Metal-Free Interconnecting Layer for Monolithic Perovskite/Organic Tandem Solar Cells with Enhanced Outdoor Stability

Photovoltaics with monolithically connected tandem architectures have the potential to achieve high efficiencies owing to enhanced spectral absorption and reduced thermal losses. To achieve this, photoactive layers with complementary absorption and interconnecting layers, which are robust, transparent, and energetically suitable, are essential. Here, we investigate a strategy to create an efficient, highly transparent, ohmic, and chemically robust interconnecting layer based on atomic layer-deposited tin oxide (SnO2) and solution-processed diluted poly(3,4-ethylenedioxythiophene):polystyrene sulfonate (PEDOT:PSS), eliminating the need of widely reported parasitically absorbing metal recombination layers. Monolithic perovskite/organic tandem devices built on a metal-free interface (SnO2/PEDOT:PSS) compared to its counterpart (SnO2/metal/PEDOT:PSS) show no significant difference in PCE, but a remarkable enhancement in photostability. Furthermore, tandem solar cells were tested under outdoor conditions for 2 weeks, showing improved stability and solar power conversion than single-junction perovskite and organic devices, underscoring the potential of monolithic tandem solar cells.