Stability Characterization of PbI2-Added CH3NH3PbI3- xCl x Photovoltaic Devices

Naoki Ueoka; Takeo Oku

doi:10.1021/acsami.8b16029

Stability Characterization of PbI₂-Added CH₃NH₃PbI_{3- x}Cl _x Photovoltaic Devices

ACS Appl Mater Interfaces. 2018 Dec 26;10(51):44443-44451. doi: 10.1021/acsami.8b16029. Epub 2018 Dec 12.

Authors

Naoki Ueoka¹, Takeo Oku¹

Affiliation

¹ Department of Materials Science , The University of Shiga Prefecture , 2500 Hassaka , Hikone , Shiga 522-8533 , Japan.

PMID: 30540175
DOI: 10.1021/acsami.8b16029

Abstract

The stability of TiO₂/CH₃NH₃PbI_{3- x}Cl _x-based photovoltaic devices in ambient air was evaluated upon adding PbI₂ and/or PbCl₂. X-ray diffraction (XRD) peak intensities corresponding to the perovskite phase were increased by adding PbI₂. After 7 weeks, the XRD peak intensities corresponding to the perovskite phase decreased and those corresponding to PbI₂ increased. The reaction rate constants for the decomposition of perovskite and formation of PbI₂ were estimated from these data. Thermodynamic calculations of the reaction between PbCl₂ and I₂ suggested that the formation of PbI₂ was not related to the added PbCl₂ but rather to excess PbI₂. Open-circuit voltages and fill factors of the devices were improved with the 7 week time lapse because of the suppression of electron-hole recombination by the PbI₂. In addition, the decomposition of perovskite grains was suppressed by the added PbI₂. The I content of the perovskite phase decreased with the 7 week time lapse. However, the Cl content was largely constant after the 7 weeks, which suggested that Cl doping effectively stabilized the perovskite photovoltaic devices.

Keywords: CH3NH3PbI3−xClx; PbI2; perovskite; photovoltaic device; stability.