Hybrid halide perovskites have great potential for application in optoelectronic devices. However, an understanding of some basic properties, such as charge-carrier transport, remains inconclusive, mainly due to the mixed ionic and electronic nature of these materials. Here, we perform temperature-dependent pulsed-voltage space-charge-limited current measurements to provide a detailed look into the electronic properties of methylammonium lead tribromide (${\mathrm{MA}\mathrm{Pb}\mathrm{Br}}_3$) and methylammonium lead triiodide (${\mathrm{MA}\mathrm{Pb}\mathrm{I}}_3$) single crystals. We show that the background carrier density in these crystals is orders of magnitude higher than that expected from thermally excited carriers from the valence band. We highlight the complexity of the system via a combination of experiments and drift-diffusion simulations and show that different factors, such as thermal injection from the electrodes, temperature-dependent mobility, and trap and ion density, influence the free-carrier concentration. We experimentally determine effective activation energies for conductivity of (349 ± 10) meV for ${\mathrm{MA}\mathrm{Pb}\mathrm{Br}}_3$ and (193 ± 12) meV for ${\mathrm{MA}\mathrm{Pb}\mathrm{I}}_3$, which includes the sum of all of these factors. We point out that fitting the dark current density-voltage curve with a drift-diffusion model allows for the extraction of intrinsic parameters, such as mobility and trap and ion density. From simulations, we determine a charge-carrier mobility of 12.9 cm${}^2$/Vs, a trap density of 1.52 × 10${}^{13}$ cm${}^{-3}$, and an ion density of 3.19 × 10${}^{12}$ cm${}^{-3}$ for ${\mathrm{MA}\mathrm{Pb}\mathrm{Br}}_3$ single crystals. Insights into charge-carrier transport in metal-halide perovskite single crystals will be beneficial for device optimization in various optoelectronic applications.

中文翻译：

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了解金属卤化物钙钛矿单晶中的暗电流电压特性

混合卤化物钙钛矿在光电器件中具有巨大的应用潜力。但是，主要由于这些材料具有混合的离子和电子性质，因此对某些基本特性（例如，载流子传输）的理解仍然不确定。在这里，我们执行与温度相关的脉冲电压，空间电荷受限的电流测量，以详细了解甲基溴化三铵铅（${嘛\mathrm{铅含量}溴}_3$）和甲基碘化三碘化铅（${嘛\mathrm{铅含量}\mathrm{一世}}_3$）单晶。我们表明，这些晶体中的本底载流子密度比价带中热激发载流子的期望载流子密度高几个数量级。我们通过结合实验和漂移扩散模拟来强调系统的复杂性，并表明不同的因素（例如，电极的热注入，与温度有关的迁移率以及陷阱和离子密度）会影响自由载流子浓度。我们通过实验确定了电导率为（349±10）meV的有效激活能${嘛\mathrm{铅含量}溴}_3$ 和（193±12）meV ${嘛\mathrm{铅含量}\mathrm{一世}}_3$，其中包括所有这些因素的总和。我们指出，用漂移扩散模型拟合暗电流密度-电压曲线可以提取固有参数，例如迁移率，陷阱和离子密度。通过仿真，我们确定12.9 cm的载流子迁移率${}^2$/ Vs，陷阱密度为1.52×10${}^{13}$ 厘米${}^{-3}$，离子密度为3.19×10${}^{12}$ 厘米${}^{-3}$ 对于 ${嘛\mathrm{铅含量}溴}_3$单晶。深入了解金属卤化物钙钛矿单晶体中的载流子传输将有助于各种光电应用中的器件优化。