Azide additive acting as a powerful locker for Li+ and TBP in spiro-OMeTAD toward highly efficient and stable perovskite solar cells

Han, Yipeng; Zhang, Guang; Xie, Haibing; Kong, Tengfei; Li, Yahong; Zhang, Yang; Song, Jing; Bi, Dongqin

doi:10.1016/j.nanoen.2022.107072

Cited by 37 publications

(34 citation statements)

References 34 publications

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“…The SEM and EDS were characterized to study the effect of [Bmim] + [DBP] − IL modification on the top and cross-sectional morphologies of perovskite and Spiro-OMeTAD. As shown in Figure 1c,d The shifted XPS peak indicates the interaction between IL and Pb 2+ , [32] which is helpful for passivating the uncoordinated Pb 2+ defects. As shown in Figure S3, Supporting Information, the SCLC characterization is used to investigate the effects of IL modification on the trap state density of perovskite films based on the device structure of ITO/PEDOT-PSS/Perovskite/ IL/Spiro-OMeTAD/Ag.…”

Section: Resultsmentioning

confidence: 93%

Phosphate Functionalized Ionic Liquid: An Efficient Li⁺ Migration Inhibitor and Hole Extraction Accelerator for Perovskite Solar Cells

Hou

Kang

et al. 2022

Adv Materials Inter

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There is no doubt that the hole transporting layer (HTL) plays an indispensable role in highly efficient devices. [5] The materials used for HTL include: (1) organic polymer molecules, [6,7] such as poly(3,4ethylenedioxy thiophene):poly(styrene sulfonate) (PEDOT:PSS), poly[bis(4-phenyl) (2,4,6-trimethylphenyl)amine] (PTAA) and poly(3-hexylthiophen-2,5-diyl) (P3HT); (2) inorganic compound, [8] for instance, CuSCN and NiO X . Besides, small molecule HTL materials have been widely studied due to their designability in molecular structure. [9] The organic 2,2′,7,7′-tetrakis (N,N-dip-methoxyphenylamine)-9,9′spirobifluorene (Spiro-OMeTAD) has been extensively employed as hole transport layer for high-performance devices due to its suitable energy level alignment and great solubility. [10] However, the amorphous characteristic of Spiro-OMeTAD depends its low hole mobility (∼4 × 10 −5 cm 2 V −1 s −1 ). [10,11] The bis(trifluoromethane)sulfonimide lithium salt (Li-TFSI) and 4-tert-Butylpyridine (TBP) are always used as the dopant of Spiro-OMeTAD. [10,11] TBP was used to reduce phase separation of Spiro-OMeTAD and Li-TFSI. [10,11] Li-TFSI can enhance the hole mobility of Spiro-OMeTAD by promoting the oxidation process of Spiro-OMeTAD in an ambient atmosphere. [12] However, this oxidation process is always uncontrollable owing to the oxidized Spiro-OMeTAD can be reduced to its initial state during the device operation process, [13] which leads to the instable device. Besides, the hygroscopic properties Lithium bis(trifluoromethanesulfonyl)imide (Li-TFSI) doped 2,2′,7,7′ -tetrakis(N,N-di-p-methoxyphenylamine)-9,9′-spirobifluorene (Spiro-OMeTAD) is employed as one of the most common hole transport layer. However, the Li + in Li-TFSI is easy to migrate from Spiro-OMeTAD to perovskite and SnO 2 , left the voids/pinholes in perovskite film to accelerate the invasion of oxygen and moisture, and lead to the device degradation. Here, the 1-butyl-3-methyl imidazolium phosphate dibutyl ester ([Bmim] + [DBP] − ) ionic liquid (IL) is prepared and used to modify the perovskite/Spiro-OMeTAD interface in the perovskite solar cells. The coordination interaction between P  O in [Bmim] + [DBP] − IL and Pb 2+ can improve the morphology of perovskite film by passivating the uncoordinated Pb 2+ defects. The interaction between P  O and Li + can suppress the undesired Li + migration. The regulated energy level assignment and ion nature of [Bmim] + [DBP] − IL can accelerate the carrier extraction at perovskite/Spiro-OMeTAD interface. The device based on the [Bmim] + [DBP] − IL interface modification yields a highly efficient photoelectric conversion efficiency of 21.16% and improved stability, outperforming that of control (19.31%) devices under the illumination of 100 mW cm −2 (AM 1.5 G).

