| 1. |
- Bogachuk, Dmitry, et al.
(författare)
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Perovskite Solar Cells with Carbon-Based Electrodes - Quantification of Losses and Strategies to Overcome Them
- 2022
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Ingår i: Advanced Energy Materials. - : John Wiley & Sons. - 1614-6832 .- 1614-6840. ; 12:10
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Tidskriftsartikel (refereegranskat)abstract
- Carbon-based electrodes represent a promising approach to improve stability and up-scalability of perovskite photovoltaics. The temperature at which these contacts are processed defines the absorber grain size of the perovskite solar cell: in cells with low-temperature carbon-based electrodes (L-CPSCs), layer-by-layer deposition is possible, allowing perovskite crystals to be large (>100 nm), while in cells with high-temperature carbon-based contacts (H-CPSCs), crystals are constrained to 10-20 nm in size. To enhance the power conversion efficiency of these devices, the main loss mechanisms are identified for both systems. Measurements of charge carrier lifetime, quasi-Fermi level splitting (QFLS) and light-intensity-dependent behavior, supported by numerical simulations, clearly demonstrate that H-CPSCs strongly suffer from non-radiative losses in the perovskite absorber, primarily due to numerous grain boundaries. In contrast, large crystals of L-CPSCs provide a long carrier lifetime (1.8 mu s) and exceptionally high QFLS of 1.21 eV for an absorber bandgap of 1.6 eV. These favorable characteristics explain the remarkable open-circuit voltage of over 1.1 V in hole-selective layer-free L-CPSCs. However, the low photon absorption and poor charge transport in these cells limit their potential. Finally, effective strategies are provided to reduce non-radiative losses in H-CPSCs, transport losses in L-CPSCs, and to improve photon management in both cell types.
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| 2. |
- Bogachuk, Dmitry, et al.
(författare)
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Rethinking Electrochemical Deposition of Nickel Oxide for Photovoltaic Applications
- 2024
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Ingår i: Solar RRL. - : John Wiley & Sons. - 2367-198X. ; 8:2
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Tidskriftsartikel (refereegranskat)abstract
- A thin layer of sputtered or wet-processed nickel oxide (NiOx) is often used to fabricate perovskite solar cells (PSCs). Remarkably, NiOx can also be deposited by a recently developed electrochemical method, which is considered promising due to its short processing time, absence of high-vacuum conditions, and ease of manufacturing. Such electrochemically deposited NiOx (eleNiOx) is obtained by applying an electric bias to the front electrode of a PSC or perovskite solar module (PSM). Therefore, the electrode sheet resistance affects the current distribution through it, creating a gradient in the amount of charge provided for the electrochemical reaction. Consequently, this leads to the inhomogeneity in the formed eleNiOx, which has numerous implications on the final photovoltaic performance of PSMs. In this work, the interdependencies between the electrode sheet resistance, current distribution, eleNiOx thickness gradient, and the caused power losses of large area PSMs are discussed. By coupling the experimental findings with our numerical simulations, it is found that heterogeneity in surface potential of even small-sized modules can lead to severe differences in local eleNiOx thickness and photovoltaic performance. Therefore the potential drop across the front electrode is an inherent problem of this deposition method and potential approaches are proposed to minimize it. The synergy between several numerical simulation methods and the experimental work provides an additional critical insight into the electrochemical deposition process of nickel oxide and how important it is for the performance and stability of the large-area perovskite photovoltaic modules. It is believed that the conclusions drawn from this study are universally applicable to other electrochemically deposited layers as well.image (c) 2023 WILEY-VCH GmbH
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| 3. |
- Campanari, Valerio, et al.
(författare)
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Reevaluation of Photoluminescence Intensity as an Indicator of Efficiency in Perovskite Solar Cells
- 2022
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Ingår i: Solar RRL. - : John Wiley & Sons. - 2367-198X. ; 6:8
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Tidskriftsartikel (refereegranskat)abstract
- The photoluminescence (PL) intensity is often used as an indicator of the performance of perovskite solar cells and indeed the PL technique is often used for the characterization of these devices and their constituent materials. Herein, a systematic approach is presented to the comparison of the conversion efficiency and the PL intensity of a cell in both open-circuit (OC) and short-circuit (SC) conditions and its application to multiple heterogeneous devices. It is shown that the quenching of the PL observed in SC conditions is a good parameter to assess the device efficiency. The authors explain the dependence of the PL quenching ratio between OC and SC on the cell efficiency with a simple model that is also able to estimate the carrier extraction time of a device.
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| 4. |
- Choi, Hyeon-Seo, et al.
