Viscosity effect of ionic liquid-assisted controlled growth of CH3NH3PbI3 nanoparticle-based planar perovskite solar cells

A precise control of the morphology and crystallization of perovskite thin-films is well-correlated to higher perovskite solar cells performances. Ionic liquids (ILs) can retard perovskite crystallization to aid the formation of films with uniform morphology to realize highly efficient perovskite solar cells. Herein, we attempt to control the nanostructural growth of CH3NH3PbI3 thin films by adding ILs to the perovskite spin-coating solution and investigate the effect of IL viscosity on the resulting CH3NH3PbI3 nanoparticle (NP) thin films. NPs with desirable morphology were obtained using ILs with a low viscosity that completely dissolved in the CH3NH3PbI3 solution. In particular, the IL tetrabutylammonium chloride yielded NPs with a diameter of 500 nm and controllable morphology, crystallinity, and absorption behavior, which led to improved photovoltaic performance compared with that of solar cells containing NPs produced using other ILs. Our findings revealed a pathway to obtain uniformly distributed CH3NH3PbI3 NP thin films for use in perovskite solar cells. The developed method is well suited for largescale production of perovskite thin films on flexible substrates. (C) 2017 Elsevier B.V. All rights reserved.