Solvent selection for fabrication of low temperature ZnO electron transport layer in perovskite solar cells

Abstract Zinc Oxide ( Z n O ) with an easy synthesis method, low processing temperature, and high charge carrier mobility has been considered as a proper electron transport layer ( E T L ) for perovskite solar cells. Herein, we investigate the effect of the most common solvents for the preparation of Z n O and investigate their application as E T L for PSC. Z n O layers were prepared from three different solvents 2-methoxyethanol ( 2 M E ) , isopropyl alcohol ( I P A ) and e t h a n o l . A complete investigation of the structural, morphological, optical and device performance was performed. The results show that the type of solvent has a significant effect on electrical, optical and structural properties of Z n O layer, the capping perovskite layer composed of methyl ammonium lead iodide ( M A P b I 3 ) and the total performance of the cell. The Z n O film prepared by 2 M E as the solvent showed the best performance mainly because of better surface coverage by M A P b I 3 , larger grain sizes, fewer pinholes, satisfying the P b / I theoretical stoichiometry in the perovskite layer and the highest absorbance compared to other solvents. In addition, the simulation modeling shows that the Z n O ( 2 M E ) / M A P b I 3 interface has the lowest defect density and for having planar Z n O -based PSCs with PCE of over 22%, the interface defects should be kept under 10 13 c m − 3 .