Spatially Heterogeneous Chlorine Incorporation in Organic−Inorganic Perovskite Solar Cells

Citation:

Yanqi Luo, Shany Gamliel, Sally Nijem, Sigalit Aharon, Martin Holt, Benjamin Stripe, Volker Rose, Mariana I. Bertoni, lioz etgar, and David P. Fenning. 2016. “Spatially Heterogeneous Chlorine Incorporation in Organic−Inorganic Perovskite Solar Cells.” Chemistry of Materials, 18, 2016,28: 6536–6543.

Abstract:

Spatial heterogeneities in the chemical makeup of thin film photovoltaic devices are pivotal in determining device efficiency. We report the in-plane spatial distribution and degree of chlorine incorporation in organic−inorganic lead halide perovskite absorbers by means of nondestructive synchrotronbased nanoprobe X-ray fluorescence. The presence of chlorine is positively identified in CH3NH3PbI3 films synthesized with Clcontaining precursors and as an impurity in some films synthesized with nominally Cl-free precursors. The impurity may be introduced from precursors or as contaminants during film synthesis. The films formed from Cl-containing precursors contain roughly an order of magnitude higher amount of chlorine, with Cl:I values greater than 0.02 found whether Cl is present in either the organic or the inorganic precursor for both one- and two-step fabrication processes. A spatial variation in the Cl incorporation is observed within single particles and as well as between particles within a given film, and the standard deviation of the Cl:I ratio across the films is up to 30% of the average
value. Understanding and controlling the heterogeneous distribution of chlorine in hybrid perovskite layers may offer a path to improve their photovoltaic performance.