Mesoporous BaTiO₃/TiO₂ Double Layer for Electron Transport in Perovskite Solar Cells

We report on the effect of BaTiO₃/TiO₂ mesoporous double layer (MDL) in the electron transport layer (ETL) of perovskite solar cells and enhancement of the photovoltaic performance. The conversion efficiency was enhanced from 9.89% for TiO₂ mesoporous single layer (MSL) to 12.4% for BaTiO₃/TiO₂ MDL. The CH₃NH₃PbI₃ crystal size on the BaTiO₃/TiO₂ MDL was larger. The larger CH₃NH₃PbI₃ crystals resulted in the better light absorption and improved <i>J</i>_SC. Moreover, <i>V</i>_OC was also improved by suppressing a charge recombination, which is attributable to the fewer CH₃NH₃PbI₃ crystal boundaries and band structure of BaTiO₃/TiO₂ MDL. The results suggest that using BaTiO₃ as the second layer of the TiO₂ mesoporous layer is a promising way to boost the performance of perovskite solar cells

Mesoporous BaTiO₃/TiO₂ Double Layer for Electron Transport in Perovskite Solar Cells

We report on the effect of BaTiO₃/TiO₂ mesoporous double layer (MDL) in the electron transport layer (ETL) of perovskite solar cells and enhancement of the photovoltaic performance. The conversion efficiency was enhanced from 9.89% for TiO₂ mesoporous single layer (MSL) to 12.4% for BaTiO₃/TiO₂ MDL. The CH₃NH₃PbI₃ crystal size on the BaTiO₃/TiO₂ MDL was larger. The larger CH₃NH₃PbI₃ crystals resulted in the better light absorption and improved <i>J</i>_SC. Moreover, <i>V</i>_OC was also improved by suppressing a charge recombination, which is attributable to the fewer CH₃NH₃PbI₃ crystal boundaries and band structure of BaTiO₃/TiO₂ MDL. The results suggest that using BaTiO₃ as the second layer of the TiO₂ mesoporous layer is a promising way to boost the performance of perovskite solar cells

Perovskite Solar Cells Prepared by Advanced Three-Step Method Using Additional HC(NH₂)₂I Spin-Coating: Efficiency Improvement with Multiple Bandgap Structure

In the conventional two-step prepared perovskite solar cells, the CH₃NH₃PbI₃ (MAPbI₃) film usually contains an unreacted PbI₂ at the interface between an electron transport layer (ETL) and a perovskite active layer. To reduce the unreacted PbI₂ in the two-step prepared MAPbI₃ film, we have recently reported a new three-step method, which was realized by an additional MA­(I,Br) spin-coating. Here, we propose an advanced three-step method, viz., an additional HC­(NH₂)₂I (FAI) spin-coating on the two-step prepared MAPbI₃ film. The additional FAI spin-coating formed a FA_<i>x</i>MA_1–<i>x</i>PbI₃ solid solution by the incorporation of FA ion into MAPbI₃. Also, the additional FAI spin-coating yielded a FA_<i>y</i>MA_1–<i>y</i>PbI₃ layer (<i>y</i> > <i>x</i>) by converting the unreacted PbI₂, which resulted in the layered structure with different FA concentrations and hence, with the multiple bandgap structure. The best PCE of 18.1% was achieved by optimizing the FAI spin-coating process