Extended Data Fig. 1: Evidence of negatively charged SWCNT after filling perovskite.

a, Density of states of CsPbI3@(20,0)-SWCNT and projected density of states of (20,0)-SWCNT and [Cs4PbI5]. Fermi levels of CsPbI3@(20,0)-SWCNT and empty (20,0)-SWCNT are labelled, which is calculated by HSE06 functional. b, Raman spectra showing G band of CsPbI3@SWCNT and empty-SWCNT. Excitation wavelength: 532 nm.