Alkali Cation Doping for Improving the Structural Stability of 2D Perovskite in 3D/2D PSCs

Liu, Chang; Sun, Jingsong; Tan, Wen Liang; Lu, Jianfeng; Gengenbach, Thomas R.; McNeill, Christopher R.; Ge, Ziyi; Cheng, Yi‐Bing; Bach, Udo

doi:10.1021/acs.nanolett.9b04661

Cited by 74 publications

(71 citation statements)

References 58 publications

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“…To find out the in-depth reason of the ascending performance of the solar cells, we employed the Mott-Schottky analysis and bias-dependent electrochemical impedance spectroscopy (EIS) to study the interfacial charge transport and recombination behavior. [47][48][49][50] The C −2 verses V characteristics of corresponding devices were obtained by the capacitance-voltage measurement, as illustrated in Figure 4c. The built-in voltages (V bi ) were estimated as 1.00, 0.96, and 0.91 V for TAA-treated, TUtreated, and pristine device, respectively.…”

Section: (7 Of 12)mentioning

confidence: 99%

Manipulation of Perovskite Crystallization Kinetics via Lewis Base Additives

Zhang

et al. 2021

Adv Funct Materials

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The Lewis acid–base adduct approach has been widely used to form high‐crystalline perovskite films, but the complicated crystallization pathway and underlying film formation mechanism are still ambiguous. Here, the detailed crystallization process of perovskites manipulated by Lewis base additives has been revealed by in situ X‐ray scattering measurements. Through monitoring the film formation process, two distinct crystal growth stages have been definitely recognized: i) an intermediate phase‐dominated stage; and ii) a phase transformation stage from intermediates to crystalline perovskite phase. Incorporating Lewis base additives significantly prolongs the duration of stage 1 and induces a postponed phase transformation pathway, which could be responsible for retardant crystallization kinetics. Based on a series of experimental results and theoretical calculations, it is indicated that the manipulation of perovskite crystallization pathway is a result of the modulated molecular interactions between Lewis base additives and solution precursors. Owing to the retardant crystallization kinetics, enhanced‐quality perovskite films with reduced defect density and improved optoelectronic properties, as well as optimized photovoltaic performance have been demonstrated. This work provides in‐depth understanding with respect to perovskite crystallization pathway modulated by Lewis base additives and perceptive guidelines for precise regulation of crystallization kinetics of perovskite film toward high performance.

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Section: (7 Of 12)mentioning

confidence: 99%

Manipulation of Perovskite Crystallization Kinetics via Lewis Base Additives

Zhang

et al. 2021

Adv Funct Materials

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“…In addition to additives interacting with ions or molecules in the solution to affect the crystallization kinetics to improve the crystal orientation, acting as a nucleating agent to promote the nucleation of the gas-liquid interface can also achieve the desired effect, such as KI. [129,130] It may be due to the low density of such additives, which tend to be distributed at the gas-liquid interface and have less solubility in specific solvents. Therefore, it is easy to aggregate and act as a crystal nucleus, inducing the crystallization of perovskite, avoiding the homogeneous nucleation of the film to cause random orientation.…”

Section: Additive Of Precursormentioning

confidence: 99%

Crystallization Kinetics in 2D Perovskite Solar Cells

Wang

Lei

et al. 2020

Advanced Energy Materials

149

124

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volatile decomposition [23] or halide segregation are often observed in hybrid perovskites under various stress conditions (light, [24] thermal, [25] and electric fields [26]); 4) spontaneous phase transition easily occurs for perovskite with unstable crystal structures, particularly for inorganic perovskite. [27-29] To improve the stability of PSCs, researchers attempted numerous methods such as encapsulation, [30] additive engineering, [31] component engineering, [32] etc. [33] However, the PSCs' stability is yet to achieve a perfect solution. Recently, researchers found that the introduction of long-chain organic cations in 3D perovskite as 2D perovskite can block water and oxygen molecules, meanwhile, generate a steric effect to prevent phase transitions, and limit ion migration. [34-36] Hence, fabricating 2D [37,38] or 2D/3D [39-43] mixed perovskite as absorbing layers are effective approaches to improve the stability of PSCs. However, the PCE of 2D PSCs remain lower than that of the 3D ones, which is mainly attributed to the introduction of organic macromolecules that blocks the effective extraction and transport of carriers. [44,45] Fortunately, 2D perovskite usually has three arrangements, namely parallel, perpendicular to the glass substrate or randomly arranged. [46] Manipulating the orientation of the crystal and the phase distribution in the 2D solution-processed perovskite can improve the efficiency and reproducibility of the device. Among them, the most desired arrangement for PSCs is the one that perpendicular to the substrate. Therefore, studying the crystallization kinetics of 2D perovskite is curial to effectively control the film forming process and adjust the crystal orientation (perpendicular to the substrate), which can effectively avoid or reduce the adverse effects of the organic molecular layer and improve device efficiency. [47,48] Nevertheless, few review articles were published on this subject. In this review, we mainly focus on the key issue for controlling crystallization kinetics and summarizing the research progress of their effects on various types of 2D PSCs. We also discuss the crystal/natural quantum well (QW) structure and the original stability for 2D PSCs in detail. Finally, remaining challenges and outlooks are presented. 2. Crystal and Natural Quantum Well Structure The material structure has a substantial impact on performance. [49-51] Properties of 2D and 3D perovskites differ 2D perovskites demonstrate higher moisture stability, oxygen content, thermal stability, and a significantly lower ion migration/phase transition occurrence in comparison to 3D perovskite. These advantages imply huge potential for 2D perovskite in commercial applications in the photovoltaic field. However, the horizontal arrangement of the organic layer severely hinders the transport of carriers, and thus, the power conversion efficiency of 2D perovskite solar cells (PSCs) is significantly lower than that of 3D. Controlling the crystallization orientation to achieve rapid carrier transport can effe...

