Yasuhiro Shirai1 Dhruba Khadka1 Masatoshi Yanagida1 Takeshi Noda1 Chisato Niikura1 Kenjiro Miyano1

1, National Institute for Materials Science, Tsukuba, , Japan

Perovskite PV materials are unique polycrystalline semiconductors that can be deposited on surfaces using low-temperature solution-processes to achieve high efficiencies with high open circuit voltage (Voc) over 1.2 V. The bandgap of the perovskite absorbers can be tuned by controlling the halide (Cl, Br, and I) and cationic (MAI, FAI, Cs, etc.) contents in the crystal. These features make it one of the best materials for the top layer of tandem PV applications. To realize highly efficient and cost effective tandem PV devices, we have developed wide bandgap perovskite cells using low-temperature process (<100°C) as the top cell of perovskite-silicon tandem applications. Here, we developed efficient wide bandgap perovskite based device using highly crystalline fullerene derivatives with long alkyl chains as electron transport layer (ETL). The device with C60-fused N-methylpyrrolidine-meta-dodecyl phenyl (C60MC12) as ETL demonstrated an enhanced efficiency of 16.7 % with VOC of 1.24 V. This was achieved by mitigating the recombination loss through the use of the highly crystalline C60MC12 film compared to amorphous PCBM layer. We also made the entire cell semi-transparent to the bottom c-Si cell by using the ITO electrodes for the top and bottom layers of the perovskite cell. The semi-transparent cells with NiOx hole transport layer achieved over 12% efficiencies, showing no performance degradation over 4000 hours of continuous operation under 1 sun illumination at MPPT. Finally, preliminary studies demonstrated over 16% efficiencies for the perovskite-silicon monolithic two-terminal tandem devices.