fig4

Figure 4. Extrinsic doping for perovskite homojunctions. (A, B) A simple heterovalent metal halide surface treatment strategy enables the self-assembly of an n/n⁺ perovskite homojunction, which synergistically enlarges the built-in electric field. Reproduced from Lu et al.^[43]. (C) Schematic process of Ar⁺ bombardment to induce an n-type perovskite. Reproduced from Ren et al.^[45].