(författare)
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Oriented Crystal Growth during Perovskite Surface Reconstruction
- 2022
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Ingår i: ACS Applied Materials and Interfaces. - : American Chemical Society (ACS). - 1944-8244 .- 1944-8252. ; 14:45, s. 51149-51156
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Tidskriftsartikel (refereegranskat)abstract
- Surface passivation has become a key strategy for an improvement in power conversion efficiency (PCE) of perovskite solar cells (PSCs) since PSCs experienced a steep increase in PCE and reached a comparably matured point. Recently, surface passivation using a mixed salt of fluorinated alkyl ammonium iodide and formamidinium bromide demon-strated a remarkable improvement in both performance and stability, which can be tuned by the length of the alkyl chain. Nevertheless, the role of the alkyl chain in manipulating surface-limited crystal growth was not fully understood, preventing a further progress in interface control. In this study, we found that the length of the fluorine-substituted alkyl chain governed the crystal formation dynamics by manipulating surface tensions of different crystal orientations. The overall enhancement of the (001) plane, being the most favored, commonly resulted from the surface reformation of the perovskite film regardless of the chain length, while the highly oriented (001) over (111) was monitored with a particular chain length. The enhanced crystal orientation during surface recrystallization was responsible for the low trap density and thus effectively suppressed charge recombination at the interface, resulting in a considerable increase in open-circuit voltage and fill factor.
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| 5. |
- Kim, YeonJu, et al.
(författare)
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Additives-free indolo[3,2-b]carbazole-based hole-transporting materials for perovskite solar cells with three yeses : Stability, efficiency, simplicity
- 2022
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Ingår i: Nano Energy. - : Elsevier. - 2211-2855 .- 2211-3282. ; 101
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Tidskriftsartikel (refereegranskat)abstract
- Indolo[3,2-b]carbazole-based hole transporting materials (HTM1-3) are developed for dopant-free pemvskite solar cells (PSCs). The newly synthesized compounds are studied as alternatives of conventional hole-transporting materials which typically require additives, are characterized by low resistivity to penetration of water, complicated synthesis and purification. The influence of substituents of derivatives of indolo[3,2-b]carbazole on their physical properties, e.g. ionization potentials, hole mobilities, the temperatures of thermal transitions, is investigated using experimental and theoretical tools. Ionization potentials in the order HTM2 < HTM1 < HTM3 indicate good energy level alignment with the valence band maximum of the pemvskite layer. Time-of-flight hole mobilities in the order HTM3 (5.26 x 10(-3) cm(2)V(-1)s(-1)) > HTM1 (1.1 x 10(-3) cm(2)V(-1)s(-1)) > HTM2 (0.55 x 10(-3) cm(2)V(-1)s(-1)) without additives indicate good hole transporting properties, principally stemming from their small degrees of energetic disorder following the order HTM3 (73.4 meV) similar to HTM2 (73.2 meV) > HTM1 (59.5 meV). The influence of different combinations of these parameters results in the different power conversion efficiencies of the developed dopant-free PSCs: [19.45% for the device containing HTM2] similar to [18.75% for PCS containing HTM3] > [14.46% for the device containing HTM1]. The devices demonstrate considerably higher stability and practically comparable efficiency as additives-containing reference PSCs with conventional hole-transporting material spiro-OMeTAD.
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| 6. |
- Ren, Yameng, et al.
(författare)
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Hydroxamic acid pre-adsorption raises the efficiency of cosensitized solar cells
- 2023
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Ingår i: Nature. - : Springer Nature. - 0028-0836 .- 1476-4687. ; 613:7942, s. 60-65
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Tidskriftsartikel (refereegranskat)abstract
- Dye-sensitized solar cells (DSCs) convert light into electricity by using photosensitizers adsorbed on the surface of nanocrystalline mesoporous titanium dioxide (TiO2) films along with electrolytes or solid charge-transport materials(1-3). They possess many features including transparency, multicolour and low-cost fabrication, and are being deployed in glass facades, skylights and greenhouses(4). Recent development of sensitizers(5-10), redox mediators(11-13) and device structures(14) has improved the performance of DSCs, particularly under ambient light conditions(14-17). To further enhance their efficiency, it is pivotal to control the assembly of dye molecules on the surface of TiO2 to favour charge generation. Here we report a route of pre-adsorbing a monolayer of a hydroxamic acid derivative on the surface of TiO2 to improve the dye molecular packing and photovoltaic performance of two newly designed co-adsorbed sensitizers that harvest light quantitatively across the entire visible domain. The best performing cosensitized solar cells exhibited a power conversion efficiency of 15.2% (which has been independently confirmed) under a standard air mass of 1.5 global simulated sunlight, and showed long-term operational stability (500 h). Devices with a larger active area of 2.8 cm(2) exhibited a power conversion efficiency of 28.4% to 30.2% over a wide range of ambient light intensities, along with high stability. Our findings pave the way for facile access to high-performance DSCs and offer promising prospects for applications as power supplies and battery replacements for low-power electronic devices(18-20) that use ambient light as their energy source.
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| 7. |
- Suo, Jiajia, et al.
