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Band Gap Tuning via Lattice Contraction and Octahedral Tilting in Perovskite Materials for Photovoltaics
Journal of the American Chemical Society ( IF 14.4 ) Pub Date : 2017-08-04 00:00:00 , DOI: 10.1021/jacs.7b04981 Rohit Prasanna 1 , Aryeh Gold-Parker 2, 3 , Tomas Leijtens 1 , Bert Conings 4 , Aslihan Babayigit 4 , Hans-Gerd Boyen 4 , Michael F. Toney 3 , Michael D. McGehee 1
Journal of the American Chemical Society ( IF 14.4 ) Pub Date : 2017-08-04 00:00:00 , DOI: 10.1021/jacs.7b04981 Rohit Prasanna 1 , Aryeh Gold-Parker 2, 3 , Tomas Leijtens 1 , Bert Conings 4 , Aslihan Babayigit 4 , Hans-Gerd Boyen 4 , Michael F. Toney 3 , Michael D. McGehee 1
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Tin and lead iodide perovskite semiconductors of the composition AMX3, where M is a metal and X is a halide, are leading candidates for high efficiency low cost tandem photovoltaics, in part because they have band gaps that can be tuned over a wide range by compositional substitution. We experimentally identify two competing mechanisms through which the A-site cation influences the band gap of 3D metal halide perovskites. Using a smaller A-site cation can distort the perovskite lattice in two distinct ways: by tilting the MX6 octahedra or by simply contracting the lattice isotropically. The former effect tends to raise the band gap, while the latter tends to decrease it. Lead iodide perovskites show an increase in band gap upon partial substitution of the larger formamidinium with the smaller cesium, due to octahedral tilting. Perovskites based on tin, which is slightly smaller than lead, show the opposite trend: they show no octahedral tilting upon Cs-substitution but only a contraction of the lattice, leading to progressive reduction of the band gap. We outline a strategy to systematically tune the band gap and valence and conduction band positions of metal halide perovskites through control of the cation composition. Using this strategy, we demonstrate solar cells that harvest light in the infrared up to 1040 nm, reaching a stabilized power conversion efficiency of 17.8%, showing promise for improvements of the bottom cell of all-perovskite tandem solar cells. The mechanisms of cation-based band gap tuning we describe are broadly applicable to 3D metal halide perovskites and will be useful in further development of perovskite semiconductors for optoelectronic applications.
中文翻译：
钙钛矿材料中通过晶格收缩和八面体倾斜的带隙调谐
成分为AMX 3的锡和碘化钙钛矿型半导体（其中M为金属，X为卤化物）是高效低成本串联光伏电池的主要候选产品，部分原因是它们的带隙可以在很宽的范围内调节成分替代。我们通过实验确定了两种竞争机制，通过这些机制，A位阳离子会影响3D金属卤化物钙钛矿的带隙。使用较小的A-位阳离子可以两种不同的方式扭曲钙钛矿晶格：倾斜MX 6八面体或仅通过各向同性收缩晶格即可。前者趋于增大带隙，而后者趋于减小带隙。由于八面体倾斜，碘化铅钙钛矿显示出较大的甲ami部分取代了较小的铯后，带隙增加。相反的趋势是，基于锡的钙钛矿（略小于铅）显示出相反的趋势：它们在Cs取代时没有八面体倾斜，而只有晶格收缩，从而导致带隙逐渐减小。我们概述了通过控制阳离子组成来系统地调节金属卤化物钙钛矿的带隙，价和导带位置的策略。使用这种策略，我们演示了太阳能电池可收集高达1040 nm的红外光，达到了17.8％的稳定功率转换效率，显示出有望改善全钙钛矿串联太阳能电池底部电池的前景。我们描述的基于阳离子的带隙调节机理广泛适用于3D金属卤化物钙钛矿，并将在进一步开发用于光电应用的钙钛矿半导体中有用。
更新日期：2017-08-04
中文翻译：
钙钛矿材料中通过晶格收缩和八面体倾斜的带隙调谐
成分为AMX 3的锡和碘化钙钛矿型半导体（其中M为金属，X为卤化物）是高效低成本串联光伏电池的主要候选产品，部分原因是它们的带隙可以在很宽的范围内调节成分替代。我们通过实验确定了两种竞争机制，通过这些机制，A位阳离子会影响3D金属卤化物钙钛矿的带隙。使用较小的A-位阳离子可以两种不同的方式扭曲钙钛矿晶格：倾斜MX 6八面体或仅通过各向同性收缩晶格即可。前者趋于增大带隙，而后者趋于减小带隙。由于八面体倾斜，碘化铅钙钛矿显示出较大的甲ami部分取代了较小的铯后，带隙增加。相反的趋势是，基于锡的钙钛矿（略小于铅）显示出相反的趋势：它们在Cs取代时没有八面体倾斜，而只有晶格收缩，从而导致带隙逐渐减小。我们概述了通过控制阳离子组成来系统地调节金属卤化物钙钛矿的带隙，价和导带位置的策略。使用这种策略，我们演示了太阳能电池可收集高达1040 nm的红外光，达到了17.8％的稳定功率转换效率，显示出有望改善全钙钛矿串联太阳能电池底部电池的前景。我们描述的基于阳离子的带隙调节机理广泛适用于3D金属卤化物钙钛矿，并将在进一步开发用于光电应用的钙钛矿半导体中有用。
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