Key Takeaways & Executive Findings
- •• Quasi-2D perovskites combine the stability of 2D and efficiency of 3D perovskites, offering a promising route for next-generation photovoltaics. • The review highlights structural advantages and challenges of quasi-2D perovskites, including Ruddlesden-Popper and Dion-Jacobson phases. • Unique additive methods specific to quasi-2D perovskites are suggested to enhance device performance and stability. • Material and device analysis using Ruddlesden-Popper, Dion-Jacobson, and alternating cation phases are discussed to provide engineering insights.
Abstract
Quasi-two-dimensional (2D) perovskite embodies characteristics of both three-dimensional (3D) and 2D perovskites, achieving the superior external environment stability structure of 2D perovskites alongside the high efficiency of 3D perovskites. This effect is realized through critical structural modifications in device fabrication. Typically, perovskites have an octahedral structure, generally ABX3, where an organic ammonium cation (A’) participates in forming the perovskite structure, with A’(n) (n = 1 or 2) sandwiched between A(n-1)B(n)X(3n+1) perovskite layers. Depending on whether A’ is a monovalent or divalent cation, 2D perovskites are classified into Ruddlesden-Popper perovskite or Dion-Jacobson perovskite, each generating different structures. Although each structure achieves similar effects, they incorporate distinct mechanisms in their formation. And according to these different structures, various properties appear, and additive and optimizing methods to increase the efficiency of 3D perovskites also exist in 2D perovskites. In this review, scientific understanding and engineering perspectives of the quasi-2D perovskite is investigated, and the optimal structure quasi-2D and the device optimization is also discussed to provide the insight in the field.
1. Introduction
Perovskites have gained significant attention in the semiconductor field due to their ability to form thin films through solution process from precursors, making the fabrication process both cost-effective and straightforward [1–4]. Over the past few decades, perovskite technology has advanced rapidly, achieving a power conversion efficiency (PCE) of 26.7% in solar cells [5]. With remarkable advancements in the field of perovskite solar cells (PSCs), perovskites have potential in various applications such as light-emitting diodes (LEDs), thin-film field-effect transistors (TFTs), and image sensors [6–18]. Additionally, the tunability of the bandgap allows perovskites to absorb a wide range of wavelengths, facilitating the development of high-efficiency tandem solar cells by integrating perovskites with both narrow and wide bandgaps [19–26].
However, these advantages are significantly undermined by the vulnerability of perovskites to ambient environmental conditions. The most widely used perovskites are organic halide perovskites (OHPs) [27, 28], typically composed of an organic cation (A), a metal cation (B), and a halide anion (X). The metal cations (B) are hydrophilic and highly susceptible to moisture in the air, while the halide anions are prone to ion migration under light exposure. These stability issues related to moisture and light significantly reduce the efficiency and lifetime of perovskite devices, posing substantial challenges to their commercialization [29–33].
To address these stability challenges, extensive research has focused on inserting organic ammonium cations (A’) as spacers within the ABX3 structure. These A’ cation spacers act as barriers, reducing exposure to the external environment and increasing exciton binding energy through the quantum well (QW) effect [34–39]. This enhances both overall stability and the open circuit voltage (Voc) [40–43]. Additionally, spacer cations integrated during the annealing process contribute to the film’s flexibility, reducing defects and improving performance. The promising results of this approach have spurred significant interest in quasi-2D perovskites, which incorporate 2D structures into traditional 3D perovskites. These 2D perovskites are categorized into Ruddlesden-Popper (RP) and Dion-Jacobson (DJ) phases based on the nature of the spacer cation [44–46].
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Hyeonseok Lee, Taeho Moon, Younghyun Lee, Jinhyun Kim (2025). Structural Mechanisms of Quasi-2D Perovskites for Next-Generation Photovoltaics. Nano-Micro Letters. https://doi.org/10.1007/s40820-024-01609-9
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Frequently Asked Questions
What are quasi-2D perovskites?
Quasi-2D perovskites are materials that combine the stability of 2D perovskites with the high efficiency of 3D perovskites. They are formed by inserting organic ammonium cations as spacers between perovskite layers, creating a quantum well structure that enhances stability and open-circuit voltage.
What are the main types of quasi-2D perovskites?
The main types are Ruddlesden-Popper (RP) and Dion-Jacobson (DJ) phases, which differ based on the spacer cation: RP uses monovalent cations, while DJ uses divalent cations. These structural differences affect crystal packing, stability, and charge transport.
Why are quasi-2D perovskites important for photovoltaics?
They offer improved environmental stability compared to 3D perovskites while maintaining high power conversion efficiency. This makes them promising for next-generation solar cells that need to withstand real-world conditions.
What are the challenges of quasi-2D perovskites?
Challenges include reduced charge-carrier transport due to insulating organic spacers, and the need for precise control of the quantum well thickness to balance efficiency and stability. Additive engineering and optimized fabrication are being explored to overcome these issues.
What is the significance of the quantum well effect in quasi-2D perovskites?
The quantum well effect increases exciton binding energy, which can enhance open-circuit voltage and stability. However, it can also hinder charge separation, so careful design is needed to optimize device performance.
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