Effects of co-addition of copper, sodium and ethylammonium to CH<sub>3</sub>NH<sub>3</sub>PbI<sub>3</sub> perovskite compound

From the band calculation, the copper d-orbital band formed slightly above the valence band maximum would function as an acceptor level promoting the generation of carriers. In addition, the excitation processes from the p-orbital of iodine and the d-orbital of copper to the s-orbital of sodium could suppress carrier recombination. Total energy calculations showed that, the stability of the crystal structure decreases with the addition of copper and sodium, but increases with the addition of ethylammonium. Therefore, it is expected that the combination of these compounds can compensate for the disadvantage of unstable crystal structure. The calculated results could be obtained by optimizing the composition of the perovskite and the annealing conditions.