Significant effort is being devoted to the search for all-inorganic Pb-free halide perovskites (HPs) for photovoltaic applications. However, candidate HPs that combine all the desirable attributes — ease of synthesis, favorable bandgaps, outstanding optoelectronic properties, high stability, no toxicity — are extremely rare. Here, we demonstrate experimentally the promise of cesium titanium(IV) bromide (Cs₂TiBr₆), a part of the Ti-based vacancy-ordered double-perovskite halides family, in perovskite solar cells (PSCs). We show, for the first time, that high-quality Cs₂TiBr₆ thin films can be prepared through a facile low-temperature vapor-based method. These films exhibit a favorable bandgap of ∼1.8 eV, long and balanced carrier-diffusion lengths exceeding 100 nm, suitable energy levels, and superior intrinsic and environmental stability. The first demonstration of Cs₂TiBr₆ thin films-based PSCs shows stable efficiency of up to 3.3%. Insights into the Cs₂TiBr₆ film-formation mechanisms and the PSC device operation are provided, pointing to directions for improving Ti-based PSCs.

人们正致力于寻找用于光伏应用的全无机无铅卤化物钙钛矿（HPs）。但是，结合所有理想属性（易于合成，良好的带隙，出色的光电性能，高稳定性，无毒性）的候选HP非常罕见。在这里，我们通过实验证明了钙钛矿型太阳能电池（PSC）中溴化铯铯（IV）（Cs ₂ TiBr ₆）的前景，这是一种基于Ti的空位有序双钙钛矿卤化物家族。我们首次展示了高质量的Cs ₂ TiBr ₆薄膜可以通过简便的基于低温蒸气的方法制备。这些薄膜具有约1.8 eV的良好带隙，超过100 nm的长且平衡的载流子扩散长度，合适的能级以及优异的固有和环境稳定性。基于Cs ₂ TiBr ₆薄膜的PSC的首次展示显示出高达3.3％的稳定效率。提供了对Cs ₂ TiBr ₆成膜机理和PSC器件操作的见解，指出了改进Ti基PSC的方向。