Uniform Permutation of Quasi-2D Perovskites by Vacuum Poling for Efficient, High-Fill-Factor Solar Cells

Zhang, Jia; Qin, Jiajun; Wang, Miaosheng; Bai, Yujie; Han, Zixuan; Keum, Jong K.; Tao, Runming; Xu, Hengxing; Yu, Haomiao; Haacke, Stefan; Hu, Bin

doi:10.1016/j.joule.2019.09.020

Cited by 183 publications

(202 citation statements)

References 37 publications

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“…This narrow‐graded dispersion with suppressed lower‐ n phases strongly indicates an efficient energy transfer with decreased transport time. [ 26,39 ]…”

Section: Resultsmentioning

confidence: 99%

Coordination Engineering of Single‐Crystal Precursor for Phase Control in Ruddlesden–Popper Perovskite Solar Cells

Qin

Zhong

Intemann

et al. 2020

Advanced Energy Materials

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efficiencies (PCE). [1,2] However, the intrinsic instability of 3D perovskite materials still remains unresolved. [3,4] Inert bulky organic cations can not only enhance their structural stability via strong interactions between covering organic cations and the [PbI 6 ] − units, but also block moisture from penetrating and corroding inner inorganic layers. [5,6] By incorporation of a larger cation into the 3D structure, the most common type is the (100)-oriented cutting direction, forming representative Ruddlesden-Popper perovskite (RPP) with a chemical formula (A′) 2 (A) n−1 Pb n I 3n+1 (A′ is a primary monovalent cations). [7,8] Unfortunately, the confinement effects of organic spacers also lead to a strong quantum and dielectric confinement in 2D perovskite. Moreover, the decreased conductivity of the organic layers prevents the carrier charge transport between perovskite quantum wells. [9] Thus, RPP exhibits a wider bandgap, a higher exciton binding energy (E b ), and lower charge mobility relative to the 3D perovskites, which results in poor efficiencies. Note that a weak quantum confinement would arise from an increase thickness of layers (n value), leading to a remarkable decrease in the optical bandgap, making it highly desirable to increase the number (n ≥ 4) of inorganic sheets between two adjacent organic spacers by forming quasi-2D structures. [10,11] In addition, through rational design 2D Ruddlesden-Popper perovskites (RPPs) have recently drawn significant attention because of their structural variability that can be used to tailor optoelectronic properties and improve the stability of derived photovoltaic devices. However, charge separation and transport in 2D perovskite solar cells (PSCs) suffer from quantum well barriers formed during the processing of perovskites. It is extremely difficult to manage phase distributions in 2D perovskites made from the stoichiometric mixtures of precursor solutions. Herein, a generally applicable guideline is demonstrated for precisely controlling phase purity and arrangement in RPP films. By visually presenting the critical colloidal formation of the single-crystal precursor solution, coordination engineering is conducted with a rationally selected cosolvent to tune the colloidal properties. In nonpolar cosolvent media, the derived colloidal template enables RPP crystals to preferentially grow along the vertically ordered alignment with a narrow phase variation around a target value, resulting in efficient charge transport and extraction. As a result, a recordhigh power conversion efficiency (PCE) of 14.68% is demonstrated for a (TEA) 2 (MA) 2 Pb 3 I 10 (n = 3) photovoltaic device with negligible hysteresis. Remarkably, superior stability is achieved with 93% retainment of the initial efficiency after 500 h of unencapsulated operation in ambient air conditions.

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“…This narrow‐graded dispersion with suppressed lower‐ n phases strongly indicates an efficient energy transfer with decreased transport time. [ 26,39 ]…”

Section: Resultsmentioning

confidence: 99%

Coordination Engineering of Single‐Crystal Precursor for Phase Control in Ruddlesden–Popper Perovskite Solar Cells

Qin

Zhong

Intemann

et al. 2020

Advanced Energy Materials

View full text Add to dashboard Cite

show abstract

“…[ 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.…”

Section: Figurementioning

confidence: 99%

“…Recently, a PCE of 18.04% with a J sc of 17.91 mA cm −2 was achieved in (PEA) 2 MA 4 Pb 5 I 16 quasi‐2D PSCs based on vacuum poling method. [ 14 ] Compared to the impressive FF (82.4%) and V oc (1.22 V), the J sc is less satisfactory, becoming a limiting parameter for the PCE. By using a new bulky organic ligand 2‐(methylthio)ethylamine hydrochloride (MTEACl), Huang and co‐workers reported quasi‐2D (MTEA) 2 MA 4 Pb 5 I 16 PSCs with the PCE of 18.06% and J sc of 21.77 mA cm −2 .…”

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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“…Recently, Qing and co‐workers found adding DMSO into the DMF solvent system can greatly improve the crystallinity and device performance . Other technique such as vacuum poling was also proved to be beneficial to the crystallization . These results demonstrated that by controlling gel stage, it is possible to improve crystallinity.…”

Section: Resultsmentioning

confidence: 96%

Cation Diffusion Guides Hybrid Halide Perovskite Crystallization during the Gel Stage

et al. 2020

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Lead halide perovskites with mixed cations/anions often suffer from phase segregation, which is detrimental to device efficiency and their long‐term stability. During perovskite film growth, the gel stage (in between liquid and crystalline) correlates to phase segregation, which has been rarely explored. Herein, cation diffusion kinetics are systematically investigated at the gel stage to develop a diffusion model obeying Fick's second law. Taking 2D layered perovskite as an example, theoretical and experimental results reveal the impact of diffusion coefficient, temperature, and gel duration on the film growth and phase formation. A homogenous 2D perovskite thin film was then fabricated without significant phase segregation. This in‐depth understanding of gel stage and relevant cation diffusion kinetics would further guide the design and processing of halide perovskites with mixed composition to meet requirements for optoelectronic applications.

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Uniform Permutation of Quasi-2D Perovskites by Vacuum Poling for Efficient, High-Fill-Factor Solar Cells

Cited by 183 publications

References 37 publications

Coordination Engineering of Single‐Crystal Precursor for Phase Control in Ruddlesden–Popper Perovskite Solar Cells

Coordination Engineering of Single‐Crystal Precursor for Phase Control in Ruddlesden–Popper Perovskite Solar Cells

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

Cation Diffusion Guides Hybrid Halide Perovskite Crystallization during the Gel Stage

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