Synergetic effects of electrochemical oxidation of Spiro-OMeTAD and Li<sup>+</sup> ion migration for improving the performance of n–i–p type perovskite solar cells

Ding, Changzeng; Huang, Rong; Ahläng, Christian; Lin, Jian; Zhang, Liangping; Zhang, Dongyu; Luo, Qun; Li, Fangsen; Österbacka, Ronald; Ma, Chang‐Qi

doi:10.1039/d0ta12458c

Cited by 65 publications

(71 citation statements)

References 47 publications

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“…In this work, both pre‐ and post‐oxidation of the Spiro‐OMeTAD layers were performed to improve the conductivity of the Spiro‐OMeTAD layer and the consequent solar cell performance. [ 50 ] Although these cells were oxidized in air under similar conditions, the variation of device performance indicated that oxidization degree of the Spiro‐OMeTAD films was not well controlled and the properties of Spiro‐OMeTAD varied from batch to batch. In other words, the conductivity as well as the surface property of the Spiro‐OMeTAD layer is different from each other after oxidation, which influences the silver electrode on it and leads to a large variation of the failure time during aging (Table S1, Figure S1, Supporting Information).…”

Section: Resultsmentioning

confidence: 99%

Revealing the Mechanism behind the Catastrophic Failure of n‐i‐p Type Perovskite Solar Cells under Operating Conditions and How to Suppress It

Ding

Yin

Zhang

et al. 2021

Adv Funct Materials

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The n‐i‐p type perovskite solar cells suffer unpredictable catastrophic failure under operation, which is a barrier for their commercialization. The fluorescence enhancement at Ag electrode edge and performance recovery after cutting the Ag electrode edge off prove that the shunting position is mainly located at the edge of device. Surface morphology and elemental analyses prove the corrosion of the Ag electrode and the diffusion of Ag+ ions on the edge for aged cells. Moreover, much condensed and larger Ag clusters are formed on the MoO3 layer. Such a contrast is also observed while comparing the central and the edge of the Ag/Spiro‐OMeTAD film. Hence, the catastrophic failure mechanism can be concluded as photon‐induced decomposition of the perovskite film and release reactive iodide species, which diffuse and react with the loose Ag clusters on the edge of the cell. The corrosion of the Ag electrode and the migration of Ag+ ions into Spiro‐OMeTAD and perovskite films lead to the forming of conducting filament that shunts the cell. The more condensed Ag cluster on the MoO3 surface as well as the blocking of holes within the Spiro‐OMeTAD/MoO3 interface successfully prevent the oxidation of Ag electrode and suppress the catastrophic failure.

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Section: Resultsmentioning

confidence: 99%

Revealing the Mechanism behind the Catastrophic Failure of n‐i‐p Type Perovskite Solar Cells under Operating Conditions and How to Suppress It

Ding

Yin

Zhang

et al. 2021

Adv Funct Materials

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“…The same trend of Li + ion distribution had been reported in previous literature. 44,45 For the control device, a much higher Li + ion signal at the SnO 2 layer than that at the HTL can be found, suggesting a rather serious Li + ion migration. In sharp contrast, Li + ions primarily located within the target HTL and a relatively small portion of Li + ions are diffused out and detected at the SnO 2 layer, indicating the ion migration has been greatly suppressed.…”

Section: Resultsmentioning

confidence: 99%

Crowning lithium ions in hole transport layer toward stable perovskite solar cells

Shen¹,

Deng²,

Chen³

et al. 2021

Preprint

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State-of-art perovskite solar cells exhibit comparable power conversion efficiency to silicon photovoltaics. However, the device stability remains a major obstacle that restricts widespread application. Doping hole transport layer induced hygroscopicity, ion diffusion, and use of polar solvent are detrimental factors for performance degradation of perovskite solar cells. Here, we report phase transfer catalyzed LiTFSI doping in Spiro-OMeTAD to address these negative impacts. 12-crown-4 as an efficient phase transfer catalyst promotes the dissolution of LiTFSI without requiring acetonitrile. Crowning Li+ ions by forming more stable and less diffusive crown ether-Li+ complexes retards the generation of hygroscopic lithium oxides and mitigates Li+ ion migration. Optimized solar cells deliver enhanced power conversion efficiency and significantly improved stability under humid and thermal conditions compared with the control device. This method can also be applied to dope π-conjugated polymer. Our findings provide a facile avenue to improve the long-term stability of perovskite solar cells.

