Blading Phase‐Pure Formamidinium‐Alloyed Perovskites for High‐Efficiency Solar Cells with Low Photovoltage Deficit and Improved Stability

• DOI: 10.1002/adma.202000995
• Publication Date: 2020-05-29T05:41:58Z
• Authors: Wu‐Qiang Wu; Peter N. Rudd; Qi Wang; Zhibin Yang; Jinsong Huang
• Keywords: Formamidinium; Photocurrent; Passivation

Currently, blade-coated perovskite solar cells (PSCs) with high power conversion efficiencies (PCEs), that is, greater than 20%, normally employ methylammonium lead tri-iodide a sub-optimal bandgap. Alloyed perovskites formamidinium (FA) cation have narrower bandgap and thus enhance device photocurrent. However, FA-alloyed show low phase stability moisture sensitivity. Here, it is reported incorporating 0.83 molar percent organic halide salts (OHs) into inks enables phase-pure, highly crystalline extraordinary optoelectronic properties. The OH molecules modulate the crystal growth, stability, passivate ionic defects at surface and/or grain boundaries, of film. A efficiency 22.0% under 1 sun illumination for PSCs demonstrated an open-circuit voltage 1.18 V, corresponding to very small deficit 0.33 significantly improved operational 96% initial retained one 500 h.