a, Detailed device photovoltaic parameters (open-circuit voltage (Voc), short-circuit current density (Jsc), fill factor (FF) and power conversion efficiency (PCE)) from both reverse and forward J–V curves shown in Fig. 3a. b, Statistics of photovoltaic parameters of devices with and without the Pb-sequestering layers. Twelve devices were used for each type of device configuration. Error bars show the mean value, maximum/minimum values, and 25–75% region of data, which are represented by the circle, top/bottom bars, and rectangle, respectively.