(författare)
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Interfacial engineering from material to solvent : A mechanistic understanding on stabilizing alpha-formamidinium lead triiodide perovskite photovoltaics
- 2022
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Ingår i: Nano Energy. - : Elsevier. - 2211-2855 .- 2211-3282. ; 94
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Tidskriftsartikel (refereegranskat)abstract
- Formamidinium lead triiodide (FAPbI3) has recently been considered as the most promising candidate to achieve highly efficient perovskite solar cells (PSCs). Excitingly, the state-of-the-art highest efficiency of FAPbI3 based PSCs have reached over 25%. However, their device stability still lags behind other compositions of mixed-cation and mixed-halide perovskites. Interfacial engineering is a very powerful method to address this issue and passivation agents have been intensively developed, however there is a lack of in-depth understanding regarding the solvent selection during post-treatment. Here, we employed cyclohexylmethylammonium iodide (CMAI) as passivation agent, which is investigated using either isopropanol (IPA) or chloroform (CF) as carrier mediator to study the solvent influence on the stabilization of FAPbI3. We observed a suppressed-defect perovskite surface toward distinguished composition with 2D CMA2PbI4 domain and CMAI domain induced by IPA and CF, respectively. Remarkably, post-treatment with solution of CMAI in CF creates a strain-free environment on the perovskite surface, leading to an improved efficiency of approaching 24% and concurrently an extraordinarily stable alpha-phase FAPbI3 PSCs under operation condition, retaining 95% of its initial efficiency after 1050-hour aging. Our resulting device stability is one of the most stable FAPbI3 based PSCs reported in literature.
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| 8. |
- Suo, Jiajia, et al.
(författare)
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Multifunctional sulfonium-based treatment for perovskite solar cells with less than 1% efficiency loss over 4,500-h operational stability tests
- 2024
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Ingår i: Nature Energy. - : NATURE PORTFOLIO. - 2058-7546.
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Tidskriftsartikel (refereegranskat)abstract
- The stabilization of grain boundaries and surfaces of the perovskite layer is critical to extend the durability of perovskite solar cells. Here we introduced a sulfonium-based molecule, dimethylphenethylsulfonium iodide (DMPESI), for the post-deposition treatment of formamidinium lead iodide perovskite films. The treated films show improved stability upon light soaking and remains in the black alpha phase after two years ageing under ambient condition without encapsulation. The DMPESI-treated perovskite solar cells show less than 1% performance loss after more than 4,500 h at maximum power point tracking, yielding a theoretical T80 of over nine years under continuous 1-sun illumination. The solar cells also display less than 5% power conversion efficiency drops under various ageing conditions, including 100 thermal cycles between 25 degrees C and 85 degrees C and an 1,050-h damp heat test. Suo et al. show that sulfonium-based molecules afford formamidinium lead iodide perovskites protection against environmental stress factors, improved phase stability and solar cells retaining efficiency over 4,500-h operational stability tests.
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| 9. |
- Suo, Jiajia, et al.
(författare)
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Passivation Strategies through Surface Reconstruction toward Highly Efficient and Stable Perovskite Solar Cells on n-i-p Architecture
- 2021
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Ingår i: Energies. - : MDPI. - 1996-1073. ; 14:16
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Forskningsöversikt (refereegranskat)abstract
- Perovskite solar cells have achieved remarkable enhancement in their performance in recent years. However, to get an entrance to the photovoltaic market, great effort is still necessary to further improve their efficiency as well as their long-term stability under various conditions. Among various types of approaches (including compositional engineering, dopant engineering, self-assembled monolayers (SAMs), et al.), interfacial engineering through passivation treatment has been considered as one of the most effective strategies to reduce the non-radiative recombination within the PSCs. Thus, this short review summaries recent efforts on chemical interfacial passivation strategies from a different perspective owing to their common phenomena of reconstructing the perovskite surface via the formation of three-dimensional perovskite, low-dimensional perovskite and synergistic effect provided by a mixed-salt passivation system, respectively.
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| 10. |
- Suo, Jiajia, et al.
(författare)
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Surface Reconstruction Engineering with Synergistic Effect of Mixed-Salt Passivation Treatment toward Efficient and Stable Perovskite Solar Cells
- 2021
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Ingår i: Advanced Functional Materials. - : John Wiley & Sons. - 1616-301X .- 1616-3028. ; 31:34
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Tidskriftsartikel (refereegranskat)abstract
- Surface passivation treatment is a widely used strategy to resolve trap-mediated nonradiative recombination toward high-efficiency metal-halide perovskite photovoltaics. However, a lack of passivation with mixture treatment has been investigated, as well as an in-depth understanding of its passivation mechanism. Here, a systematic study on a mixed-salt passivation strategy of formamidinium bromide (FABr) coupled with different F-substituted alkyl lengths of ammonium iodide is demonstrated. It is obtained better device performance with decreasing chain length of the F-substituted alkyl ammonium iodide in the presence of FABr. Moreover, they unraveled a synergistic passivation mechanism of the mixed-salt treatment through surface reconstruction engineering, where FABr dominates the reformation of the perovskite surface via reacting with the excess PbI2. Meanwhile, ammonium iodide passivates the perovskite grain boundaries both on the surface and top perovskite bulk through penetration. This synergistic passivation engineer results in a high-quality perovskite surface with fewer defects and suppressed ion migration, leading to a champion efficiency of 23.5% with mixed-salt treatment. In addition, the introduction of the moisture resisted F-substituted groups presents a more hydrophobic perovskite surface, thus enabling the decorated devices with excellent long-term stability under a high humid atmosphere as well as operational conditions.
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