We investigate the origins of exceptionally long charge-carrier lifetimes of halide perovskites by using temperature-dependent and time-resolved mid-infrared spectroscopy. We report direct observations of large polarons through their distinct mid-infrared electronic transitions and quantitatively correlate their formation with enhancement of electron-phonon coupling that quenches photoluminescence. The temperature-dependent study reveals a branching between free-carrier and large-polaron states in association with thermally induced dynamic disorder of the anharmonic inorganic framework, which is examined through local vibrational modes of the perovskite films. This dynamic disorder localizes charge carriers and enhances electron-phonon coupling, which both quenches photoluminescence and promotes large-polaron formation. Fortunately, such localization extends the charge recombination lifetime by nearly an order of magnitude. This work highlights the interplay between charge-carrier mobility and lifetime and suggests design rules about how cation and anion substitution can be used to tune the structural dynamics that underpin their relationship.

我们通过使用温度依赖性和时间分辨的中红外光谱技术研究了卤化物钙钛矿的超长电荷载流子寿命的起源。我们报告了通过其独特的中红外电子跃迁对大极化子的直接观察，并定量地将它们的形成与电子声子耦合的增强相结合，从而终止了光致发光。依赖温度的研究揭示了与非感应无机骨架的热诱导动态紊乱相关的自由载流子态和大极化子态之间的分支，这是通过钙钛矿薄膜的局部振动模式来检查的。这种动态紊乱使电荷载流子局部化，并增强了电子-声子耦合，这既可以抑制光致发光，又可以促进大极化子的形成。幸运的是，这种局部化将电荷复合寿命延长了近一个数量级。这项工作强调了载流子迁移率和寿命之间的相互作用，并提出了有关如何使用阳离子和阴离子取代来调节支撑它们之间关系的结构动力学的设计规则。