Strain or Electronic Effects? - The Influence of Alkali Metals on the Bandgap of Cu2O

Using density functional theory we studied the influence of group 1 and 11 impurities on the bandgap of Cu2O. Our results show that dopants affect the bandgap through geometric and electronic effects. Geometric effects originate from the compression of adjacent Cu-O bonds while electronic effects are tightly connected to changes in the ability to delocalize electrons through 2 electron 3 center bonds. Doping with alkali metals disturbs the delocalization network and therefore results in an increased bandgap. The 2 electron 3 center bonding network network is restored by Au and Ag dopants or decreased doping concentrations.