Perovskite semiconductors as the active materials in efficient solar cells exhibit free carrier diffusion lengths on the order of microns at low illumination fluxes and many hundreds of nanometers under 1 sun conditions. These lengthscales are significantly larger than typical junction thicknesses, and thus the carrier transport and charge collection should be expected to be diffusion controlled. A consensus along these lines is emerging in the field. However, the question as to whether the built‐in potential plays any role is still of matter of some conjecture. This important question using phase‐sensitive photocurrent measurements and theoretical device simulations based upon the drift‐diffusion framework is addressed. In particular, the role of the built‐in electric field and charge‐selective transport layers in state‐of‐the‐art p–i–n perovskite solar cells comparing experimental findings and simulation predictions is probed. It is found that while charge collection in the junction does not require a drift field per se, a built‐in potential is still needed to avoid the formation of reverse electric fields inside the active layer, and to ensure efficient extraction through the charge transport layers.

中文翻译：

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关于钙钛矿型太阳能电池需要内置电位的问题

钙钛矿半导体作为高效太阳能电池中的活性材料，在低光照通量下在1个太阳条件下的自由载流子扩散长度约为微米，而在1个太阳光条件下则表现出数百纳米。这些长度尺度明显大于典型的结厚度，因此，应该期望对载流子传输和电荷收集进行扩散控制。这些领域的共识正在这个领域出现。但是，关于内置电位是否发挥任何作用的问题仍是一个推测的问题。使用相敏光电流测量和基于漂移扩散框架的理论器件仿真解决了这个重要问题。尤其是，研究了内置电场和电荷选择性传输层在先进的p–i–n钙钛矿太阳能电池中的作用，对比了实验结果和模拟预测。发现在结中收集电荷本身并不需要漂移场，但仍需要内置电势来避免在有源层内部形成反向电场，并确保通过电荷传输层的有效提取。