Identifying the optimum thickness of electron transport layers for highly efficient perovskite planar solar cells

Lü, Hao; Ma, Yulong; Gu, Bangkai; Tian, Wei; Li, Liang

doi:10.1039/c5ta03686k

Cited by 97 publications

(49 citation statements)

References 38 publications

(63 reference statements)

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“…Regarding polymer based cells, in this study we have surpassed the reported power conversion efficiency (PCE) record for PCPDTBT acting as HTM 20 , while for P3HT and PTB7, the efficiencies obtained are similar to the best efficiencies reported avoiding the use of dopants 31, 32 .…”

Section: Resultssupporting

confidence: 47%

Charge Injection, Carriers Recombination and HOMO Energy Level Relationship in Perovskite Solar Cells

Jiménez‐López

Cambarau

Cabau

et al. 2017

Sci Rep

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We present a comparative study between a series of well-known semiconductor polymers, used in efficient organic solar cells as hole transport materials (HTM), and the state-of-the art material used as hole transport material in perovskite solar cells: the spiro-OMeTAD. The observed differences in solar cell efficiencies are studied in depth using advanced photoinduced spectroscopic techniques under working illumination conditions. We have observed that there is no correlation between the highest occupied molecular orbital (HOMO) energy levels of the organic semiconductors and the measured open-circuit voltage (VOC). For instance, spiro-OMeTAD and P3HT have a comparable HOMO level of ~5.2 eV vs vacuum even though a difference in VOC of around 200 mV is recorded. This difference is in good agreement with the shift observed for the charge vs voltage measurements. Moreover, hole transfer from the perovskite to the HTM, estimated qualitatively from fluorescence quenching and emission lifetime, seems less efficient for the polymeric HTMs. Finally, the recombination currents from all devices were estimated by using the measured charge (calculated using photoinduced differential charging) and the carriers’ lifetime and their value resulted in accordance with the registered short-circuit currents (JSC) at 1 sun.

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Section: Resultssupporting

confidence: 47%

Charge Injection, Carriers Recombination and HOMO Energy Level Relationship in Perovskite Solar Cells

Jiménez‐López

Cambarau

Cabau

et al. 2017

Sci Rep

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“…There were several attempts in the application of real dopant-free homopolymer as HTMs. [107] At the same time, the classic conductive polymer ink poly(3,4-ethylene dioxythiophene):poly(styrene sulfonic acid) (PEDOT:PSS) played a leading role in the construction of a p-i-n type planar perovskite solar cell. Recently, using pristine P3HT-based HTM, a PCE of 13.6% was achieved in a device structure of glass/FTO/ALD-TiO 2 /CH 3 NH 3 PbI 3−x Cl x /P3HT/ Ag.…”

Section: Polymers Materialsmentioning

confidence: 99%

Less is More: Dopant‐Free Hole Transporting Materials for High‐Efficiency Perovskite Solar Cells

Zhou

Wen

Gao

2018

Advanced Energy Materials

246

217

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years, the demands for reducing the fabrication costs and the energy payback time of photovoltaic devices led to the invention of emerging third-generation PV technologies, such as dye-sensitized solar cells (DSSCs), organic photovoltaic (OPV), quantum dots solar cells, and the latest perovskite solar cells (PSCs). Among them, PSC is the only technology that combines both merits of low processing energy cost and high power conversion efficiency (PCE), which makes it possible to replace the silicon-based PV technology.Since the first reports by Bach and Grätzel et al. about the use of 2,2′,7,7′tetrakis(N,N-di-p-methoxyphenylamine)-9,9′-spirobifluorene (spiro-OMeTAD) as the hole-transporting material (HTM) in solid-state DSSCs (ssDSSC), spiro-OMeTAD becomes the benchmark of all the new HTMs developed for ssDSSC and PSCs. Contrary to the popular myth, spiro-OMeTAD is not completely amorphous but a semi-crystalline organic p-type semiconductor with a glass transition temperature of 121 °C and a melting point of 246 °C. [1] Its chemical structure is shown in Figure 1a and Grätzel's lab first revealed the crystal structure in 2014 [2] ( Figure 1b). It has a large bandgap of 2.98 eV and yields almost colorless thin films when deposited from solution in organic solvents such as toluene or chlorobenzene. The first oxidation potential of spiro-OMeTAD is found to be approximately −5.1 eV as derived from electrochemical and photoelectron spectroscopy measurements. [3] In the case of the solid-state PSCs reported since 2012, [4,5] the PCE of lab-made devices has increased from 9.7% [6] to above 21% [7] in 2017, owing to the improvement in the perovskite composition and device engineering. However, on account of several desirable properties, (i) favorable glass transition temperature; (ii) reasonable solubility; (iii) proper ionization potential; (iii) low visible light absorption; and (iv) appropriate solid-state morphology, spiro-OMeTAD has remained as the material of choice when high PCEs are demanded. Due to the fact that spiro-OMeTAD suffers from a relatively low conductivity in its pristine form, all the eyecatching PCEs were achieved by adding additives and/or dopants-a standard technique used to tune the electrical properties of both organic and inorganic semiconductors. Typical additives including 4-tert-butylpyridine (TBP) and lithium bis(trifluoromethyl sulfonyl)imide (LiTFSI) were added to the spin-coating formulation of spiro-MeOTAD and Perovskite solar cells have delivered power conversion efficiency beyond 22% in less than seven years, implying the potential for the paradigm shift of lowcost photovoltaics with high efficiency and low embedded energy. Besides the "perovskite fever," the development of new hole transport materials (HTM), especially dopant-free HTMs, is another research hotspot. This is because the currently used HTMs, such as spiro-OMeTAD derivatives, require additional chemical doping process to ensure sufficient conductivity and proper ionic potential level for efficient hole transport and colle...

