Properties of double electron transport layered perovskite solar cells with different ZrO₂ layer thickness

The photovoltaic properties of TiO₂/ZrO₂ double electron transport layered perovskite solar cells were investigated based on the ZrO₂ layer thickness. Samples were fabricated with a glass/FTO/TiO₂/ZrO₂/ perovskite structure. The TiO₂/ZrO₂ layer thickness ratio was confirmed to be 264/0, 228/168, 228/204, 270/ 242, and 282/288 nm, respectively, using an electron probe microanalyzer. To analyze the photovoltaic characteristics and transmittance of the ZrO₂ layer of the PSCs according to the ZrO₂ layer thickness, a solar simulator, incident photon-to-current conversion efficiency, and ultraviolet-visible-near-infrared spectroscopy were used, respectively. A field emission scanning electron microscopy and atomic force microscopy were used to analyze the microstructure of the ZrO₂ and perovskite layers. As the ZrO₂ layer thickness increased, the energy conversion efficiency (ECE) increased initially, reached a maximum ECE of 14.24% at 204 nm ZrO₂, and then decreased thereafter. The increase in ECE was due to the enhanced electrical conductivity of the ZrO₂, while the decrease was attributed to the reduced transmittance as the thickness of the ZrO₂ increased. In addition, we confirmed that the surface valley spacing in the ZrO₂ layer might affect the grain size and thickness of the perovskite layers, influencing the ECE.