Electronic Structures and Photovoltaic Properties of Copper-, Sodium- and Ethylammonium-Added CH₃NH₃PbI₃ Perovskite Compound

Abstract

Copper, alkali metals, and organic cations were added to perovskite precursor solutions to enhance the photovoltaic conversion properties and durability of perovskite solar cells. Device properties were improved by the co-addition of copper and sodium. The enhancement of open-circuit voltage by bromine substitution also contributed to the improvement of conversion efficiency. First-principles calculations indicated that the energy levels derived from the Cu d orbital would function as an acceptor level. While the conversion efficiency of the device increased, the durability of the device decreased. Considering the results of the first-principles calculation, the decrease in device durability was attributed to the instability of the crystal structure due to the Cu and sodium substitutions. To enhance the crystal stability, ethylammonium was introduced as a stable organic cation, and the addition of ethylammonium to the perovskite precursor solution significantly enhanced the device’s durability while maintaining conversion efficiency.

Keywords

• copper
• sodium
• ethylammonium
• first-principles calculations
• perovskite
• solar cell