Dopant-free star-shaped hole-transport materials for efficient and stable perovskite solar cells

Wang, Shirong; Zhao, Xiaoming; Yi, Chenyi; Bi, Dongqin; Bi, Xiangdong; Wei, Peng; Liu, Xicheng; Zakeeruddin, Shaik M.; Grätzel, Michaël

doi:10.1016/j.dyepig.2016.08.002

Cited by 88 publications

(68 citation statements)

References 49 publications

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“…47 Thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC) measurements show that these two HTMs have high decomposition temperatures (T d , 402 ºC and 377 ºC for Z25 and Z26, respectively) and glass transition temperatures (T g , 77 ºC and 98 ºC for Z25 and Z26, respectively) (Figure 2c),which are comparable with that of spiroOMeTAD 48 . The hole transporting properties of pristine HTMs were determined from holeonly devices using time-of-flight (TOF) measurements (Figure S9a-c Table S2, Z26 has the lower calculated reorganization energy than Z25, which agrees with the result of TOF test and indicates that the introduction of double bonds can enlarge the favor the transport 49 . The conductivity of these three doped HTMs were determined by a two-contact electrical conductivity set-up.…”

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confidence: 69%

Over 20% PCE perovskite solar cells with superior stability achieved by novel and low-cost hole-transporting materials

et al. 2017

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The exploration of alternative low-cost molecular hole-transporting materials (HTMs) specifically for both high efficient and stable perovskite solar cells (PSCs) is a relatively new research area. Two novel HTMs using the thiophene core were designed and synthesized (Z25 and Z26). The Z26-based perovskite solar cells exhibited a remarkable overall power conversion efficiency (PCE) of 20.1 %, which is comparable to 20.6% obtained by spiro-OMeTAD-based device. Importantly, the devices based-on Z26 show better stability 2 compared to devices based on Z25 and spiro-OMeTAD when aged under ambient air of 30% or 85% relative humidity in the dark and under continuous full sun illumination at maximum power point tracking respectively. The presented results clearly qualify a simple strategy by introduction of double bonds to design hole transporting materials for highly efficient and

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confidence: 69%

Over 20% PCE perovskite solar cells with superior stability achieved by novel and low-cost hole-transporting materials

et al. 2017

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“…[58,59,79] Due to the highly branched structures, these molecules showed insignificant aggregation or crystallization in the solid films. The differences between these molecules are the number of branched arms and their conjugation length.…”

Section: Wwwadvancedsciencenewscommentioning

confidence: 99%

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

Zhou

Wen

Gao

2018

Advanced Energy Materials

252

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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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“…Similar behavior was observed with other reports. [40,50] In the absence of dopants, spiro-MeOTAD based devices generated a PCE of only 3.92% due to the significant lowering of V oc and FF compared to the doped devices. Hysteresis behavior is frequently observed in perovskite solar cells.…”

Section: S1a Esi †)mentioning

confidence: 99%

“…Although inorganic HTMs (CuI and CuSCN) have drawn much attention due to their high hole mobilities and low production cost [21] ,polymeric HTMs, such as conjugated polytriarylamine (PTAA) [22] , poly(3-hexylthiophene-2,5-diyl) (P3HT) [23] etc., have also shown competitive performances in PSCs, small molecular HTMs have advantages of their convenient purification, controllable molecular structures and relatively high efficiency [24] .Regarding small molecule HTMs incorporated with dopants, the PCE of the dopant-free HTM based devices are consistently lying between 10% to 13% [25][26][27][28][29][30][31][32][33][34][35][36] , few are over 15%. [37][38][39][40] Herein, we report the synthesis and characterization of three novel dopant-free 4-Methoxytriphenylamine (MeOTPA) -based HTMs as shown in Figure 1a, Figure 1b and experimental details are given in the Experimental Section. † The new MeOTPA derivatives (Z33,Z34 and Z35) were fully characterized by 1 H NMR spectroscopy, high resolution mass spectrum, and elemental analysis.…”

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Dopant‐Free Donor (D)–π–D–π–D Conjugated Hole‐Transport Materials for Efficient and Stable Perovskite Solar Cells

Liu

et al. 2016

ChemSusChem

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Abstract:Three novel hole transporting materials (HTM) using the 4-Methoxytriphenylamine (MeOTPA) core were designed and synthesized.The HTMs energy levels were tuned to match with perovskite by introducing electron donating groups symmetrically linked with olefinic bonds as the π bridge. The CH 3 NH 3 PbI 3 -based perovskite solar cells exhibited a remarkable overall power conversion efficiency (PCE) of 16.1 % without any dopants and additives based on 4-((E)-4-(bis(4-methoxyphenyl)amino)styryl)-N-(4-((E)-4-(bis(4methoxyphenyl)amino)styryl)phenyl)-N-(4-methoxyphenyl)aniline (Z34) , which is comparable to 16.7 % obtained by p-doped spiro-OMeTAD-based device. Importantly, the devices based-on three HTMs show relatively better stability compared to devices based on spiro-OMeTAD when aged under ambient air of 30% relative humidity in the dark. 2Increasing energy demands and concerns about global warming drive the exploration of clean, inexpensive and renewable energy sources. Recently, the photovoltaic community has witnessed a rapid emergence of a new class of solid-state heterojunction solar cells based on solution-processable organometal halide perovskite absorbers [1][2][3] . The power conversion efficiency (PCE) of solid-state perovskite solar cells (PSCs) has been quickly increased to over 20% [4][5][6] because of their unique characteristics, such as a broad spectral absorption range, large absorption coefficient, high charge carrier mobility and long diffusion length.[2]In the configuration of a PSC, the hole transporting material (HTMs) plays the key role of promoting hole migration, as well as preventing internal charge recombination. [7] A great number of HTMs have been developed and applied in PSCs, including various newly designed, inorganic p-type semiconductors, conducting polymers, as well as small molecule hole conductors [8] . 2,2′,7,7′-tetrakis(N,N-di-p-methoxyphenylamine)-9,9′-spirobifluorene (spiro-OMeTAD) that was well studied in solid state DSCs, continues to exhibit high performance in PSCs. Due to its relatively low hole mobility and its tedious synthesis strongly correlated to its production cost, numerous alternative HTMs have been explored with an aim to replace such a material [9][10][11][12][13][14][15][16][17][18][19][20] . Although inorganic HTMs (CuI and CuSCN) have drawn much attention due to their high hole mobilities and low production cost [21] ,polymeric HTMs, such as conjugated polytriarylamine (PTAA) [22] , poly(3-hexylthiophene-2,5-diyl) (P3HT) [23] etc., have also shown competitive performances in PSCs, small molecular HTMs have advantages of their convenient purification, controllable molecular structures and relatively high efficiency [24] .Regarding small molecule HTMs incorporated with dopants, the PCE of the dopant-free HTM based devices are consistently lying between 10% to 13% [25][26][27][28][29][30][31][32][33][34][35][36] , few are over 15%. [37][38][39][40] Herein, we report the synthesis and characterization of three novel dopant-free 4-Methoxytriphenylamine (Me...

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Dopant-free star-shaped hole-transport materials for efficient and stable perovskite solar cells

Cited by 88 publications

References 49 publications

Over 20% PCE perovskite solar cells with superior stability achieved by novel and low-cost hole-transporting materials

Over 20% PCE perovskite solar cells with superior stability achieved by novel and low-cost hole-transporting materials

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

Dopant‐Free Donor (D)–π–D–π–D Conjugated Hole‐Transport Materials for Efficient and Stable Perovskite Solar Cells

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