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Binary-Metal Perovskites Toward High-Performance Planar-Heterojunction Hybrid Solar Cells Fan Zuo, Spencer T. Williams, Po-Wei Liang, Chu-Chen Chueh, Chien-Yi Liao, and Alex K.-Y. Jen* Great effort has been made to find promising alternatives for silicon solar cells to drive the widespread implementation of photovoltaic energy production forward.[1–6] Among the innovations in this emerging field, hybrid organolead halide perovskite solar cells have attracted rapidly increasing attention with power conversion efficiencies (PCE) rocketing to 15.7% in less than one year.[7–17] Hybrid organolead perovskites are a class of semiconductors with the chemical formula AMX3 (A = organic molecule, M = Pb, X = Cl, Br, and I).[18–20] Halide anions form a network of corner sharing MX6 octahedra with Pb2+ cations located at the octahedrons’ center. Organic cations occupy the cuboctahedral voids between adjacent octahedra (Figure 1). The great interest in using these hybrid perovskites stems from their unique combination of properties that are critical for high photovoltaic performance: 1) direct band gap with gap size ranging from semiconducting to metallic, tunable through choice of metals,[21,22] halogens,[11] and organic cations;[23] 2) large dielectric coefficient compared to organic polymers leading to small exciton binding energy (∼20 meV),[24] long diffusion lengths (100–1000 nm), and long lifetimes (∼100 ns);[25,26] 3) low temperature (
COMMUNICATION
Binary-Metal Perovskites Toward High-Performance Planar-Heterojunction Hybrid Solar Cells Fan Zuo, Spencer T. Williams, Po-Wei Liang, Chu-Chen Chueh, Chien-Yi Liao, and Alex K.-Y. Jen* Great effort has been made to find promising alternatives for silicon solar cells to drive the widespread implementation of photovoltaic energy production forward.[1–6] Among the innovations in this emerging field, hybrid organolead halide perovskite solar cells have attracted rapidly increasing attention with power conversion efficiencies (PCE) rocketing to 15.7% in less than one year.[7–17] Hybrid organolead perovskites are a class of semiconductors with the chemical formula AMX3 (A = organic molecule, M = Pb, X = Cl, Br, and I).[18–20] Halide anions form a network of corner sharing MX6 octahedra with Pb2+ cations located at the octahedrons’ center. Organic cations occupy the cuboctahedral voids between adjacent octahedra (Figure 1). The great interest in using these hybrid perovskites stems from their unique combination of properties that are critical for high photovoltaic performance: 1) direct band gap with gap size ranging from semiconducting to metallic, tunable through choice of metals,[21,22] halogens,[11] and organic cations;[23] 2) large dielectric coefficient compared to organic polymers leading to small exciton binding energy (∼20 meV),[24] long diffusion lengths (100–1000 nm), and long lifetimes (∼100 ns);[25,26] 3) low temperature (