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“…This parameter could affect the performance of PEC cells as thick film will increase the series resistance which can reduce the current and in some cases, increase charge recombination rate. Meanwhile, thin layer of photoanode not only reduce light absorption which subsequently reduce the number of exciton generation, but also lead to incomplete surface coverage and pinholes formation which increases the possibility of charge carrier recombination . Hence, the right thickness of photoanode is necessary to ensure high photocatalytic activity in solar water splitting.…”

Section: Introductionmentioning

confidence: 99%

Effect of Film Thickness on Photoelectrochemical Performance of SnO₂ Prepared via AACVD

Noh

Soh

Riza

et al. 2018

Physica Status Solidi (b)

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Tin (IV) oxide (SnO 2 ) is a stable semiconductor and has been used in a wide range of applications. In this work, aerosol-assisted chemical vapor deposition (AACVD) technique is employed to deposit SnO 2 thin film with different layer thicknesses by controlling the deposition time. The morphological and optical properties of SnO 2 layer are investigated thoroughly to understand the relationship between the deposition time and SnO 2 performance in photoelectrochemical cells. The bandgap energy of all SnO 2 thin films is determined to be 3.65 eV. However, from linear sweep voltammetry (LSV) analysis, it is found that SnO 2 layer deposited for 15 min, which produced a layer with thickness of about 50 nm, showed the best photocurrent performance (30.7 mA cm À2 at 1.0 V vs. Ag/AgCl) compared to their thinner or thicker counterparts. The right thickness enables the formation of a film with complete surface coverage, which effectively prevents current leakage and allows optimum light absorption. Besides, electrochemical impedance spectroscopy (EIS) analysis confirms that 50 nm thick SnO 2 layer possesses fastest electron transfer property compared to thicker or thinner layers.

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Identifying the optimum thickness of electron transport layers for highly efficient perovskite planar solar cells

Cited by 97 publications

References 38 publications

Charge Injection, Carriers Recombination and HOMO Energy Level Relationship in Perovskite Solar Cells

Charge Injection, Carriers Recombination and HOMO Energy Level Relationship in Perovskite Solar Cells

Less is More: Dopant‐Free Hole Transporting Materials for High‐Efficiency Perovskite Solar Cells

Effect of Film Thickness on Photoelectrochemical Performance of SnO₂ Prepared via AACVD

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Identifying the optimum thickness of electron transport layers for highly efficient perovskite planar solar cells

Cited by 97 publications

References 38 publications

Charge Injection, Carriers Recombination and HOMO Energy Level Relationship in Perovskite Solar Cells

Charge Injection, Carriers Recombination and HOMO Energy Level Relationship in Perovskite Solar Cells

Less is More: Dopant‐Free Hole Transporting Materials for High‐Efficiency Perovskite Solar Cells

Effect of Film Thickness on Photoelectrochemical Performance of SnO2 Prepared via AACVD

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Effect of Film Thickness on Photoelectrochemical Performance of SnO₂ Prepared via AACVD