-TOPCon structure. In this work, we propose a novel process of heated indium tin oxide (ITO) depositions to minimise the sputtering damage and enable high efficiencies on large-area PST solar cells. We investigate (i) the impact of high-temperature depositions on the ITO properties, (ii) the effects of in-situ annealing in the heated sputtering chamber, and (iii) the use of bilayers to limit the sputtering damage. The optoelectronic characterisation of the ITO layers reveals that the high-temperature depositions improve transparency and carrier mobility of the TCO films without severely affecting the passivation properties of the poly-Si layers. M2-sized (244 cm 2 ) full-wafer DS-TOPCon bottom cells with 1-Sun efficiencies of up to 16.7% are used to fabricate proof-of-concept, fully screen-printed 16-cm 2 planar PST solar cells reaching 22.1%.