A long photoluminescence decay lifetime has been regarded as a generic indication of long charge carrier recombination lifetime in semiconductors such as metal halide perovskites (MHPs), which have shown tremendous success in solar cells. Here, we report that MHP polycrystalline films with extrinsic metal ions have a very long charge recombination lifetime, but a much shorter photoluminescence decay lifetime, and this huge difference can be explained by a model of lateral homojunction within each individual grain. The lateral homojunction is formed due to the doping along grain boundaries by metal ions, and then verified by nanoscale potential mapping and transient photo-response mapping. The built-in electric field within each grain reduces the recombination of free charge carriers within the perovskite grain and along grain boundaries, while the free electrons and holes are collected to cathode and anode through the grain boundaries and grain interiors, respectively. Then, the efficiencies of MHP polycrystalline solar cells are increased.

较长的光致发光衰变寿命已被认为是半导体（例如金属卤化物钙钛矿（MHP））中较长的载流子复合寿命的一般指示，这在太阳能电池中已显示出巨大的成功。在这里，我们报道具有外在金属离子的MHP多晶膜具有很长的电荷复合寿命，但是光致发光衰减寿命却短得多，并且这种巨大的差异可以用每个晶粒内的横向同质结模型来解释。由于金属离子沿晶界掺杂而形成横向同质结，然后通过纳米级电势映射和瞬态光响应映射进行验证。每个晶粒内的内置电场减少了钙钛矿晶粒内以及沿晶界的自由电荷载流子的复合，而自由电子和空穴分别通过晶界和晶粒内部被收集到阴极和阳极。然后，提高了MHP多晶太阳能电池的效率。