Perovskite solar cells have attracted tremendous attention for their outstanding energy conversion efficiency in the past few years. Due to the development of active materials, device architectures and processing methods, power conversion efficiency (PCE) of perovskite solar cells is now growing up to 20%. Beyond the efficiency, to get rid of Lead, the widely-used toxic element in the perovskite layers, as well as to improve the device/module operation lifetime are the other two major challenges that need to be solved before their commercialization.
Here, we apply a layer of ZnO nanoparticles onto to a planar perovskite solar cell, which can not only improve the electron transport/extraction in the devices but highly improve the device operation lifetime. The devices were fabricated by spin-coating a poly(3,4-ethylenedioxythuiphene):polystyrene sulfonate (PEDOT:PSS) layer onto a glass/ITO substrate, followed by the deposition of a perovskite layer from a lead chloride (PbCl2) and methyl ammonium iodine (MAI) blend precursor solution. After that, a layer of [6,6]-phenyl-C61-butyric acid methyl ester (PCBM) and a layer of ZnO nanoparticles were successively deposited as the electron transport layers, and the device was finished by thermally evaporation Al as the cathode. Such planar perovskite solar cell with ZnO NPs exhibits a maximum PCE of up to 14.1%, which is about 35% higher than that without the ZnO layer. Moreover, the device remains 80% of its initial PCE after 2500 hours under 1 sum illumination, majorly due to the protection of ZnO layer that prevent the diffusion of oxygen and moisture molecules into the perovskite layers as revealed by x-ray photoelectron spectroscopy studies.