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HL: Fachverband Halbleiterphysik

HL 55: Perovskite and Photovoltaics III (joint session HL/KFM)

HL 55.12: Vortrag

Freitag, 22. März 2024, 12:30–12:45, EW 203

The detrimental role of PbI2 at the interface between absorber and electron-transport layer in halide-perovskite solar cells — •Dan Ralf Wargulski, Ke Xu, Steve Albrecht, and Daniel Abou-Ras — Helmholtz-Zentrum Berlin für Materialien und Energie, Berlin, Germany

There is an ongoing discussion in the halide-perovskite community about the beneficial or harmful effects of PbI2 in halide-perovskite solar cells (HPSCs). One school praises PbI2 for its passivating and stabilizing properties, while the other aims at getting rid of excess PbI2, because it leads to decreased cell efficiencies and degraded long-term stability. How can such a contradiction exist? The effect of PbI2 depends on its location in the solar-cell stack and on the specific HPSC architecture used. When applied as top cells in tandem devices, HPSCs do not exhibit a n-i-p structure but an p-i-n structure, often called *inverted* HPSC structure. As a result, the top surface where PbI2 forms is not situated at the interface between the absorber and the hole-transport layer anymore, but at the interface to the electron-transport layer. This modifies considerably the effects of PbI2 on the device performance. The present work discusses the formation of PbI2 in HPSCs with slot-die-coated, triple-halide perovskite absorbers, which was investigated by means of correlative electron microscopy. Studying the changing PbI2 coverage of the halide-perovskite absorbers with varying annealing temperature, a model will be presented that explains the effects of the PbI2 precipitates on the open-circuit voltages and the fill factors of the HPSCs with inverted cell architecture.

Keywords: Halide perovskites; Lead iodide; Interfaces; Electron microscopy; Solar cells