Fig. 3

Optical absorption of Cs₄PbBr₆ NCs with increasing pressure. a Typical profile of the absorption band for Cs₄PbBr₆ NCs at different pressures measured in situ in a DAC apparatus. The dashed arrows indicate the shift of the bound exciton absorption peaks of E_ex1 and E_ex2. b Absorption spectra of Cs₄PbBr₆ NCs measured at a selected pressure of 6.17 GPa. E_ex1 and E_ex2 represent the splitting bound exciton absorption peaks. c Pressure dependence of energy difference ΔE deduced from the difference of E_ex1 and E_ex2