Dual Functional Doping of KMnO<sub>4</sub> in Spiro-OMeTAD for Highly Effective Planar Perovskite Solar Cells

Yang, Yuqian; Wu, Jihuai; Liu, Xuping; Guo, Qiyao; Wang, Xiaobing; Liu, Lin; Ding, Yong; Lin, Jeng‐Yu

doi:10.1021/acsaem.8b02219

Cited by 24 publications

(14 citation statements)

References 48 publications

(83 reference statements)

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“…Such improvements in the spiro-OMeTAD films have boosted both open-circuit voltage (V oc ) and short-circuit current ( J sc ), pushing the efficiency of the PVSC to 20.03%. [48] Zhang et al introduced copper complexes with hexafluorophosphate (PF6) counter ions that are highly soluble in organic solvents such as chlorobenzene and acetonitrile. [49] A low-cost copper complex such as Cu (I/II)( dmbp) 2 (PF6) 2 (Figure 5)has been proposed as an additive for spiro-OMeTAD.…”

Section: Metal-based Salts and Complexesmentioning

confidence: 99%

Analytical Review of Spiro‐OMeTAD Hole Transport Materials: Paths Toward Stable and Efficient Perovskite Solar Cells

Nakka

Cheng

Aberle

et al. 2022

Adv Energy and Sustain Res

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Organic-inorganic metal halide perovskite solar cells (PVSCs) have experienced rapid development in recent years, with its power conversion efficiency (PCE) improving from 3.8% in 2009 to an impressive 25.7% in 2021. [1] Thus, the metal halide perovskite is currently considered as a promising emerging photovoltaic (PV) material due to its excellent optoelectronic properties such as high optical absorption coefficient, long charge carrier lifetime, and low nonradiative recombination rates. [2] It is believed that the PVSCs can enter the specific PV market segments, such as building-integrated PV, in the coming years after upscaling the device fabrication and achieving decent device operational stability.The pioneer work of PVSCs was conducted by Miyasaka et al. using CH 3 NH 3 PbBr 3 and CH 3 NH 3 PbI 3 as photoactive materials in the liquid-based dye-sensitized solar cells (DSSCs). [3] The perovskite-based DSSCs achieved an efficiency of 3.8% but exhibited very poor stability because the metal halide perovskites are chemically reactive to the liquid electrolyte. Subsequently, the PCE of perovskite-based DSSCs was further improved to 6.5% using CH 3 NH 3 PbI 3 quantum dots (QDs) as the light absorber in 2011. Although the authors demonstrated enhanced efficiency by this way, the device performance degraded by 80% upon continuous irradiation for only 10 min, because the redox electrolyte dissolved the perovskite QDs due to its strong polar property. [4] To resolve this issue, Park et al. proposed a transition from DSSC to a solid-state PVSC by introducing a solid-state organic hole conductor, namely, 2,2',7,7'-tetrakis[N,N-di(4-methoxyphenyl)amino]-9-9'spirobifluorene (spiro-OMeTAD). The solid-state hole conductor provides efficient hole extraction from the perovskite layer to the electrode, achieving a record PCE of 9.7%. [5] In addition, the stability of such solid-state PVSCs has improved to over 500 h under AM 1.5 G light illumination. This research has triggered rapid progress in the research activities on PVSCs and the related publications have increased exponentially since 2012. The yearly progress of PVSC is summarized in Figure 1 and the current certified record PCE of PVSCs is 25.7%, achieved by Ulsan National Institute of Science and Technology (UNIST) in 2021. [1]

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Section: Metal-based Salts and Complexesmentioning

confidence: 99%

Analytical Review of Spiro‐OMeTAD Hole Transport Materials: Paths Toward Stable and Efficient Perovskite Solar Cells

Nakka

Cheng

Aberle

et al. 2022

Adv Energy and Sustain Res

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“…36 The degree of energy level shift (∼0.2 eV) is highly consistent with the previous reports about the spiro-OMeTAD doping. 37,38 This favorable energy level match between the perovskite and HTL would facilitate the hole injection at the perovskite/HTL interface. 38 Furthermore, the conductivity of spiro-OMeTAD films doped with various anions was evaluated using four-point probe electrical measurements (Figure 2b and Table S2) because the conductivity of the spiro-OMeTAD is a crucial factor for determining the photovoltaic performance of PSCs.…”

Section: ■ Results and Discussionmentioning

confidence: 99%

Understanding the Influence of Anion Exchange on the Hole Transport Layer for Efficient and Humidity-Stable Perovskite Solar Cells

Goh

Jang

et al. 2021

ACS Sustainable Chem. Eng.

