Energy-band gradient halide perovskites are highly desired candidates for fabricating high performance optoelectronic devices. Here, it is shown that a mixed halide perovskite single crystal undergoes phase segregation in the longitudinal direction under abovebandgap light illumination, generating a micron-thick layer with vertically gradient halide composition and thus graded valence band edge at the crystal surface.
- Zelong Chen
- Zhiya Dang
- Pingqi Gao
