Zn2SnO4-Based Photoelectrodes for Organolead Halide Perovskite Solar Cells

We report a new ternary Zn2SnO4 (ZSO) electron-transporting electrode of a CH3NH3PbI3 perovskite solar cell as an alternative to the conventional TiO2 electrode. The ZSO-based perovskite solar cells have been prepared following a conventional procedure known as a sequential (or two-step) process with ZSO compact/mesoscopic layers instead of the conventional TiO2 counterparts, and their solar cell properties have been investigated as a function of the thickness of either the ZSO compact layer or the ZSO mesoscopic layer. The presence of the ZSO compact layer has a negligible influence on the transmittance of the incident light regardless of its thickness, whereas the thickest compact layer blocks the back electron transfer most efficiently. The open-circuit voltage and fill facor increase with the increasing thickness of the mesoscopic ZSO layer, whereas the short circuit current density decreases with the increasing thickness except for the thinnest one (similar to 100 nm). As a result, the device with a 300 nm-thick mesoscopic ZSO layer shows the highest conversion efficiency of 7%. In addition, time-resolved and frequency-resolved measurements reveal that the ZSO-based perovskite solar cell exhibits faster electron transport (similar to 10 times) and superior charge-collection capability compared to the TiO2-based counterpart with similar thickness and conversion efficiency.