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“…The same trend of Li + ‐ion distribution had been reported in previous reports in the literature. [ 46,47 ] For the control device, a much higher Li + ‐ion signal at the SnO 2 layer than that at the HTL can be found, suggesting a rather serious Li + ‐ion migration. In sharp contrast, Li + ions primarily located within the target HTL and a relatively small portion of Li + ions are diffused out and detected at the SnO 2 layer, indicating the ion migration has been greatly suppressed.…”

Section: Resultsmentioning

confidence: 99%

Crowning Lithium Ions in Hole‐Transport Layer toward Stable Perovskite Solar Cells

et al. 2022

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arises from the indispensable dopants. On the one hand, the metal halide perovskite film is vulnerable to polar solvent and it is desired to avoid or reduce the use of acetonitrile. [10] On the other hand, the hygroscopic lithium salt facilitates moisture penetration and Li + -ion migration that is accelerated under high temperature conditions induces lithium intercalation into the perovskite layer with the formation of deleterious defects. [11] Thus far, considerable efforts have been devoted to optimizing the HTL of PSCs for enhanced PCE and stability. [12][13][14] The research community is actively searching for equivalent substitutes [15][16][17][18] to Spiro-OMeTAD for simple synthesis and cost reduction. Notwithstanding the recent success, LiTFSI is essential to these newly synthesized HTLs and Spiro-OMeTAD still represents the best choice for PSCs at the current stage owing to its high compatibility with dopants and energy band matching with perovskite. [19][20][21] Toward Spiro-OMeTAD-based HTL, alternative dopants instead of LiTFSI such as Spiro(TFSI) 2 , [22] lithium-ion endohedral fullerene, [23] and lithium-ion-free salts [24,25] have been studied to eliminate the notorious effect of Li + ions. These advances bring the benefit of enhanced device stability but there is still room for improvement in the PCE. The progress in boosting the long-term stability of PSCs lags far behind the rapid increase in PCE. Therefore, it is an urgent need to minimize the negative effects of dopants while maintaining device performance not only for Spiro-OMeTAD but also for other candidate HTLs. Developing a simple yet efficient method to solve these problems is expected but now it remains challenging.Here, we demonstrate a phase-transfer catalyzed method for LiTFSI doping in Spiro-OMeTAD to improve the stability of PSCs. Crown ether is a class of ligands that can bind various cations depending on the cavity diameter and the target ion size. 12-crown-4, a typical representative of crown ether family, is added into the Spiro-OMeTAD precursor to replace the acetonitrile. The modified composition in Spiro-OMeTAD precursor solution is superior to the conventional recipe in following aspects. First, 12-crown-4 as a lithium ionophore can selectively bond with Li + ions through hostguest interaction and promote the dissolution of LiTFSI in CB without requiring acetonitrile. The introduction of the Li(12-crown-4) + complexes can also passivate the defects and reduce the charge recombination in the perovskite film both State-of-the-art perovskite solar cells (PSCs) exhibit comparable power conversion efficiency (PCE) to that of silicon photovoltaic devices. However, the device stability remains a major obstacle that restricts widespread application. Doping-induced hygroscopicity, ion diffusion, and use of polar solvents in the hole-transport layer are detrimental factors for performance degradation of PSCs. Here, phase-transfer-catalyzed LiTFSI doping in Spiro-OMeTAD is developed to address these negative impacts. 12-Crown-4 as an...

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Synergetic effects of electrochemical oxidation of Spiro-OMeTAD and Li⁺ ion migration for improving the performance of n–i–p type perovskite solar cells

Abstract: n-i-p Type perovskite solar cell generally requires air oxidation of Spiro-OMeTAD layer to achieve high power conversion efficiency (PCE). However, the detailed oxidation mechanism is still not fully understood. In...

Cited by 65 publications

References 47 publications

Revealing the Mechanism behind the Catastrophic Failure of n‐i‐p Type Perovskite Solar Cells under Operating Conditions and How to Suppress It

Revealing the Mechanism behind the Catastrophic Failure of n‐i‐p Type Perovskite Solar Cells under Operating Conditions and How to Suppress It

Crowning lithium ions in hole transport layer toward stable perovskite solar cells

Crowning Lithium Ions in Hole‐Transport Layer toward Stable Perovskite Solar Cells

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Synergetic effects of electrochemical oxidation of Spiro-OMeTAD and Li+ ion migration for improving the performance of n–i–p type perovskite solar cells

Abstract: n-i-p Type perovskite solar cell generally requires air oxidation of Spiro-OMeTAD layer to achieve high power conversion efficiency (PCE). However, the detailed oxidation mechanism is still not fully understood. In...

Cited by 65 publications

References 47 publications

Revealing the Mechanism behind the Catastrophic Failure of n‐i‐p Type Perovskite Solar Cells under Operating Conditions and How to Suppress It

Revealing the Mechanism behind the Catastrophic Failure of n‐i‐p Type Perovskite Solar Cells under Operating Conditions and How to Suppress It

Crowning lithium ions in hole transport layer toward stable perovskite solar cells

Crowning Lithium Ions in Hole‐Transport Layer toward Stable Perovskite Solar Cells

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Synergetic effects of electrochemical oxidation of Spiro-OMeTAD and Li⁺ ion migration for improving the performance of n–i–p type perovskite solar cells