Efficiency improvement of perovskite solar cells by charge transport balancing using length tunable ZnO nanorods and optimized perovskite morphology

Well-aligned ZnO nanorods with tunable length are successfully deposited using a low-temperature chemical bath deposition method, and subsequently used in constructing solar cells with the structure of FTO/ZnO nanorods/MAPbI(3-x)Cl(x)/P3HT/Au. The charge transport is balanced by tuning the length of nanorods and improving the morphology of the perovskite layer. Uniformity and charge transport within the film is improved by doping the perovskite structure with Cl- ions. The photovoltaic characteristics of the cells are improved as the length of nanorods increases from 300 nm to 460 nm, and deteriorate as it increases further. Using nanorods with the length of 460 nm, power conversion efficiency of 12.85% and J(sc) over 22 mA/cm(2) are obtained. This efficiency is in the range of the best efficiencies reported so far using P3HT as the hole transporting layer (HTL) and ZnO as the electron transporting layer (ETL). For the first time, PSCs based on ZnO nanorods are fabricated, in which copper iodide is deposited as the inorganic HTL through vapor iodination of Cu film. A promising efficiency of 8.09% is achived which is in the range of the highest efficiencies reported for n-i-p PSCs with CuI as the HTL.

Automated summary

In this study, well-aligned ZnO nanorods with tunable length were successfully deposited and utilized in solar cells, balancing charge transport by adjusting the nanorod length and improving the morphology of the perovskite layer. The photovoltaic characteristics of the cells improved with increasing nanorod length up to 460 nm, but deteriorated further. Doping the perovskite structure with Cl- ions improved film uniformity and charge transport.