N-type polysilicon passivating contact combined with hydrogen-containing TCO as the interconnected structure for perovskite/silicon tandem solar cells

An interconnected structure of perovskite/silicon tandem solar cell is the key point to accomplishing high efficiency over 30% due to its high performance of carrier recombination and tunneling. In general, an interconnected structure is designed by a polysilicon (poly-Si) passivating contact structure and a hydrogen-containing transparent conductive oxides (TCO). When the bottom cell structure was fabricated in mass production, poly-Si passivating contact inevitably suffered from a degradation of the passivation quality associated with the metallization firing process. In this work, we investigated the effect of hydrogen-containing indium tin oxide (ITO:H) and Al-doped ZnO (AZO:H) prepared by dc magnetron sputtering on poly-Si passivating contacts passivation degradation. The passivation quality of the poly-Si passivating contacts can be significantly improved by sputtering and annealing at 350 °C after firing of both the hydrogen-containing TCOs. The improvement on poly-Si passivating contacts passivation quality increased with the increased of annealing dwell time. When at the optimal annealing time of 30 min, the iVoc value of ITO:H increased to 725 mV while that of AZO:H increased to 710 mV, respectively. In addition, the optical and electrical properties of ITO films can be improved by annealing process, including transmittance, optical bandgap, Hall mobility and resistivity. When the annealing time is less than 30min, the contact resistivity between Ag/ITO and doped poly-Si increases slightly with the increase of annealing time. However, the optical and electrical properties of AZO films degraded, which may be due to the instability of the prepared AZO:H films. Eventually, based on this interconnected structure, a perovskite/Si tandem cell structure was designed, and silicon substrate cells could be fabricated in mass production.