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Section: Resultsmentioning

confidence: 93%

Phosphate Functionalized Ionic Liquid: An Efficient Li⁺ Migration Inhibitor and Hole Extraction Accelerator for Perovskite Solar Cells

Hou

Kang

et al. 2022

Adv Materials Inter

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“…These observations imply that RbI and TBP interact with each other and form a complexation. As shown in Figure S3, the samples were examined by Fourier transform infrared spectroscopy (FTIR) to investigate the formation of the RbI/TBP complex, we noted that the asymmetric vibrational mode of the C–C bond at 1120 cm –1 in the complex sample is not the same as the original one, and the pyridine ring vibration originally shown at 1596 cm –1 is shifted to a higher wavenumber of 1598 cm –1 for the RbI/TBP complex, , indicating the interaction between RbI and TBP in HTL. Figure f shows the effect of RbI on preventing Li-TFSI aggregation, the rapid evaporation of TBP in the original film leads to the aggregation of Li-TFSI, and water molecules penetrate rapidly into the perovskite film from the resulting pinholes and voids, while the complex formed by RbI and TBP inhibits the evaporation of TBP, resulting in a uniform distribution of spiro-OMeTAD with dense and pinhole-free films.…”

Section: Resultsmentioning

confidence: 99%

Rubidium Iodide-Doped Spiro-OMeTAD as a Hole-Transporting Material for Efficient Perovskite Photodetectors

Zhang

Wang

et al. 2022

J. Phys. Chem. C

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2,2′,7,7′-Tetrakis-(N,N-di-p-methoxyphenyl-amine)-9,9′-spirobifluorene (spiro-OMeTAD) is one of the broadly used hole transport materials for high-performance perovskite photodetectors. However, to achieve high hole mobility and conductivity, it often requires the addition of additives and dopants with hygroscopic properties similar to bis(trifluoromethane)sulfonamide lithium salt (Li-TFSI) and 4-tert-butylpyridine (TBP), which are forced to undergo aggregation and hydrolysis under environmental conditions, hence leading to pinholes/voids in resultant films. In this work, we added rubidium iodide (RbI) to spiro-OMeTAD together with Li-TFSI and TBP, and the complexation between RbI and TBP prevented the evaporation of TBP that hinders the aggregation of Li-TFSI and reduces the undesired voids. Consequently, RbI-doped spiro-OMeTAD serves as the hole transport layer (HTL) for perovskite photodetectors, enhancing the conductivity and hole transport abilities of the hole transport layer, which also helps to promote energy-level matching with the perovskite layer. The performance of the perovskite photodetector is verified by analyzing the current density–voltage characteristics as well as the transient and dynamic photocurrent response characteristics. Devices with RbI-doped HTLs exhibit a champion specific detectivity approaching 3.77 × 1013 Jones and a linear dynamic range of 114 dB. This work provides a feasible approach to improve the stability of small-molecule-based hole transport materials for perovskite photodetectors.

