In the present paper, a phenomenon of ionic migration of large organic cations in the lead- and iodide-deficient perovskite films is unveiled. This phenomenon is intrinsic to the structure and at the origin of a large hysteresis in the measured J–V curves. Contrary to iodide, it cannot be fully blocked through defect passivation by potassium ions.
Halide perovskite solar cells are characterized by a hysteresis between current–voltage (J–V) curves recorded on the reverse and on the forward scan directions, and the suppression of this phenomenon has focused great attention. In the present work, it is shown that a special family of 3D perovskites, that are rendered lead -and iodide- deficient (d-HPs) by incorporating large organic cations, are characterized by a large hysteresis. The strategy of passivating defects by K+, which has been successful in reducing the hysteresis of 3D perovskite perovskite solar cells, is inefficient with the d-HPs. By glow discharge optical emission spectroscopy (GD-OES), the existence of the classic iodide migration in these layers is unveiled, which is efficiently blocked by potassium cation insertion. However, it is also shown that it co-exists with the migration of the large organic cations characteristics of d-HPs which are not blocked by the alkali metal ion. The migration of those large cations is intrinsically linked to the special structure of the d-HP. It is suggested that it takes place through channels, present throughout the whole perovskite layer after the substitution of PbI+ units by the large cations, making this phenomenon intrinsic to the original structure of d-HPs.
Liam Gollino, Daming Zheng, Nicolas Mercier, Thierry Pauporté*
How to cite:
L. Gollino, D. Zheng, N. Mercier, T. Pauporté, Exploration 2023, 4, 20220156.