A thin film (<200 nm) perovskite solar cell with 18% efficiency

Abstract

Although the record efficiency of 25.2% was achieved using a 500–1000 nm-thick perovskite film within an appropriate device structure, it is desirable to achieve high efficiency with a thinner perovskite film because the thinner layer can gain benefits of lowering Pb content, reducing cost and better adjustability for a transparent window, flexible device and tandem structure. Here, we report on a high efficiency thin film (<200 nm) perovskite solar cell. An ∼170 nm-thick ethylammonium lead iodide (EAPbI₃) film is stamped with a methylammonium (MA)-reservoir MAPbI₃ film. A facilitated cation transport during stamping results in a phase conversion from orthorhombic EAPbI₃ to cubic MAPbI₃, along with an enlarged grain size. ¹H NMR study reveals that the stamped EAPbI₃ film is composed of MAPbI₃ which is self-passivated with EA. A device with the stamped ∼170 nm-thick EAPbI₃ delivers a power conversion efficiency of 18.0%, together with long-term stability maintaining 98% of the initial PCE after storing the device for 36 days in the ambient atmosphere. It is also discovered that the photovoltaic performance of the stamped ∼170 nm-thick EAPbI₃ is superior to that of the conventional spin-coated MAPbI₃ with a similar film thickness (∼200 nm) due to a higher absorption coefficient and longer carrier lifetime.