Enhanced Moisture Stability of Perovskite Solar Cells With Mixed‐Dimensional and Mixed‐Compositional Light‐Absorbing Materials

In spite of perovskite solar cells have achieved great progress in recent years, the long term stability of perovskite material is always a big obstacle before commercialization, especially the moisture instability. In this paper, we reported a layered perovskite solar cell based on (CF3CH2NH2)2(FA0.825MA0.15Cs0.025)n−1Pbn(I0.85Br0.15)3n+1 series (n = 1−∞), which possess excellent optoelectronic property and stability. The perovskite film displayed an ultrahigh surface coverage and provided high‐quality thin films which lead to an advancement in solar cells performance. We had fabricated solar cells based on (CF3CH2NH2)2(FA0.825MA0.15Cs0.025)29Pb30(I0.85Br0.15)91 light absorber and got the best PCE of 18.17%. The average PCE of 17.84% was achieved with Jsc of 21.05 mA cm−2, Voc of 1.095V, and FF of 77.4%. Moreover, the multi‐layered perovskite showed excellent property of moisture‐resistant compared to three‐dimensional type PSCs. Under relative humidity level of 65%, the devices without any encapsulation did not deteriorate for up to approximately 28 days with the PCE maintaining over 90%.