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

Zinc Oxide (ZnO) with an easy synthesis method, low processing temperature, and high charge carrier mobility has been considered as a proper electron transport layer (ETL) for perovskite solar cells. Herein, we investigate the effect of the most common solvents for the preparation of ZnO and investigate their application as ETL for PSC. ZnO layers were prepared from three different solvents 2-methoxyethanol (2ME), isopropyl alcohol (IPA) and ethanol. 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 ZnO layer, the capping perovskite layer composed of methyl ammonium lead iodide (MAPbI3) and the total performance of the cell. The ZnO film prepared by 2ME as the solvent showed the best performance mainly because of better surface coverage by MAPbI3, larger grain sizes, fewer pinholes, satisfying the Pb/I theoretical stoichiometry in the perovskite layer and the highest absorbance compared to other solvents. In addition, the simulation modeling shows that the ZnO (2ME)/MAPbI3 interface has the lowest defect density and for having planar ZnO-based PSCs with PCE of over 22%, the interface defects should be kept under 10(13) cm(-3)

Phenomenological morphology design of hybrid organic-inorganic perovskite solar cell for high efficiency and less hysteresis

In this report, a modeling approach is employed to study the effect of the grain boundaries (GBs) and their electronic activity on the performance parameters of the perovskite solar cells (PSCs). Our model is based on the 1- dimensional drift-diffusion framework to engage the electron (hole) defects formed in the GBs and the GB's location through the perovskite layer. Power conversion efficiency (PCE) of the PSC is optimized with regards to the perovskite layer thickness, GBs location and perovskite layer band offset with GBs layer. The results shows that the location or the distribution of the GBs can vary the PCE of PSCs from 12% to around 21%, thereby making proper morphology engineering and passivation of GBs is a chief requirement for achieving high efficiency. PCEs larger than 21% require GB defect densities below 10(15) cm(-2). It is demonstrated that the band offset of about 100 meV with GB width of 1 nm could effectively suppress the negative impact of the GBs throughout the entire perovskite layer. Interestingly, GBs location at closer points to electron transport layer (ETL)/perovskite interface may give rise to higher PCEs, however, relatively stronger hysteresis in current values is observed. The results here provide insight into the effect of the GBs location and their corresponding type of defects on the hysteresis and the PSC performance and opens up new horizons to find solutions for current PSC's shortcomings