*2.1. Materials*

Poly(3,4-ethylenedioxythiophene) polystyrene sulfonate (PEDOT:PSS, P AI 4083) was bought from Heraeus Co. (Hanau, Germany). 6,6-phenyl C61-butyric acid methyl ester (PCBM) was purchased from Nano-C Inc. (Westwood, MA, USA). 2,9-dimethyl-4,7- diphenyl-1,10-phenanthroline (BCP) was obtained from Xi'an Polymer Light Technology Corp (Xi'an, China). CsI was purchased from Sigma Aldrich (St. Louis, MO, USA). Methylammonium Iodide (MAI) was provided by Great Cell Solar (Queanbeyan, Australia). Pb(Ac)2 was provided by Tokyo Chemical Industry (Tokyo, Japan).
