Secondary Grain Growth in Organic–Inorganic Perovskite Films with Ethylamine Hydrochloride Additives for Highly Efficient Solar Cells

Ji, Chao; Liang, Chunjun; Zhang, Huimin; Sun, Mengjie; Song, Qi; Sun, Fulin; Feng, Xiaona; Liu, Ning; Gong, Hongkang; Li, Dan; You, Fangtian; He, Zhengjie

doi:10.1021/acsami.9b23468

Cited by 26 publications

(28 citation statements)

References 39 publications

(64 reference statements)

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“…Additionally, a vast microstructure transformation was also enabled by the use of reduced-dimensionality perovskites or 2D/3D hybrid perovskites. [115,159,160] Figure 9c presents several kinds of molecules used to make 2D/3D hybrid perovskites. Among these, incorporating butylammonium iodide (BAI) into the caesiumformamidinium perovskite starting solution, the surface microstructure and crystal structures can vary when comparing the pristine 3D perovskite in Figure 9d, [148] with the formation of 2D/3D hybrid perovskites.…”

Section: Surface Catalyst For Microstructure Transformationmentioning

confidence: 99%

Recent Progress on Perovskite Surfaces and Interfaces in Optoelectronic Devices

et al. 2021

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conversion efficiencies (PCEs) of perovskite solar cells (PeSCs) have already surpassed 25%, [4] which is comparable to current industrial-grade mono-crystalline silicon solar cells. This fantastic efficiency combined with potentially low-cost fabrication makes them more attractive than the most efficient photovoltaic technologies. [5] Similarly, perovskite light-emitting diodes (PeLEDs) are shown to have an extraordinary performance with external quantum efficiencies (EQEs) exceeding 20% in devices made from the solution phase at low temperatures. [6][7][8] We associated these notable improvements on device performance with lessons learned from organic optoelectronics and other semiconductor devices. Typically, many empirical approaches learned from others such as structural optimization, [9] interface engineering, [10] defects passivation, [11] etc., have been considered optimizing the carrier injection/extraction and mitigating undesirable non-radiative recombination losses. [12][13][14][15][16] Nonetheless, there is plenty of room optimizing nonradiative recombination losses in the bulk and at the interfaces to reach the efficiency limits. [17,18] Historically, band misalignments and interfacial defects have been considered the predominant factors responsible for the undesirable recombination at the various interfaces in devices. [19][20][21] In light of band misalignment, the resulting nonradiative recombination losses at the perovskite interfaces cause a substantial reduction in open-circuit voltages (V oc ) of the PeSCs, [14] mainly because of charge extraction suppression. For example, an energy barrier height of >0.1 eV is sufficient to block the extraction of majority carriers and to block the minority carriers from entering the undesirable transport layer, resulting in efficiency losses. [22] The presence of a charge injection barrier is also known to impact the turn-on voltage and device efficiency of PeLEDs. [23] Moreover, the deep-level defect-assisted recombination provides an additional path for intrinsic loss of charge carriers. [24][25][26] However, the origin and distribution of deep-level defects, a kind of defect that are far away from the band edge and can trap charge carriers, are highly debated topics. To date, there are several experimental observations confirming that a considerable density of deep-level defects retains at the interfaces of both the single-crystal and polycrystalline devices, and some surface passivation strategies can considerably eliminate the defects on the surfaces. [27][28][29] Based on photoemission Surfaces and heterojunction interfaces, where defects and energy levels dictate charge-carrier dynamics in optoelectronic devices, are critical for unlocking the full potential of perovskite semiconductors. In this progress report, chemical structures of perovskite surfaces are discussed and basic physical rules for the band alignment are summarized at various perovskite interfaces. Common perovskite surfaces are typically decorated by various compositional and structur...

