Bismuth Telluride Interlayer for All-Inorganic Perovskite Solar Cells with Enhanced Efficiency and Stability

To solve the thermal instability issue of organic–inorganic hybrid perovskites, all-inorganic perovskite solar cells (PSCs) have been featured in the spotlight. However, their power conversion efficiencies (PCEs) are far from satisfactory due to the substantially radiative and nonradiative recombination of charge carriers in the common-structured devices. Herein, bismuth telluride (Bi 2 Te 3 ) nanoplates are designed as an interlayer between cesium lead halide (CsPbBrI 2 ) and 2,2′,7,7′-tetrakis( N , N -di-p-methoxyphenylamine)-9,90-spirobifluorene (Spiro-OMeTAD) to reduce the notorious trap states and charge recombination. Confirmed by systematic electrochemical and photoelectrical techniques, the Bi 2 Te 3 interlayer optimizes hole extraction and transport efficiency because of the matched band level structure and drastically reduces trap defect densities. Prolonged effective lifetime and shorter diffusion time induced by the Bi 2 Te 3 interlayer reveal less electron–hole recombination and more efficient carrier transport, which lead to a larger photocurrent and less open circuit voltage loss of PSCs. The all-inorganic PSCs with the optimal Bi 2 Te 3 interlayer exhibit a highly enhanced PCE of 11.96%. Moreover, Bi 2 Te 3 also acts as a blocking layer for the migration of iodide ions, silver, and moisture, resulting in a considerable device stability of more than 70% of initial PCE after 50 days without extra encapsulation. This low-cost and facile method for efficient and stable all-inorganic PSCs offers great promise as a next-generation renewable energy source.