| 1. |
- Hawash, Zafer, et al.
(författare)
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Recent Advances in Spiro-MeOTAD Hole Transport Material and Its Applications in Organic-Inorganic Halide Perovskite Solar Cells
- 2018
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Ingår i: Advanced Materials Interfaces. - : John Wiley & Sons. - 2196-7350. ; 5:1
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Forskningsöversikt (refereegranskat)abstract
- 2,2,7,7-tetrakis-(N,N-di-4-methoxyphenylamino)-9,9-spirobifluorene (spiro-MeOTAD) hole transport material (HTM) is a milestone in the history of perovskite solar cells (PSCs). Proper choice of HTMs is key factor for efficient charge extraction and stability in solar cells. Spiro-MeOTAD is proven to be the most suitable HTM for testing PSCs due to its facile implementation and high performance. Similarly, spiro-MeOTAD is receiving attention in other applications other than in solar cells due to its desirable properties. However, spiro-MeOTAD is under debate regarding the topics of cost-performance, long-term stability, degradation issues (induced by temperature, additives, film quality, and environmental conditions), coating technologies compatibility, reliance on additives, and hysteresis. In this review, the advent of spiro-MeOTAD, and related aforementioned issues about spiro-MeOTAD are discussed. In addition, spiro-MeOTAD properties, alternative and new additives, other applications, and new HTMs that is comparable or outperforms spiro-MeOTAD in PSCs are summarized. In the outlook, the future research directions based on reported results that warrant further investigations are outlined.
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| 2. |
- Juarez-Perez, Emilio J., et al.
(författare)
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Photodecomposition and thermal decomposition in methylammonium halide lead perovskites and inferred design principles to increase photovoltaic device stability
- 2018
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Ingår i: Journal of Materials Chemistry A. - : Royal Society of Chemistry. - 2050-7488 .- 2050-7496. ; 6:20, s. 9604-9612
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Tidskriftsartikel (refereegranskat)abstract
- Hybrid lead halide perovskites have emerged as promising active materials for photovoltaic cells. Although superb efficiencies have been achieved, it is widely recognized that long-term stability is a key challenge intimately determining the future development of perovskite-based photovoltaic technology. Herein, we present reversible and irreversible photodecomposition reactions of methylammonium lead iodide (MAPbI(3)). Simulated sunlight irradiation and temperature (40-80 degrees C) corresponding to solar cell working conditions lead to three degradation pathways: (1) CH3NH2 + HI (identified as the reversible path), (2) NH3 + CH3I (the irreversible or detrimental path), and (3) a reversible Pb(0) + I-2(g) photodecomposition reaction. If only the reversible reactions (1) and (3) take place and reaction (2) can be avoided, encapsulated MAPbI(3) can be regenerated during the off-illumination timeframe. Therefore, to further improve operational stability in hybrid perovskite solar cells, detailed understanding of how to mitigate photodegradation and thermal degradation processes is necessary. First, encapsulation of the device is necessary not only to avoid contact of the perovskite with ambient air, but also to prevent leakage of volatile products released from the perovskite. Second, careful selection of the organic cations in the compositional formula of the perovskite is necessary to avoid irreversible reactions. Third, selective contacts must be as chemically inert as possible toward the volatile released products. Finally, hybrid halide perovskite materials are speculated to undergo a dynamic formation and decomposition process; this can gradually decrease the crystalline grain size of the perovskite with time; therefore, efforts to deposit highly crystalline perovskites with large crystal sizes may fail to increase the long-term stability of photovoltaic devices.
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| 3. |
- Liang, Jia, et al.
