Ambient Fabrication of 126 μm Thick Complete Perovskite Photovoltaic Device for High Flexibility and Performance

To reap the benefit of low-cost and high-efficiency perovskite photovoltaic devices is to establish a continuous ambient fabrication of device by rapid solution coating without energy- and time-consuming processes such as dry oxygen-free atmosphere and high temperature treatments. Today, an increasing number of wireless devices in consumer electronics and the Internet of Things is creating a large demand for lightweight power sources. Implementation of a plastic film or tape as an extremely lightweight photovoltaic device extends versatile applications of the film device if high mechanical stability is guaranteed. Here, we report a continuous ambient and low-temperature method to fabricate a thin film photovoltaic device comprising a triple cation perovskite absorber Cs0.05(FA0.83MA0.17)0.95Pb(I0.83Br0.17)3 and a mesoporous TiO2 scaffold. An extremely light 126 μm thick photovoltaic device was fabricated under the ambient humidity of 15–25%. With the best power conversion efficiency of 18%, the flexible device showed mechanical stability against more than 1,000 times bending (radius as low as 5 mm), retaining 90% of its initial efficiency. We found that introduction of a short preheating process on the TiO2-coated plastic film before perovskite crystallization effectively reduced thermal expansion stress leading to large grain growth and high coverage of the perovskite absorber.