Record Open-Circuit Voltage in Perovskite/PERC Tandem Solar Cells via Novel a-Si Interlayer Passivation

Monolithic perovskite/silicon tandem (PST) solar cells are rapidly emerging as next-generation solar cells with significant potential for commercialization. This study presents a proof of concept for a silicon diffused junction-based PST cell, utilizing a passivated emitter rear contact (PERC) cell with a low-temperature (<200 °C) laser-fired contact process to minimize thermal damage. By introducing amorphous silicon to the emitter surface of PERC bottom cell, the open circuit voltage (V_oc) improve from 0.58 V to 0.61 V due to the passivation effect, which reduces silicon surface recombination. Perovskite is passivated using ammonium salts with varying alkyl chain lengths, including n-Butylammonium bromide, n-Hexylammonium bromide, and n-Octylammonium bromide (OABr). OABr is the most effective, increasing the V_oc of the perovskite top cell from 1.18 V to 1.22 V by reducing non-radiative recombination. The best-performing PST cell achieves a power conversion efficiency (PCE) of 25.71%, with a current density of 17.62 mA cm^{- 2}, V_oc of 1.810 V, and fill factor of 80.62%. This represents the highest V_oc and PCE reported for PST cells with PERC-based p-type silicon bottom cell technology. Even after 1000 hours of damp heat testing at 85 °C and 85% relative humidity, the device with dual passivation maintained 90.70% of its initial PCE.