Cd-Doped Triple-Cation Perovskite Thin Films with a 20 mu s Carrier Lifetime

Triple-cation mixed-halide perovskite of composition Cs-x(FA(y)MA(1-y))(1-x)Pb(IzBr1-z)(3) (denoted as FAMACs) is a promising optoelectronic material due to many attractive optoelectronic properties. Reducing the defect density in FAMACs polycrystalline thin films is critical for the improvement of their photovoltaic performance. Herein, we report that by incorporating CdCl2 into FA(0.9)MA(0.05)Cs(0.05)PbI(2.7)Br(0.3) polycrystalline films, the bulk carrier lifetime is prolonged to similar to 20 mu s, similar to that in single crystals, and the intrinsic surface defect density is reduced to as low as (6.72 +/- 0.01) x 10(13) cm(-3). The incorporation of CdCl2 leads to an increase of power conversion efficiency (PCE) of FAMACs solar cell from 20.4% to 22.1%, which is attributed to a larger V-oc due to the removal of bulk defects by Cd ions doping and Cl-ion-assisted crystallization. However, further improvement of PCE is likely limited by the interface defects produced during the deposition of the charge transport layer in constructing solar cells.