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High-performance perovskite solar cells (PSCs) are readily degradable by moisture, leading to high demand for a water-repelling efficient hole transport layer (HTL). In this study, we proposed an anionexchange approach to replace the conventional hygroscopic dopant anion bis(trifluoromethanesulfonyl)imide (TFSI − )with a hydrophobic dopant anion capable of effectively doping into a 2,2′,7,7′-tetrakis(N,N-di-pmethoxyphenylamine)-9,9′-spirobifluorene (spiro-OMeTAD) matrix. By varying the size of dopant anions, we successfully controlled electrostatic interactions between spiro-OMeTAD and the dopant anion. Hexafluorophosphate (PF 6 − ) demonstrated the highest p-doping anion-exchange capability because the optimal-sized PF 6− enabled a strong electrostatic interaction between spiro-OMeTAD •+ and PF 6 − while resulting in poor affinity between Li + and PF 6 − . The resulting PF 6 − -doped spiro-OMeTAD HTL not only produced favorable energy band alignment with perovskite but also improved film conductivity. Correspondingly, the PSCs based on the PF 6 − -doped HTL exhibited a higher power conversion efficiency (PCE) of 20.78% than the reference TFSI − -based PSCs of 19.04%. Besides device performance, the superior hydrophobic nature of PF 6 − enabled the HTL to prevent water penetration into the perovskite layer, improving long-term stability against moisture. The PF 6 − -based PSCs exhibited enhanced humidity stability while maintaining 92% of the initial PCE for 1180 h at a relative humidity of 25% under ambient conditions.

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“…To quantify the density of trap states in these perovskite films, space‐charge‐limited current (SCLC) measurements in the dark were performed as shown in Figure 2e and the sample structure of the electron only device was FTO/TiO 2 /perovskite/PCBM/Ag. The trap‐state density ( n trap ) can be calculated based on the equation n trap = (2 εε 0 V TFL )/( eL 2 ),47–50 in which ε and ε 0 represent the relative dielectric constant of the perovskite film and the vacuum permittivity (8.854 × 10 −14 F cm −1 ),51,52 V TFL can be extracted from the kink point between the ohmic and the trap‐filled limit region, e is the elementary charge, and L is the thickness of the perovskite layer obtained from the cross‐sectional SEM image. The extracted trap densities are 1.06 × 10 16 , 1.80 × 10 16 , and 0.48 × 10 16 cm −3 for the pristine, TGA‐modified, and GA‐modified perovskite films, respectively.…”

Section: Resultsmentioning

confidence: 99%

Solvent Engineering Using a Volatile Solid for Highly Efficient and Stable Perovskite Solar Cells

Cui

et al. 2020

Advanced Science

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A strategy for efficaciously regulating perovskite crystallinity is proposed by using a volatile solid glycolic acid (HOCH2COOH, GA) in an FA0.85MA0.15PbI3 (FA: HC(NH2)2; MA: CH3NH3) perovskite precursor solution that is different from the common additive approach. Accompanied with the first dimethyl sulfoxide sublimation process, the subsequent sublimation of GA before 150 °C in the FA0.85MA0.15PbI3 perovskite film can artfully regulate the perovskite crystallinity without any residual after annealing. The improved film formation upon GA modification induced by the strong interaction between GA and Pb2+ delivers a champion power conversion efficiency (PCE) as high as 21.32%. In order to investigate the role of volatility in perovskite solar cells (PSCs), nonvolatile thioglycolic acid (HSCH2COOH, TGA) with a similar structure to GA is utilized as an additive reference. Large perovskite grains are obtained by TGA modification but with obvious pinholes, which directly leads to an increased defect density accompanied by a decline in PCE. Encouragingly, the champion PCE achieved for GA‐based PSC device (21.32%) is almost 13% or 20% higher than those of the control device or TGA‐based device. In addition, GA‐modified PSCs exhibit the best stability in light‐, thermal‐, and humidity‐based tests due to the improved film formation.

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Dual Functional Doping of KMnO₄ in Spiro-OMeTAD for Highly Effective Planar Perovskite Solar Cells

Cited by 24 publications

References 48 publications

Analytical Review of Spiro‐OMeTAD Hole Transport Materials: Paths Toward Stable and Efficient Perovskite Solar Cells

Analytical Review of Spiro‐OMeTAD Hole Transport Materials: Paths Toward Stable and Efficient Perovskite Solar Cells

Understanding the Influence of Anion Exchange on the Hole Transport Layer for Efficient and Humidity-Stable Perovskite Solar Cells

Solvent Engineering Using a Volatile Solid for Highly Efficient and Stable Perovskite Solar Cells

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Dual Functional Doping of KMnO4 in Spiro-OMeTAD for Highly Effective Planar Perovskite Solar Cells

Cited by 24 publications

References 48 publications

Analytical Review of Spiro‐OMeTAD Hole Transport Materials: Paths Toward Stable and Efficient Perovskite Solar Cells

Analytical Review of Spiro‐OMeTAD Hole Transport Materials: Paths Toward Stable and Efficient Perovskite Solar Cells

Understanding the Influence of Anion Exchange on the Hole Transport Layer for Efficient and Humidity-Stable Perovskite Solar Cells

Solvent Engineering Using a Volatile Solid for Highly Efficient and Stable Perovskite Solar Cells

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Dual Functional Doping of KMnO₄ in Spiro-OMeTAD for Highly Effective Planar Perovskite Solar Cells