Stable and Low‐Cost Mesoscopic CH 3 NH 3 PbI 2 Br Perovskite Solar Cells by using a Thin Poly(3‐hexylthiophene) Layer as a Hole Transporter

Mesoscopic perovskite solar cells using stable CH 3 NH 3 PbI 2 Br as a light absorber and low‐cost poly(3‐hexylthiophene) (P3HT) as hole‐transporting layer were fabricated, and a power conversion efficiency of 6.64 % was achieved. The partial substitution of iodine with bromine in the perovskite led to remarkably prolonged charge carrier lifetime. Meanwhile, the replacement of conventional thick spiro‐MeOTAD layer with a thin P3HT layer has significantly reduced the fabrication cost. The solar cells retained their photovoltaic performance well when they were exposed to air without any encapsulation, presenting a favorable stability. The combination of CH 3 NH 3 PbI 2 Br and P3HT may render a practical and cost‐effective solid‐state photovoltaic system. The superior stability of CH 3 NH 3 PbI 2 Br is also promising for other photoconversion applications.