Regensburg 2019 – wissenschaftliches Programm
HL 45.8: Poster
Donnerstag, 4. April 2019, 18:30–21:00, Poster E
Impact of precursor stoichiometry on the energetic trap landscape in methylammonium lead iodide perovskite solar cells — •Philipp Rieder1, Andreas Baumann2, and Vladimir Dyakonov1 — 1Experimental Physics VI, Julius Maximilian University of Würzburg, 97074 Würzburg — 2Bavarian Center for Applied Energy Research (ZAE Bayern), 97074 Würzburg
Hybrid organic inorganic perovskite has turned out to be the most promising candidate for highly efficient next generation thin film photovoltaics, amongst others due to its solution processability. Interestingly, the use of slightly non-stoichiometric precursors, typically with a slight excess of lead halide salt, has proven to be essential to achieve the highest efficiencies reported so far. On the contrary, lead halide is known to be the most prominent by-product of film decomposition. In fact, any initial presence of excess lead halide has been linked to an accelerated degradation of the photoactive layer. Here, we study the impact non-stoichiometry of the perovskite layer on the trap landscape of perovskite solar cells in p-i-n layout by means of Thermally Stimulated Current (TSC). We incorporated an increasing amount of lead halide salt in the phenotype of perovskite solar cell absorbers, methylammonium lead iodide. We found that unreacted lead iodide leads to an increase in the density of energetically shallow trap states with an activation energy of around 100 meV. Moreover, we found that the commonly known low temperature phase transition between the orthorhombic and tetragonal crystal phase shifts to even lower temperatures when excess lead iodide is incorporated in the film.