Myths and reality of HPbI<sub>3</sub> in halide perovskite solar cells.

Ke, Weijun; Spanopoulos, Ioannis; Stoumpos, Constantinos C; Kanatzidis, Mercouri G · Nat Commun · 2018

basic_science · Level V

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Abstract

All-inorganic perovskites have a special place in halide perovskite family because of their potential for better stability. However, the representative cesium lead iodide (CsPbI<sub>3</sub>) is metastable and spontaneously converts to the non-perovskite structure at room temperature. Here, we demonstrate that what appears to be all-inorganic CsPbI<sub>3</sub> stabilized in its perovskite form using the purported intermediate known as hydrogen lead iodide (HPbI<sub>3</sub>) is, in fact, the hybrid perovskite cesium dimethylammonium lead iodide (Cs<sub>1-x</sub>DMA<sub>x</sub>PbI<sub>3</sub>, x = 0.2 to 0.5). Thus, many of the reported all-inorganic perovskites are actually still hybrid organic-inorganic perovskites, as strongly evidenced by a wide battery of experimental techniques presented here. Solar cells based on the representative composition Cs<sub>0.7</sub>DMA<sub>0.3</sub>PbI<sub>3</sub> can achieve an average power conversion efficiency of 9.27 ± 1.28% (max 12.62%). These results provide an alternative angle to look at previous results pertaining all-inorganic CsPbI<sub>3</sub> while the DMA cation is now revealed as an alternative A site cation.