Manipulated Crystallization and Passivated Defects for Efficient Perovskite Solar Cells via Addition of Ammonium Iodide

Abstract

Organic–inorganic metal halide perovskite materials have been widely studied as the light absorber for efficient photovoltaics. However, perovskite layers with defective nature are typically prepared with an uncontrollable crystallization process, intrinsically limiting further advance in device performance, and thus require delicate manipulation of crystallization processes and defect density. Here, we demonstrate an ammonium-assisted crystallization of perovskite absorbers during a two-step deposition to fabricate efficient solar cells. Addition of ammonium iodide (NH4I) is devised to manipulate the nucleation and crystal growth of perovskite, wherein the formation and transition of intermediate x[NH4 +]•[PbI3] x− enables high-quality perovskite layers with an enlarged grain and reduced defect density. As a result, the perovskite solar cells (PSCs) achieve an average efficiency of 21.36% with a champion efficiency of 22.15% and improved environmental stability over 30 days in ambient conditions with varied relative humidity. These results with addition of NH4I provide an available and ingenious way to construct high-quality perovskite layers for efficient solar cells and will advance the commercial application of perovskite-based photovoltaics.

When Aggregation‐Induced Emission Meets Perovskites: Efficient Defect‐Passivation and Charge‐Transfer for Ambient Fabrication of Perovskite Solar Cells

“…where Z s is the number of grains per unit area, which is inversely proportional to the grain size. In this study, the C≡N‐based TPE‐TCF molecule partially coordinated PbI 2 in the perovskite precursor solution and formed PbI 2 ⋅TPE‐TCF intermediate (Figure S1), which improved the crystallinity (Figure 4a) and enlarged grain size by retarding the crystallization of perovskite layer [28] . The interaction between TPE‐TCF molecules and PbI 2 in the precursor solution can reduce the nucleation rate and facilitate the perovskite grain growth due to the quick removal of solvents [31] .…”

“…The influence of TPE‐TCF additive on the crystallization rate of the prepared perovskite film was verified by digital photographs of perovskite films (with and without TPE‐TCF additive) after annealing at 100 °C for different times (Figure S2, Supporting Information). The variation in film color indicated that TPE‐TCF addition delayed the crystallization process of the perovskite, which may be an effective method for fabricating high‐quality perovskite film with less defects [27,28] …”

“…The variation in film color indicated that TPE-TCF addition delayed the crystallization process of the perovskite, which may be an effective method for fabricating high-quality perovskite film with less defects. [27,28] As we know, the morphology and structure of the perovskite films are closely related to the performance of PSCs. The improvement effects of TPE-TCF on morphology and structure of perovskite films were studied.…”

Enhanced Thermal Stability of Planar Perovskite Solar Cells Through Triphenylphosphine Interface Passivation

“…[24][25][26] Interfacial engineering between the perovskite absorber and charge transport layers has been widely successful in enhancing the performance and durability of PSCs. [27][28][29] This is due to the tendency for defect or impurity formation at the interfaces, which arises from the sudden change in the lattice structure and crystal orientation. Hence, it is inevitable that a large amount of defects such as undercoordinated lead ion (Pb 2 + ), undercoordinated halides, and dangling bonds are found in these regions.…”

“…Interfacial engineering between the perovskite absorber and charge transport layers has been widely successful in enhancing the performance and durability of PSCs [27–29] . This is due to the tendency for defect or impurity formation at the interfaces, which arises from the sudden change in the lattice structure and crystal orientation.…”