Mixing iodide and bromide in halide perovskite semiconductors is an effective strategy to tune their band gap; therefore, mixed-halide perovskites hold great promise for color-tunable LEDs and tandem solar cells. However, the band gap of mixed-halide perovskites is unstable under (sun-)light, since the halides segregate into domains of different band gaps. Using pressure-dependent ultrafast transient absorption spectroscopy, we find that high external pressure increases the range of stable halide mixing ratios. Chemical compression, by inserting a smaller cation, has the same effect, which means that any iodide:bromide ratio can be stabilized by tuning the crystal volume and compressibility. We interpret these findings as an increased thermodynamic stabilization through alteration of the Gibbs free energy via the largely overlooked PΔV term.

在卤化钙钛矿半导体中混合碘化物和溴化物是调节其带隙的有效策略。因此，混合卤化物钙钛矿对色彩可调的LED和串联太阳能电池具有广阔的前景。然而，混合卤化物钙钛矿的带隙在（太阳）光下是不稳定的，因为卤化物分离成不同带隙的区域。使用压力相关的超快速瞬态吸收光谱法，我们发现较高的外部压力增加了稳定卤化物混合比的范围。通过插入较小的阳离子，化学压缩具有相同的效果，这意味着可以通过调整晶体体积和可压缩性来稳定任何碘化物：溴化物的比率。我们将这些发现解释为通过大大忽略了吉布斯自由能而增加了热力学稳定性P Δ V术语。