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“…[77,84] In addition, spiro derivatives that own a high conductivity, well-matched energy band alignment with perovskite, and inherent water-resistant properties have also brought about exciting results thanks to great advances in molecular engineering. [124,107] Newly-developed functional materials that integrate not only charge extraction ability but also encapsulating property, as well as defect passivation, are highly desired to simultaneously improve photovoltaic performance and device stability. [125,126] The long-term stability of PSCs remains a great challenge for commercial application in the future, [127][128][129][130][131] especially when operated in harsh conditions with a high temperature, high humidity, and exposure under solar illumination with high-energy UV photons.…”

Section: Discussionmentioning

confidence: 99%

“…Moreover, the modification in HTL retarded the penetration of extrinsic elements such as O 2 , H 2 O, and Ag by constructing a strengthened barrier against mass diffusion. [106][107][108][109][110][111][112][113] 3.6. Small Molecules in the Bulk and at the Interface Except for the functional layers themselves, the interfaces that bridge each functional layer in PSCs can affect the efficiency and stability of the device to a large extent.…”

Section: Hydrophobic Polymer Additivesmentioning

confidence: 99%

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Spiro‐OMeTAD‐Based Hole Transport Layer Engineering toward Stable Perovskite Solar Cells

Shen

Deng

2022

Small Methods

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Perovskite solar cells (PSCs) have undergone unprecedented growth in the past decade as an emerging photovoltaic technology. Up till now, the power conversion efficiency of PSCs has exceeded 25% that rivals silicon solar cells and there is still room for further enhancement. However, the development in long‐term stability lags far behind, which remains a great concern for the commercial application in the future. The device instability mainly arises from the functional components, including perovskite film, charge transport layers, and electrodes along with the involved interfaces. As the most widely studied hole transport layer at the current stage, 2,2′,7,7′‐tetrakis(N,N‐di(4‐methoxyphenyl)amino)‐9,9‐spirobifluorene (Spiro‐OMeTAD) helps contribute to the achievement of record efficiency but it weakens the device stability due to the doping‐induced side effects such as hygroscopicity and ion migration. Great efforts are devoted to boosting the stability of Spiro‐OMeTAD while maintaining excellent photovoltaic performance. In this review, the fundamental properties of Spiro‐OMeTAD have been summarized and the recent advances in engineering Spiro‐OMeTAD‐based hole transport layer for the sake of highly efficient PSCs with enhanced longevity are highlighted. In the end, an outlook for the further optimization of Spiro‐OMeTAD is provided and the issues related to large‐scale production are discussed.

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Azide additive acting as a powerful locker for Li+ and TBP in spiro-OMeTAD toward highly efficient and stable perovskite solar cells

Cited by 37 publications

References 34 publications

Phosphate Functionalized Ionic Liquid: An Efficient Li⁺ Migration Inhibitor and Hole Extraction Accelerator for Perovskite Solar Cells

Phosphate Functionalized Ionic Liquid: An Efficient Li⁺ Migration Inhibitor and Hole Extraction Accelerator for Perovskite Solar Cells

Rubidium Iodide-Doped Spiro-OMeTAD as a Hole-Transporting Material for Efficient Perovskite Photodetectors

Spiro‐OMeTAD‐Based Hole Transport Layer Engineering toward Stable Perovskite Solar Cells

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Azide additive acting as a powerful locker for Li+ and TBP in spiro-OMeTAD toward highly efficient and stable perovskite solar cells

Cited by 37 publications

References 34 publications

Phosphate Functionalized Ionic Liquid: An Efficient Li+ Migration Inhibitor and Hole Extraction Accelerator for Perovskite Solar Cells

Phosphate Functionalized Ionic Liquid: An Efficient Li+ Migration Inhibitor and Hole Extraction Accelerator for Perovskite Solar Cells

Rubidium Iodide-Doped Spiro-OMeTAD as a Hole-Transporting Material for Efficient Perovskite Photodetectors

Spiro‐OMeTAD‐Based Hole Transport Layer Engineering toward Stable Perovskite Solar Cells

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Product

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Phosphate Functionalized Ionic Liquid: An Efficient Li⁺ Migration Inhibitor and Hole Extraction Accelerator for Perovskite Solar Cells

Phosphate Functionalized Ionic Liquid: An Efficient Li⁺ Migration Inhibitor and Hole Extraction Accelerator for Perovskite Solar Cells