Unveiling of a puzzling dual ionic migration in lead- and iodide-deficient halide perovskites (d-HPs) and its impact on solar cell J–V curve hysteresis

Abstract

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 presentwork, 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 3Dperovskite perovskite solar cells, is inefficientwith the d-HPs. By glowdischarge 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 themigration 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.

Keywords

glowdischarge optical emission spectroscopy / halide perovskite / hysteresis / iodide-deficiency / ionic migration / lead-deficiency / solar cells

RIGHTS & PERMISSIONS

2023 2023 The Authors. Exploration published by Henan University and John Wiley & Sons Australia, Ltd.