Large Grain Growth and Energy Alignment Optimization by Diethylammonium Iodide Substitution at A Site in Lead-Free Tin Halide Perovskite Solar Cells

摘要

Environment-friendly tin perovskite solar cells (T-PKSCs) are the most suitablealternative candidate for lead-free PKSCs. However, the photovoltaic performanceof such T-PKSCs is far below those of lead-based perovskite solar cells dueto an energetic mismatch between the perovskite layer and charge transportlayers. Herein, it is shown that, by partial substitution of the A-site cation usingdiethylammonium iodide (DEAI) substitution, deeper energy levels are obtained.At the same time, the trap density is reduced and the grain size is significantlyimproved. The fabricated solar cell shows much enhanced efficiency from 7.31%to 10.28%, short-circuit current density from 18.68 to 21.69 mA cm~(-2), opencircuitvoltage from 0.59 to 0.67 V, and fill factor from 0.67 to 0.71 after DEAIsubstitution. Such an efficiency improvement can be explained by matchingenergy levels at the interfaces between perovskite layer and the charge transportlayers. In addition, after 50 days of storage, the modified T-PKSCs demonstratehigh stability maintaining 78% of its initial efficiency, whereas the referencedevice degrades to 68% during 28 days storage.