The application of molybdenum oxide (MoOx) as a hole-selective contact for silicon-based solar cells has been explored due to superior optical transmittance and potentially leaner manufacturing compared to fully amorphous silicon-based heterojunction (SHJ) devices. However, the development of MoOx contacts has been hampered by their poor thermal stability, resulting in a carrier selectivity loss and an S-shaped IV curve. The aim of this study is to understand the influence of different passivating interlayers on the carrier selectivity of hole-selective MoOx contacts for crystalline silicon (c-Si) solar cells. We highlight the effect of different interlayers on the surface passivation quality, contact selectivity, and the thermal stability of our MoOx-contacted devices. The interlayers studied are intrinsic hydrogenated amorphous silicon (a-Si:H(i)), thermally grown ultrathin SiO2, and a stack consisting of an ultrathin SiOy and Al2O3 layer. Additionally, we simulate the interacting interlayer properties on the carrier selectivity of our MoOx contacts using a simplified model. Among these interlayers, the Al2O3/SiOy stack shows to be a promising alternative to SiO2 by enabling efficient transport of holes while being able to sustain an annealing temperature of at least 250 °C underlining its potential in module manufacturing and outdoor operation.

In this work, the applicability of pulsed laser deposition (PLD) of transparent conductive oxides (TCOs) on high-quality ultra-thin poly-Si based passivating contacts is explored. Parasitic absorption caused by poly-Si layers can be minimized by reducing the poly-Si layer thickness. However, TCO deposition on poly-Si contacts, commonly by sputtering, results in severe deposition-induced damage and further aggravates the surface passivation for thinner poly-Si layers (<20 nm). Although a thermal treatment at elevated temperature (∼350 °C) can be used to partially repair the surface passivation quality, the contact resistivity severely increases due to the formation of a parasitic oxide layer at the poly-Si/ITO interface. Alternatively, we show that PLD TCOs can be used to mitigate the damage on ultra-thin (∼10 nm) poly-Si layers. Further improvement in poly-Si contact passivation can be achieved by increasing the deposition pressure while low contact resistivities (∼45 mΩ cm²) and good thermal stability (up to 350 °C) are achieved with a PLD indium-doped tin oxide (ITO) layer on high-quality ultra-thin poly-Si(n⁺) contacts. This allows for the application of a highly transparent front side contact by combining the excellent opto-electrical properties of a PLD ITO film with a 10 nm thin poly-Si contact.