Efficient planar perovskite solar cells using halide Sr-substituted Pb perovskite

Stability and lead toxicity issues of inorganic organic halide lead perovskite solar cells have significantly limited their commercial applications. The nontoxic strontium (Sr) can be a good candidate to reduce lead utilization due to their similar ionic radiuses. Here we uncovered the dramatic influence of Sr element substitution on the optoelectronic properties of perovskite films, including up-shifting conduction band edge energy level, increasing exciton binding energy and trap density states due to the isoelectronic impurity of electric neutral substitution. The incorporation of a small content of Sr (a≤0.05) into the CH3NH3SraPb1−aI3−xClx crystal lattice can act positively impact on material thermal stability and solar cell device output voltage (~1.11 V). An overall highly photovoltaic efficiency of ~16.3% was achieved with a planar n-i-p structure of ITO/compact TiO2/CH3NH3SraPb1−aI3−xClx/spiroMeOTAD/Au. Impedance characterization reveals an increased trap states induced by substitution Pb with Sr in the hybrid halide perovskites, and thus provide a deep understanding of the role of external elements on device physics.