The role of rGO sheet and Ag dopant in reducing ZnO electron transport layer recombination in planar perovskite solar cells

Abstract

For planar perovskite solar cells (PSCs) to have satisfactory performance and acceptable stability, an ETL (electron transport layer) is needed that provides a high level of efficiency. It should be noted that when considering the implementation of n-type metal oxide materials, the ZnO (zinc oxide) can be a great choice for an ETL because it provides a relatively high level of mobility. The current study proposes a new design involving a reduced graphene oxide (rGO) sheet/Ag-doped ZnO bilayer to be utilized as ETL in planar PSCs. Extensive experimental and computational analyses including nano-micro structural, optical and electrical properties are carried out in order to compare the performance and governing mechanisms of rGO/Ag-doped bilayer-based planar PSC to ordinary un-doped ZnO. The results from the performed experiments show that using the rGO sheet as the buffer layer and Ag-doped ZnO significantly increase the power conversion efficiency (PCE) by more than 30% compared to un-doped ZnO ETL in planar PSCs. These improvements in the performance of PSCs can be explained based on fine tuning the energy levels of ZnO/perovskite, since this increases the charge-carrier-extraction from the perovskite layer. Moreover, the results of the study confirm the using the rGO/Ag-doped ZnO bilayer ETL as a new methodology for the creation of stable planar PSCs with low charge recombination rate and high performance.