The effect of oxygen molecule adsorption on lead iodide perovskite surface by first-principles calculation

• Published in: Applied surface science 2018-01, Vol.428, p.140-147
• Main Authors: Ma, Xia-Xia, Li, Ze-Sheng
• Format: Article
• Language: English
• Subjects: Electron transfer; Oxygen molecule adsorption; Perovskite solar cell; Work function
• ISSN: 0169-4332; 1873-5584
• DOI: 10.1016/j.apsusc.2017.09.073

The flat bands appearing in adsorbed system hinders the electron transfer from perovskite to electron extract layer. [Display omitted] •The reason why work function increases when O2 is adsorbed on the surface of MAPbI3 is elucidated.•The formation of O2− is easy because unoccupied 2π* orbitals of O2 are located between VB and CB of the MAPbI3 perovskite.•Physisorption of O2 can slightly affect the band structure of MAPbI3, thus reducing the PCE of MAPbI3 perovskite solar cell. Oxygen molecule has a negative effect on perovskite solar cells, which has been investigated experimentally. However, detailed theoretical research is still rare. This study presents a microscopic view to reveal the interaction mechanism between O2 and perovskite based on the first-principles calculation. The results show that O2 is adsorbed on the (100) surface of MAPbI3 perovskite mainly by Van der Waals force. O2 adsorption makes the MAPbI3 surface generate a small number of positive charges, which leads to the increase of the work function of the MAPbI3 surface. This is in agreement with the experimental measurement. And increased work function of MAPbI3 surface is not beneficial to electron transfer from perovskite to electronic extraction layer (such as TiO2). Comparison of the density of states (DOS) of the clean (100) surface and the adsorbed system shows that an in-gap state belonging to O2 appears, which can explain the phenomenon observed from experiments that electron transfers from the surface of perovskite to O2 to form superoxide. The theoretical power conversion efficiency of the system with and without O2 adsorption is evaluated, and it turns out that the power conversion efficiency of the system with O2 adsorption is slightly lower than that of the system without O2 adsorption. This result indicates that avoiding the introduction of O2 molecules between perovskite and electronic extraction layer is beneficial to the perovskite solar cell.