Additive engineering to improve the efficiency and stability of inverted planar perovskite solar cells
03 Aug 2018-Journal of Materials Chemistry C (The Royal Society of Chemistry)-Vol. 6, Iss: 30, pp 8234-8241
TL;DR: In this article, formamidine acetate salt (FAAc) is introduced into the precursor solution as an effective additive to greatly improve the quality of perovskite films, and with the addition of 5 mol% FAAc, the PSCs with a bis(4-phenyl)(2,4,6-trimethylphenyl)amine (PTAA) hole extraction layer demonstrate desirable performance in terms of the open-circuit voltage (1.04 V), the shortcircuit current density (23.16 mA cm−2), the
Abstract: Perovskite solar cells (PSCs) have received extensive attention due to their excellent photovoltaic performance. The quality of perovskite films is crucial to device performance, and introducing additives to the precursor solution is an effective way to control the film morphology and to reduce the defect density. In this paper, formamidine acetate salt (FAAc) is introduced into the precursor solution as an effective additive to greatly improve the quality of perovskite films. With the addition of 5 mol% FAAc, the PSCs with a bis(4-phenyl)(2,4,6-trimethylphenyl)amine (PTAA) hole extraction layer demonstrate desirable performance in terms of the open-circuit voltage (1.04 V), the short-circuit current density (23.16 mA cm−2), the fill factor (close to 80%), the power conversion efficiency (18.90%), negligible hysteresis, and the device stability (up to 80 days). These results will provide a new avenue for fabricating commercial perovskite solar cells.
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TL;DR: The current achievements about the applications of polymers in solar cells are reviewed and analyzed and the benefits and challenges for practical application, and possible solutions are assessed.
Abstract: The emerging dye-sensitized solar cells, perovskite solar cells, and organic solar cells have been regarded as promising photovoltaic technologies. The device structures and components of these solar cells are imperative to the device’s efficiency and stability. Polymers can be used to adjust the device components and structures of these solar cells purposefully, due to their diversified properties. In dye-sensitized solar cells, polymers can be used as flexible substrates, pore- and film-forming agents of photoanode films, platinum-free counter electrodes, and the frameworks of quasi-solid-state electrolytes. In perovskite solar cells, polymers can be used as the additives to adjust the nucleation and crystallization processes in perovskite films. The polymers can also be used as hole transfer materials, electron transfer materials, and interface layer to enhance the carrier separation efficiency and reduce the recombination. In organic solar cells, polymers are often used as donor layers, buffer layers, and other polymer-based micro/nanostructures in binary or ternary devices to influence device performances. The current achievements about the applications of polymers in solar cells are reviewed and analyzed. In addition, the benefits of polymers for solar cells, the challenges for practical application, and possible solutions are also assessed.
137 citations
Cites background from "Additive engineering to improve the..."
...The diversified functional groups make it possible for the polymers to regulate the perovskite morphologies from bulk and interface aspects; the high carrier mobilities enable polymers acting as electron and hole transfer materials; the functional groups in polymers decide that they can be used as the interface layers to passivate defects, adjust the work function of the metal electrode, and improve the device performances [20,21]; the diversified structures and functional modification also equip polymers with various optical adsorption properties and variable electron mobility, being used as the photo-active layer or buffer layer in OPV [22,23]; The processability of polymer also make it possible to fabricate polymer-based micro/nanostructure devices....
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TL;DR: In this article, a review of different types of additive techniques applied in PSCs to enhance not only efficiency but also long-term stability is presented, taking into account the recently reported ISOS protocols, as well as the possible relation between shallow defect passivation, ion immobilization and device operational stability.
48 citations
TL;DR: In this article, the 1-methyl-3-propylimidazolium bromide (MPIB) additive was used to improve the power conversion efficiency of perovskite solar cells.
Abstract: During perovskite film preparation, the defects in the film are almost impossible to avoid because of the migration of the halide ions, which is detrimental to achieving a high-quality film. In general, the introduction of an additive is an effective strategy to control the film morphology and to reduce the defect density. Here, the representative and simplest ionic liquid, 1-methyl-3-propylimidazolium bromide (MPIB), is selected as an additive due to its high conductivity and lone-pair electrons in its cationic group. Remarkably, the addition of the MPIB additive into the perovskite film improves the power conversion efficiency (PCE) from 15.9% for the pristine device to 18.2%. With the help of characterization analysis by scanning electron microscopy, X-ray photoelectron spectroscopy, Fourier transform infrared spectroscopy, etc., two contributions of the MPIB additive are addressed: (1) the primary one is the passivation of the uncoordinated Pb2+ to reduce the defects in the perovskite film by the lone-pair electrons in its cationic group, and (2) the secondary one is beneficial to promote crystal growth to improve the film quality. Hence, this work provides an easy approach to achieve a high-performance perovskite solar cell via passivation of the uncoordinated Pb2+ in the perovskite film by the lone-pair electrons in the cationic group of the ionic liquid.
32 citations
TL;DR: In this paper, a comprehensive summary of the recent advances in developing stable and efficient planar perovskite solar cells (p-PSCs) is provided, focusing on adopting three main strategies, i.e., materials design, defect control and interfacial engineering, to enhance both stability and power conversion efficiency of p-PSC at the same time.
30 citations
References
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TL;DR: A sequential deposition method for the formation of the perovskite pigment within the porous metal oxide film that greatly increases the reproducibility of their performance and allows the fabrication of solid-state mesoscopic solar cells with unprecedented power conversion efficiencies and high stability.
