LAUSR

Tandem solar cells (SCs) based on perovskite and silicon represent an exciting possibility for a breakthrough in photovoltaics, enhancing solar cell power conversion efficiency (PCE) beyond the single junction limit while keeping the production cost low. A critical aspect to push the tandem PCE close to their theoretical limit is the development of high-performing semi-transparent perovskite top-cells which also allow suitable near-infrared transmission. Here, we have developed highly efficient semi-transparent perovskite solar cells (PSCs) based on both mesoporous and planar architectures, employing Cs0.05(MA0.17FA0.83)0.95Pb(I0.83Br0.17)3 and FA0.87Cs0.13PbI2Br perovskites with bandgap of 1.58eV and 1.72eV respectively which achieved PCEs well above 17% and 14% by detailed control of the deposition methods, thickness and optical transparency of the interlayers and the semi-transparent electrode. By combining our champion 1.58eV PSCs (PCE of 17.7%) with an industrial-relevant low-cost n-type Si SCs, a 4 terminals (4T) tandem efficiency of 25.5% has been achieved. Moreover, for the first time, 4T tandem SCs performances have been measured in the low light intensity regime achieving a PCE of 26.6%, corresponding to a revealing a relative improvement above 9 % compared to standard 1 sun illumination condition. These results are very promising for their implementations under field-operating conditions.