Enhanced stability of Ge-doped CsPb(I1−xBrx)3 perovskite solar cells

Abstract

All-inorganic CsPb(I_1−xBr_x)₃ perovskite solar cells (PSCs) have continuously broken record power conversion efficiency (PCE); however their poor stability in humid environments is still a serious bottleneck. To suppress the humidity-induced rapid transformation from the black phase into the yellow phase, germanium (Ge) doping is introduced to improve the tolerance factor of CsPb_1−xGe_xI_2.85Br_0.15 and its photoelectric performance. A combined investigation of the structural and optical properties reveals a successful substitution of lead (Pb) with Ge in the films as well as a champion PCE of 19.70% for a 1% Ge doped PSC. More significantly, the Ge doped device retained 91.5% of its initial efficiency after being stored in air for 500 hours without any encapsulation process, in contrast to the 83.7% for its undoped counterpart.