Charge diffusion and interface limited charge extraction in hybrid perovskite thin films

The extraction of charge from perovskite solar cells requires charge diffusion to a charge extraction layer (e.g. PEDOT:PSS), followed by charge extraction. We present a method based on time-resolved luminescence to measure charge diffusion and extraction. We find that hole transfer from methylammonium lead iodide (MAPI) to PEDOT:PSS limits the hole extraction rate, and that faster extraction is obtained by using NiO as a hole extraction layer. In addition we observe a very high hole diffusion coefficient of 2.2 cm2/s in a solution-processed MAPI film that is independent of charge density, suggesting a band-like regime of hole transport.