Abstract: Following pioneering work, solution-processable organic-inorganic hybrid perovskites-such as CH3NH3PbX3 (X = Cl, Br, I)-have attracted attention as light-harvesting materials for mesoscopic solar cells. So far, the perovskite pigment has been deposited in a single step onto mesoporous metal oxide films using a mixture of PbX2 and CH3NH3X in a common solvent. However, the uncontrolled precipitation of the perovskite produces large morphological variations, resulting in a wide spread of photovoltaic performance in the resulting devices, which hampers the prospects for practical applications. Here we describe a sequential deposition method for the formation of the perovskite pigment within the porous metal oxide film. PbI2 is first introduced from solution into a nanoporous titanium dioxide film and subsequently transformed into the perovskite by exposing it to a solution of CH3NH3I. We find that the conversion occurs within the nanoporous host as soon as the two components come into contact, permitting much better control over the perovskite morphology than is possible with the previously employed route. Using this technique for the fabrication of solid-state mesoscopic solar cells greatly increases the reproducibility of their performance and allows us to achieve a power conversion efficiency of approximately 15 per cent (measured under standard AM1.5G test conditions on solar zenith angle, solar light intensity and cell temperature). This two-step method should provide new opportunities for the fabrication of solution-processed photovoltaic cells with unprecedented power conversion efficiencies and high stability equal to or even greater than those of today's best thin-film photovoltaic devices.
8,427 citations
TL;DR: An approach for depositing high-quality FAPbI3 films, involving FAP bI3 crystallization by the direct intramolecular exchange of dimethylsulfoxide (DMSO) molecules intercalated in PbI2 with formamidinium iodide is reported.
Abstract: The band gap of formamidinium lead iodide (FAPbI3) perovskites allows broader absorption of the solar spectrum relative to conventional methylammonium lead iodide (MAPbI3). Because the optoelectronic properties of perovskite films are closely related to film quality, deposition of dense and uniform films is crucial for fabricating high-performance perovskite solar cells (PSCs). We report an approach for depositing high-quality FAPbI3 films, involving FAPbI3 crystallization by the direct intramolecular exchange of dimethylsulfoxide (DMSO) molecules intercalated in PbI2 with formamidinium iodide. This process produces FAPbI3 films with (111)-preferred crystallographic orientation, large-grained dense microstructures, and flat surfaces without residual PbI2. Using films prepared by this technique, we fabricated FAPbI3-based PSCs with maximum power conversion efficiency greater than 20%.
5,458 citations
TL;DR: It is found that the diffusion lengths in CH3NH3PbI3 single crystals grown by a solution-growth method can exceed 175 micrometers under 1 sun (100 mW cm−2) illumination and exceed 3 millimeters under weak light for both electrons and holes.
Abstract: Long, balanced electron and hole diffusion lengths greater than 100 nanometers in the polycrystalline organolead trihalide compound CH3NH3PbI3 are critical for highly efficient perovskite solar cells. We found that the diffusion lengths in CH3NH3PbI3 single crystals grown by a solution-growth method can exceed 175 micrometers under 1 sun (100 mW cm(-2)) illumination and exceed 3 millimeters under weak light for both electrons and holes. The internal quantum efficiencies approach 100% in 3-millimeter-thick single-crystal perovskite solar cells under weak light. These long diffusion lengths result from greater carrier mobility, longer lifetime, and much smaller trap densities in the single crystals than in polycrystalline thin films. The long carrier diffusion lengths enabled the use of CH3NH3PbI3 in radiation sensing and energy harvesting through the gammavoltaic effect, with an efficiency of 3.9% measured with an intense cesium-137 source.
4,393 citations
TL;DR: It is found that the chemical and physical properties of these materials strongly depend on the preparation method, and the properties of the title hybrid materials with those of the "all-inorganic" CsSnI3 and CsPbI3 prepared using identical synthetic methods.
Abstract: A broad organic–inorganic series of hybrid metal iodide perovskites with the general formulation AMI3, where A is the methylammonium (CH3NH3+) or formamidinium (HC(NH2)2+) cation and M is Sn (1 and 2) or Pb (3 and 4) are reported. The compounds have been prepared through a variety of synthetic approaches, and the nature of the resulting materials is discussed in terms of their thermal stability and optical and electronic properties. We find that the chemical and physical properties of these materials strongly depend on the preparation method. Single crystal X-ray diffraction analysis of 1–4 classifies the compounds in the perovskite structural family. Structural phase transitions were observed and investigated by temperature-dependent single crystal X-ray diffraction in the 100–400 K range. The charge transport properties of the materials are discussed in conjunction with diffuse reflectance studies in the mid-IR region that display characteristic absorption features. Temperature-dependent studies show a ...
4,372 citations
TL;DR: A low-temperature vapor-assisted solution process is demonstrated to construct polycrystalline perovskite thin films with full surface coverage, small surface roughness, and grain size up to microscale, paving the way for high reproducibility of films and devices.
Abstract: Hybrid organic/inorganic perovskites (e.g., CH3NH3PbI3) as light absorbers are promising players in the field of third-generation photovoltaics. Here we demonstrate a low-temperature vapor-assisted solution process to construct polycrystalline perovskite thin films with full surface coverage, small surface roughness, and grain size up to microscale. Solar cells based on the as-prepared films achieve high power conversion efficiency of 12.1%, so far the highest efficiency based on CH3NH3PbI3 with the planar heterojunction configuration. This method provides a simple approach to perovskite film preparation and paves the way for high reproducibility of films and devices. The underlying kinetic and thermodynamic parameters regarding the perovskite film growth are discussed as well.
2,136 citations