Two-terminal Perovskite silicon tandem solar cells with a high-Bandgap Perovskite absorber enabling voltages over 1.8 V

Perovskite silicon tandem solar cells are a promising technology to overcome the efficiency limit of silicon solar cells. Although highest tandem efficiencies have been reported for the inverted p-i-n structure, high-efficiency single junction perovskite solar cells are mostly fabricated in the regular n-i-p architecture. In this work, regular n-i-p perovskite solar cells with a high-bandgap mixed cation mixed halide absorber suitable for tandem solar cells are investigated by compositional engineering and the open-circuit voltage is improved to over 1.12 V using a passivating electron contact. The optimized perovskite solar cell is used as a top cell in a monolithic perovskite silicon tandem device with a silicon heterojunction bottom cell allowing for voltages up to 0.725 V. The tandem solar cells with an active area of 0.25 cm(2) achieve record open-circuit voltages of up to 1.85 V and have efficiencies over 20%. Analyzing the perovskite absorber by spatially resolved photoluminescence measurements shows a homogenous and stable emission at similar to 1.7 eV which is an optimal value for tandem applications with silicon. The tandem solar cells are mainly limited due to a low current. A spectrometric characterization reveals that the perovskite solar cell is current limiting which could be improved by a thicker perovskite absorber.