Quantum mechanics/molecular mechanics studies on the photoprotection mechanisms of three chalcones

•Photophysical properties of the three chalcones were evaluated by QM/MM method.•Absorption spectra of EDDP, EDPO, and EDHP covered the whole UV region.•Geometric structure twisting in glycerol solvent weaken their fluorescence strength.•After-sun repair abilities of the three molecules improved upon photoexcitation.•Three chalcones both possess full-band UV protection and after-sun repair abilities.