Enhanced photoelectric performance of inverted CsPbI2Br perovskite solar cells with zwitterion modified ZnO cathode interlayer

Abstract All-inorganic perovskite solar cells (PSCs) are attracting more attention due to potential superior stability than organic-inorganic hybrid PSCs. Electrode Interface plays an important role in achieving efficient performance and high stability of the devices. Here, zwitterionic molecules 3-triphenylphosphaniumylpropane-1-sulfonate are adopted to modify ZnO cathode interlayer in inverted CsPbI2Br PSCs. By which, defects on ZnO surface and at the interface of CsPbI2Br/ZnO are passivated. More efficient electron extraction from perovskite to cathode is achieved due to enhanced charge transfer and suppressed charge recombination at the interface. Simultaneously, desirable energy level alignment at the cathode contact is formed. Consequently, superior optoelectronic device performance and stability are accomplished. Hugely improved champion efficiency of 14.62% is achieved with VOC up to 1.25 V and FF of 76.83%, compared with the control device (PCE of 12.03%, VOC of 1.168 V and FF of 66.58%). The optimized device remains ~80% of its initial efficiency for 32 days under illumination and for 18 days stored in ambient air.