Enhanced Charge Transport by Incorporating Formamidinium and Cesium Cations into Two‐Dimensional Perovskite Solar Cells

Gao, Liguo; Wang, Shirong; Chen, Xihan; Xiao, Chuanxiao; Larson, Bryon W.; Dunfield, Sean P.; Berry, Joseph J.; Zhu, Kai

doi:10.1002/anie.201905690

Cited by 74 publications

(50 citation statements)

References 43 publications

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“…Inspired by cation engineering in 3D perovskite, through the double doping or triple doping of A-site ions, the decomposition energy of perovskite can be improved, thereby improving stability (as shown in Figure 6a). [115][116][117] The A-site ion doping can also induce the preferred orientation of 2D perovskite during the fabrication process. However, it is a key point to understand the relationship between the crystal microstructure and crystallization kinetics, which is related to the carrier transport of 2D perovskite materials.…”

Section: Ion Composition Of Precursormentioning

confidence: 99%

Crystallization Kinetics in 2D Perovskite Solar Cells

Wang

Lei

et al. 2020

Advanced Energy Materials

141

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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Section: Ion Composition Of Precursormentioning

confidence: 99%

Crystallization Kinetics in 2D Perovskite Solar Cells

Wang

Lei

et al. 2020

Advanced Energy Materials

141

124

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“…[ 15 ] The obtained J sc , while is among the top values based on low n ‐value quasi‐2D PSCs ( n ≤ 5), still lags behind that of 3D PSCs (e.g., values exceeding 24 mA cm −2 have been realized [ 16,17 ] ). Since the issue of low J sc is primarily associated with the poor charge transport in quasi‐2D perovskites, [ 18–20 ] the development of rationally controlling quasi‐2D perovskite growth with better‐aligned phase distribution and preferred crystal orientation holds great promise to overcome this issue. [ 21–24 ]…”

Section: Figurementioning

confidence: 99%

Water‐Assisted Crystal Growth in Quasi‐2D Perovskites with Enhanced Charge Transport and Photovoltaic Performance

Wang

et al. 2020

Advanced Energy Materials

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Perovskite solar cells (PSCs) employing 3D organic-inorganic hybrid perovskite photoabsorbers have received tremendous progress with state-of-the-art power conversion efficiency (PCE) exceeding 25% during the last a dozen years. [1] However, ambient instability of 3D perovskite materials remains a critical obstacle for realistic applications of PSCs. [2,3] A strategy in addressing the poor stability is to reduce the structural dimensionality of perovskites via the introduction of long-chain organic ligands by forming Ruddlesden-Popper (RP) quasi-2D perovskites. [4,5] The organic ligands are bound to the 3D inorganic framework via coulombic interactions, resulting in a layered structure. The general formula of RP-2D perovskites takes the form of (L) 2 A n−1 Pb n I 3n+1 (n = 1, 2, 3, 4…) where A is the methylammonium (MA +), formamidinium (FA +), or cesium (Cs +) cations, L is the bulky organic ligands, e.g., butylammonium (BA +) or 2-phenylethylammonium (PEA +), and n is the number of layers in the [PbI 6 ] 4− octahedral sheets. [4-7] The incorporation of hydrophobic bulky organic ligands can not only enhance the stability of perovskites with minimized permeation of water molecules but also increase the formation energy of perovskites to mitigate thermal degradation and ion migration. [8-10] These merits alongside the quantum confinement have rendered quasi-2D perovskites great potentials for optoelectronic applications with a wide tunability on the bandgap or photophysical properties. [7] Unfavorably, quasi-2D perovskites are generally associated with a large exciton binding energy (hundreds of meV) due to the insulating nature of bulky organic ligands and the specific layered arrangement. [11,12] As a result, charge transport and extraction are hindered in quasi-2D PSCs. To date, the highest reported PCEs of quasi-2D PSCs (n ≤ 5) remain around 18%, [13-15] showing considerable performance gaps with regard to 3D-PSCs. The PCE (η) of photovoltaic cells is determined by the general relation, J V P FF sc oc light η = × × (V oc is the open-circuit voltage, FF is the fill factor, and P light is the illumination intensity). In quasi-2D PSCs, the relatively low J sc is more restrictive for Organic-inorganic hybrid quasi-2D perovskites have shown excellent stability for perovskite solar cells (PSCs), while the poor charge transport in quasi-2D perovskites significantly undermines their power conversion efficiency (PCE). Here, studies on water-controlled crystal growth of quasi-2D perovskites are presented to achieve high-efficiency solar cells. It is demonstrated that the (BA) 2 MA 4 Pb 5 I 16-based PSCs (n = 5) processed with water-containing precursors display an increased short-circuit current density (J sc) of 19.01 mA cm −2 and PCE over 15%. The enhanced performance is attributed to synergetic growths of the 3D and 2D phase components aided by the formed hydration (MAI•H 2 O), leading to modulations on the crystal orientation and phase distribution of various n-value components, which facilitate interphase charge tr...

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Section: Strategies To Fabricate High‐quality Rp Perovskite Film In Pscsmentioning

confidence: 99%

“…Benefitting from these merits, the PCE of RP perovskite‐based PSC with triple cations improved from 7.80% to 14.23% with an enhancement ratio of 80% compared with RP perovskite‐based PSCs with single cation. [ 140 ] For the BA 2 MA 3 Pb 4 I 13 perovskite film, the incorporation of FA + and Cs + also greatly improved film quality with increased grain size, reduced cracks, and lowered trap states, contributing to a PCE of 15.58% in PSCs with an obviously enhanced thermal stability. [ 141 ]…”

Section: Strategies To Fabricate High‐quality Rp Perovskite Film In Pscsmentioning

confidence: 99%

High‐Quality Ruddlesden–Popper Perovskite Film Formation for High‐Performance Perovskite Solar Cells

et al. 2021

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In the last decade, perovskite solar cells (PSCs) have undergone unprecedented rapid development and become a promising candidate for a new‐generation solar cell. Among various PSCs, typical 3D halide perovskite‐based PSCs deliver the highest efficiency but they suffer from severe instability, which restricts their practical applications. By contrast, the low‐dimensional Ruddlesden–Popper (RP) perovskite‐based PSCs have recently raised increasing attention due to their superior stability. Yet, the efficiency of RP perovskite‐based PSCs is still far from that of the 3D counterparts owing to the difficulty in fabricating high‐quality RP perovskite films. In pursuit of high‐efficiency RP perovskite‐based PSCs, it is critical to manipulate the film formation process to prepare high‐quality RP perovskite films. This review aims to provide comprehensive understanding of the high‐quality RP‐type perovskite film formation by investigating the influential factors. On this basis, several strategies to improve the RP perovskite film quality are proposed via summarizing the recent progress and efforts on the preparation of high‐quality RP perovskite film. This review will provide useful guidelines for a better understanding of the crystallization and phase kinetics during RP perovskite film formation process and the design and development of high‐performance RP perovskite‐based PSCs, promoting the commercialization of PSC technology.

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Enhanced Charge Transport by Incorporating Formamidinium and Cesium Cations into Two‐Dimensional Perovskite Solar Cells

Cited by 74 publications

References 43 publications

Crystallization Kinetics in 2D Perovskite Solar Cells

Crystallization Kinetics in 2D Perovskite Solar Cells

Water‐Assisted Crystal Growth in Quasi‐2D Perovskites with Enhanced Charge Transport and Photovoltaic Performance

High‐Quality Ruddlesden–Popper Perovskite Film Formation for High‐Performance Perovskite Solar Cells

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