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Section: Surface Catalyst For Microstructure Transformationmentioning

confidence: 99%

Recent Progress on Perovskite Surfaces and Interfaces in Optoelectronic Devices

et al. 2021

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“…Previous calculations show that the surface energy of the (100) plane is the lowest in FA‐based perovskites. [ 23 ] Therefore, the crystal grains with the (100) plane parallel to the film surface grow preferentially during the annealing process. It is reported that the (100) surface has a lower defect density than the other planes in perovskite films.…”

Section: Resultsmentioning

confidence: 99%

Controlled Crystallization of CsRb‐Based Multi‐Cation Perovskite Using a Blended Sequential Process for High‐Performance Solar Cells

et al. 2021

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High‐quality perovskite films with low defect densities and high carrier‐diffusion lengths are essential for high‐performance perovskite devices. Herein, a modified two‐step sequential method is proposed, in which equal amounts of Cs+ and Rb+ ions (Cs+Rb+) are added to a PbI2 solution in the first step of perovskite deposition. The incorporation of Cs+Rb+ results in trace amounts of δ‐CsPbI3, leading to a reduction in the grain size in the PbI2 layer that facilitates better penetration of the organic salts in the second step of the precursor deposition. Meanwhile, the low density of the δ‐CsPbI3 crystals act as seeds to regulate the nucleation and growth of the perovskite crystals. A single‐layered columnar large‐grain perovskite film is obtained. The addition of Cs+Rb+ promotes crystal growth along the (100) orientation, which is beneficial for the reduction of surface defects. The incorporated Rb+ ions can regulate the remaining PbI2 in the perovskite. The improved quality of the perovskite film results in a significantly prolonged carrier lifetime of ≈7.01 μs and an enhanced electron diffusion length of ≈2.84 μm. As a result, the photovoltaic parameters are all improved in the established devices and a power conversion efficiency of 21.49% is reached.

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“…As the defects associated with grain boundaries may induce losses, their volumetric fraction should be low compared to that of the ordered grains. As a consequence, the grain size is a crucial parameter, not only with conventional semiconductors like Si [9][10][11], but also with a number of currently emerging materials, such as halide perovskites [12][13][14][15].…”

Section: Introductionmentioning

confidence: 99%

Relevance of processing parameters for grain growth of metal halide perovskites with nanoimprint

et al. 2021

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The quality and the stability of devices prepared from polycrystalline layers of organic–inorganic perovskites highly depend on the grain sizes prevailing. Tuning of the grain size is either done during layer preparation or in a post-processing step. Our investigation refers to thermal imprint as the post-processing step to induce grain growth in perovskite layers, offering the additional benefit of providing a flat surface for multi-layer devices. The material studied is MAPbBr3; we investigate grain growth at a pressure of 100 bar and temperatures of up to 150 °C, a temperature range where the pressurized stamp is beneficial to avoid thermal degradation. Grain coarsening develops in a self-similar way, featuring a log-normal grain size distribution; categories like ‘normal’ or ‘secondary’ growth are less applicable as the layers feature a preferential orientation already before imprint-induced grain growth. The experiments are simulated with a capillary-based growth law; the respective parameters are determined experimentally, with an activation energy of Q ≈ 0.3 eV. It turns out that with imprint as well the main parameter relevant to grain growth is temperature; to induce grain growth in MAPbBr3 within a reasonable processing time a temperature of 120 °C and beyond is advised. An analysis of the mechanical situation during imprint indicates a dominance of thermal stress. The minimization of elastic energy and surface energy together favours the development of grains with (100)-orientation in MaPbBr3 layers. Furthermore, the experiments indicate that the purity of the materials used for layer preparation is a major factor to achieve large grains; however, a diligent and always similar preparation of the layer is equally important as it defines the pureness of the resulting perovskite layer, intimately connected with its capability to grow. The results are not only of interest to assess the potential of a layer with respect to grain growth when specific temperatures and times are chosen; they also help to rate the long-term stability of a layer under temperature loading, e.g. during the operation of a device.

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Secondary Grain Growth in Organic–Inorganic Perovskite Films with Ethylamine Hydrochloride Additives for Highly Efficient Solar Cells

Cited by 26 publications

References 39 publications

Recent Progress on Perovskite Surfaces and Interfaces in Optoelectronic Devices

Recent Progress on Perovskite Surfaces and Interfaces in Optoelectronic Devices

Controlled Crystallization of CsRb‐Based Multi‐Cation Perovskite Using a Blended Sequential Process for High‐Performance Solar Cells

Relevance of processing parameters for grain growth of metal halide perovskites with nanoimprint

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