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“…[231] Initial results show good progress over interfacial charge transfer dynamics through, for example, simple fluorination of the aromatic spacers that can reduce the VB by 0.5 eV. [232][233][234] The use of the fluorinated cation FEA was shown to result in an enhanced interfacial hole extraction and suppression of undesired phases that contribute to PCEs over 22%. [115]…”

Section: Energy Level Engineeringmentioning

confidence: 99%

Layered Perovskites in Solar Cells: Structure, Optoelectronic Properties, and Device Design

Sirbu

Balogun

Milot

et al. 2021

Advanced Energy Materials

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optoelectronic properties akin to industrial juggernauts gallium arsenide and silicon. [1,2] Yet, the materials are compatible with solution-processing techniques such as inkjet printing and spray coating. [3] This unprecedented combination has led to the development of solar cells which already show power conversion efficiencies of over 25%, similar to state-of-the-art poly-Si and other thin-film technologies, in just over 10 years of development. [4] Hybrid perovskites are particularly interesting for indoor applications, with impressive efficiencies of over 35% demonstrated under indoor illumination which may prove a viable option to power the ever expanding Internet of Things. [5] Rather than competing with the current technology giants, perovskites can work together with other solar cell technologies in a tandem configuration. Record efficiencies of over 29% for silicon-perovskite tandem solar cells have already been reported and further progress is expected in the near future. [6] Although perovskite solar cells (PSCs) are on the verge of mass production, two main challenges remain: stability [7] and toxicity. [8] Multiple reviews already address the toxicity concern, and it will not be discussed here. [9][10][11] Layered hybrid perovskites (LPKs) have emerged as an answer to battle stability concerns. Although known for decades, LPKs have only recently been incorporated in photovoltaic (PV) applications, resulting in modest device power conversion efficiencies due to poorer optoelectronic properties. [12][13][14] However, their key advantage is the stabilizing effects of the organic interlayers, which prevents perovskite degradation. [15,16] The organic spacer inhibits ion migration which prevents the formation of irreversible degradation products. [17] Alternatively, LPKs can be deposited over the state-of-the-art perovskite materials to combine the high performance of 3D perovskites with the stabilizing properties of LPKs. [15] Here, the limiting factor is inefficient charge transport across the organic interlayer, currently preventing the full exploitation of the layered structure in PSCs.This can be approached in two ways, either by keeping the LPK layer very thin, currently the most popular approach, or by increasing the electrical conductivity of the material. [18,19] The conductivity can be enhanced through increasing the number of inorganic layers n, but this comes at the price of reduced stability. [20][21][22] The better approach is to enhance the charge transport in LPKs through the molecular engineering of the organic Layered hybrid perovskites (LPKs) have emerged as a viable solution to address perovskite stability concerns and enable their implementation in wide-scale energy harvesting. Yet, although more stable, the performance of devices incorporating LPKs still lags behind that of state-of-the-art, multication perovskite materials. This is typically assigned to their poor charge transport, currently caused by the choice of cations used within the organic layer. On balance, a compromise bet...

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Alkali Cation Doping for Improving the Structural Stability of 2D Perovskite in 3D/2D PSCs

Cited by 74 publications

References 58 publications

Manipulation of Perovskite Crystallization Kinetics via Lewis Base Additives

Manipulation of Perovskite Crystallization Kinetics via Lewis Base Additives

Crystallization Kinetics in 2D Perovskite Solar Cells

Layered Perovskites in Solar Cells: Structure, Optoelectronic Properties, and Device Design

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