Sequentially Deposited Antimony-Doped CH₃NH₃PbI₃ Films in Inverted Planar Heterojunction Solar Cells with a High Open-Circuit Voltage

We introduce antimony-doped hybrid perovskite compounds in planar inverted solar cells. Here, we report in-depth and systematic studies on the formation of the perovskite layer through a modified two-step spin-coat method. In this method, the “loading time” of CH₃NH₃I on a “wet” PbI₂ layer was varied in achieving a complete conversion to the perovskite material. The “loading time” that in turn also controlled morphology of the perovskite layer along with the antimony content in perovskite compounds was varied to optimize the solar cell performances. The effect of dopant content has affected the band diagram, which was drawn from density of states of the components as derived from their scanning tunneling spectroscopy. The solar cell parameters were then correlated with the experimental band diagram of the heterojunctions. In Cu@NiO|CH₃NH₃Pb_0.92Sb_0.08I₃|PCBM p–i–n heterojunctions, we have achieved a high open-circuit voltage of 1.13 V with an energy conversion efficiency of 12.8%. The solar cell parameters have been correlated with junction properties, which have been studied through in-depth analysis of diode characteristics