Electron transport layer engineering with rubidium chloride alkali halide to boost the performance of perovskite absorber layer

The mesoscopic perovskite solar cells (PSCs) based on titanium oxide (TiO₂) with a certified 25.2% efficiency are the forefront devices in the PSCs field. Hence, it can conclude the mesoporous titanium oxide (mp-TiO₂) is one of the most promising candidates to use as an electron transport layer (ETL) in PSCs. Improving the conductivity of mp-TiO₂ can consider as a simple route to motivate the electron extraction ability of this layer and increase the efficiency of PSCs. Herein, rubidium chloride (RbCl) was introduced as an additive source to boost the optoelectronic properties of mp-TiO₂ ETL. It was observed through ETL modification with RbCl, the optical transmittance of mp-TiO₂ remains constant but increases its electro-conductivity. Results showed that the morphology and crystalline properties of the perovskite layer with a modified ETL substrate is improved. It indicates a perovskite layer with enlarger grains and lower lead iodide (PbI₂) surplus. Altogether, ETL modification brings a champion efficiency of 11.10% for hole transport layer (HTL)-free PSCs higher than that of 8.65% for the HTL-free PSCs based on pristine ETL. Besides, Modified PSCs compared to pristine PSCs showed higher stability response as a result of lower grain boundaries in the modified perovskite layer.