The influences of interfacial recombination loss on the perovskite solar cell performance studied by transient photovoltage spectroscopy

The charge-carrier transport and recombination loss in MAPbI3-based perovskite solar cells (PSCs) have been investigated by transient photovoltage (TPV) spectroscopy measurements. The TPV decays exhibit multi-exponential decay characteristics, where the fast decay seems to be correlated with both the cell performance (J-V characteristics) and the presence of low arc in the Nyquist plot obtained from the intensity-modulated photovoltage spectroscopy (IMVS) measurements. This fast decay exhibits the characteristic of a stretched exponential decay, which is a typical non-simple first-order trapping and recombination process, in the present case, by involving electron transport among defect states on the surface of grain boundaries or interlayer interface. Temperature dependence of TPV decays may also lead to a suggestion that the process can be also accompanied by local lattice distortion. Furthermore, the present experimental data also indicate the interplay between electronic processes in the fast time scale (microseconds in TPV data) and unpaired/mobile ion migration in the slow time scale (hundreds of milliseconds in IMVS data) on the overall cell performance (J-V characteristics). In addition, in practical viewpoints, the results may also demonstrate the potential application of this TPV spectroscopy, in conjunction with IMVS measurement, as a simple tool for identifying the fabricated perovskites solar cells that exhibit a good cell performance with low recombination loss due to surface defect states and ion migration.