Balancing electrical and optical losses for efficient Si-perovskite 4-terminal solar cells with solution processed percolation electrodes.

The unprecedented efficiency upraise of perovskite-based photovoltaics has sparked the interest in semi-transparent devices, particularly for tandem structures. Despite promising reports regarding efficiency and reduced parasitic absorption, many devices still rely on processes from the gas phase, compromising both applicability and cost factors. Here, we report all-solution perovskite solar cells with improved infrared transparency ideally suited as top-cell for efficient multi-junction device configurations. We demonstrate the functionality of Copper (I) thiocyanate as antireflective layer and selective contact between the transparent conductive oxide and the perovskite as key factor. This concept allows us to fabricate an opaque device with steady state efficiency as high as 20.1%. By employing silver nanowires with robust environmental stability as bottom electrode, we demonstrate different regimes of device performance that can be described through a classical percolation model, leading to semi-transparent solar cells with efficiencies of up to 17.1%. In conjunction with the implementation of an infrared-tuned transparent conductive oxide contact deposited on UV-fused silica, we show a full device average transmittance surpassing 84% between 800 and 1100 nm (as opposed to 77% with PEDOT:PSS as selective contact). Finally, we mechanically staked optimized perovskite devices on top of high performing PERL and IBC silicon architectures. The imputed output efficiency of the 4-terminal measured perovskite-silicon solar cell was 26.7% and 25.2% for PERL-perovskite and IBC-perovskite, respectively.