Lead-less mesoscopic perovskite solar cells with enhanced photovoltaic performance by strontium chloride substitution

Abstract The substitution of toxic lead (Pb) in efficient perovskite solar cells (PSCs) is a key problem for commercialization. In this paper, strontium chloride (SrCl2)-doped lead-less PSCs were constructed successfully, and the effect of Sr substitution on the perovskite film formation and its photovoltaic property was investigated in detail by X-ray diffraction (XRD), scanning electron microscopy (SEM), UV–visible absorption, time-resolved photoluminescence (TRPL), X-ray photoelectron spectroscopy (XPS) and electrochemical impedance spectroscopy (EIS) analyses. It is demonstrated that the introduction of Sr substitution changes the chemical composition of PbI2 precursors and reduces the excess PbI2 in the perovskite films. A 10 mol% Sr substitution in the PbI2 precursor solution can increase the absorbance of the resultant perovskite film and enhance the electron extraction at the “perovskite/TiO2” interface, thus increasing the device's short-circuit current density (Jsc) from 17.41 mA cm-2 to 19.45 mA cm-2. At the same time, Sr substitution can reduce the charge combination in the PSC, which allows the PSC to obtain a higher open-circuit voltage (Voc) of 1.08 V and fill factor (FF) of 0.74. Finally, the PSC prepared with 10 mol% Sr substitution exhibits a considerable power conversion efficiency (PCE) of 15.64%, showing an improvement of 18.9% compared to that of the pristine device.