(författare)
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Enhancing Optical, Electronic, Crystalline, and Morphological Properties of Cesium Lead Halide by Mn Substitution for High-Stability All-Inorganic Perovskite Solar Cells with Carbon Electrodes
- 2018
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Ingår i: Advanced Energy Materials. - : Wiley-VCH Verlagsgesellschaft. - 1614-6832 .- 1614-6840. ; 8:20
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Tidskriftsartikel (refereegranskat)abstract
- In this work all-inorganic perovskite CsPbIBr2 are doped with Mn to compensate their shortcomings in band structure for the application of perovskite solar cells (PSCs). The novel Mn-doped all-inorganic perovskites, CsPb1-xMnxI1+2xBr2-2x, are prepared in ambient atmosphere. As the concentration of Mn2+ ions increases, the bandgaps of CsPb1-xMnxI1+2xBr2-2x decrease from 1.89 to 1.75 eV. Additionally, when the concentration of Mn dopants is appropriate, this novel Mn-doped all-inorganic perovskite film shows better crystallinity and morphology than its undoped counterpart. These advantages alleviate the energy loss in hole transfer and facilitate the charge-transfer in perovskites, therefore, PSCs based on these novel CsPb1-xMnxI1+2xBr2-2x perovskite films display better photovoltaic performance than the undoped CsPbIBr2 perovskite films. The reference CsPbIBr2 cell reaches a power conversion efficiency (PCE) of 6.14%, comparable with the previous reports. The CsPb1-xMnxI1+2xBr2-2x cells reach the highest PCE of 7.36% (when x= 0.005), an increase of 19.9% in PCE. Furthermore, the encapsulated CsPb0.995Mn0.005I1.01Br1.99 cells exhibit good stability in ambient atmosphere. The storage stability measurements on the encapsulated PSCs reveal that PCE is dropped by only 8% of the initial value after >300 h in ambient. Such improved efficiency and stability are achieved using low-cost carbon electrodes (without expensive hole transport materials and Au electrodes).
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| 4. |
- Liu, Zonghao, et al.
(författare)
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Gas-solid reaction based over one-micrometer thick stable perovskite films for efficient solar cells and modules
- 2018
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Ingår i: Nature Communications. - : Nature Publishing Group. - 2041-1723. ; 9
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Tidskriftsartikel (refereegranskat)abstract
- Besides high efficiency, the stability and reproducibility of perovskite solar cells (PSCs) are also key for their commercialization. Herein, we report a simple perovskite formation method to fabricate perovskite films with thickness over 1 mu m in ambient condition on the basis of the fast gas-solid reaction of chlorine-incorporated hydrogen lead triiodide and methylamine gas. The resultant thick and smooth chlorine-incorporated perovskite films exhibit full coverage, improved crystallinity, low surface roughness and low thickness variation. The resultant PSCs achieve an average power conversion efficiency of 19.1 +/- 0.4% with good reproducibility. Meanwhile, this method enables an active area efficiency of 15.3% for 5 cmx 5 cm solar modules. The un-encapsulated PSCs exhibit an excellent T-80 lifetime exceeding 1600 h under continuous operation conditions in dry nitrogen environment.
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| 5. |
- Ono, Luis K., et al.
(författare)
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The influence of secondary solvents on the morphology of a spiro-MeOTAD hole transport layer for lead halide perovskite solar cells
- 2018
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Ingår i: Journal of Physics D. - : Institute of Physics (IOP). - 0022-3727 .- 1361-6463. ; 51:29
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Tidskriftsartikel (refereegranskat)abstract
- 2,2 ',7,7 '-tetrakis(N,N-di-p-methoxyphenylamine)-9,9 '-spirobifluorene (spiro-MeOTAD) has been widely employed as a hole transport layer (HTL) in perovskite-based solar cells. Despite high efficiencies, issues have been reported regarding solution processed spiro-MeOTAD HTL such as pinholes and the strong dependence of electrical properties upon air exposure, which poses challenges for solar cell stability and reproducibility. In this work, we perform a systematic study to unravel the fundamental mechanisms for the generation of pinholes in solution-processed spiro-MeOTAD films. The formation of pinholes is closely related to the presence of small amounts of secondary solvents (e.g. H2O, 2-methyl-2-butene or amylene employed as a stabilizer, absorbed moisture from ambient, etc), which have low miscibility in the primary solvent generally used to dissolve spiro-MeOTAD (e.g. chlorobenzene). The above findings are not only applicable for spiro-MeOTAD (a small organic molecule), but also applicable to polystyrene (a polymer). The influence of secondary solvents in the primary solvents is the main cause for the generation of pinholes on film morphology. Our findings are of direct relevance for the reproducibility and stability in perovskite solar cells and can be extended to many other spin-coated or drop-casted thin films.
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