Berlin 2018 – wissenschaftliches Programm
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CPP: Fachverband Chemische Physik und Polymerphysik
CPP 72: Hybrid and Perovskite Photovoltaics I
CPP 72.7: Vortrag
Donnerstag, 15. März 2018, 17:00–17:15, C 264
Reducing recombination and enhancing open circuit voltage by Strontium-alloying in multiple cation perovskite solar cells — •Pietro Caprioglio1,3, Fengshuo Zu2, Christian M. Wolff1, Martin Stolterfhot1, Norbert Koch2, Bernd Rech3, Steve Albrecht3, and Dieter Neher1 — 1University of Potsdam — 2Humboldt-Universität, Berlin — 3Helmholtz-Zentrum Berlin
State of the art perovskite solar cells still suffer from too low fill factor and open circuit voltage (Voc), which has been related to non-radiative losses mostly happening at the surface. Here, we present the enhancement of the Voc by addition of Strontium (Sr) to a quadruple cation perovskite Rb5(Cs5(MA0.17FA0.83)Pb(I0.83 Br0.17)3)95)95. The resulting material displays significantly enhanced photoluminescence (PL) lifetime and absolute PL yield together with a larger splitting of the quasi-Fermi levels. These findings are confirmed by the increase in Voc and in electroluminescence efficiency observed in actual devices. As a result, the power conversion efficiency increases, reaching a PCE of 20.3% under AM1.5G illumination. We show through various photoelectron spectroscopy techniques (UPS/XPS and IPES), how the addition of Sr induces a more n-type surface and enables better contact selectivity. Such a change in energetics is responsible for a substantial suppression of surface and interface recombination. Morphology characterization shows that Sr is mostly segregated close to the charge transport layers, affecting only the interfaces. In conclusion, we propose that Sr-addition enables an appropriate interface modification that helps to reduce Voc losses.