In this study, a series of donor–acceptor–donor (D‐A‐D) type small molecules based on the fluorene and diphenylethenyl enamine units, which are distinguished by different acceptors, as ...holetransporting materials (HTMs) for perovskite solar cells is presented. The incorporation of the malononitrile acceptor units is found to be beneficial for not only carrier transportation but also defects passivation via Pb–N interactions. The highest power conversion efficiency of over 22% is achieved on cells based on V1359, which is higher than that of spiro‐OMeTAD under identical conditions. This st shows that HTMs prepared via simplified synthetic routes are not only a low‐cost alternative to spiro‐OMeTAD but also outperform in efficiency and stability state‐of‐art materials obtained via expensive cross‐coupling methods.
Engineering of donor–acceptor–donor functional enamine hole transporting materials is presented leading to the low‐cost hole transporting materia V1359 to reach power conversion efficiency over 22% in perovskite solar cells with excellent stability surpassing the reference spiro‐OMeTAD due to the incorporation of the malononitrile acceptor units that passivate the surficial perovskite defects via Pb–N interactions.
The development of advanced anodes for low-cost room temperature sodium-ion batteries (SIBs) with high cycling stability is of great significance. Silicon clathrates are promising intercalation ...anodes due to their cage-like frameworks. It is predicted that the open cages can easily accommodate alkali ions with negligible volume changes. However, the complicated surface structure and chemical reactions make it challenging to understand the electrochemical performance of clathrate anodes in SIBs. In this paper, we evaluated the performance of type II clathrate anodes in SIBs. A slightly elevated testing temperature (45°C) is shown to improve the cell capacity and rate performance due to the improved ionic conductivity. However, side reactions on the solid electrolyte interface (SEI) and loss of active material during the first sodiation process contribute to the low Coulombic efficiency during the first cycle. Analysis is supported by electrode morphology, elemental mapping, and X-ray photoelectron spectroscopy (XPS) on the clathrate electrodes at different electrochemical states. Na+ ion transport behavior between clathrate cages and surface in terms of migration barriers was also computed to explain the positive effect of higher cell testing temperature, and the low Coulombic efficiency of the first cycle.
Abstract Room‐temperature sodium‐sulfur (RT Na−S) batteries, noted for their low material costs and high energy density, are emerging as a promising alternative to lithium‐ion batteries (LIBs) in ...various applications including power grids and standalone renewable energy systems. These batteries are commonly assembled with glass fiber membranes, which face significant challenges like the dissolution of polysulfides, sluggish sulfur conversion kinetics, and the growth of Na dendrites. Here, we develop an amorphous two‐dimensional (2D) iron tin oxide (A‐FeSnO x ) nanosheet with hierarchical vacancies, including abundant oxygen vacancies (O v s) and nano‐sized perforations, that can be assembled into a multifunctional layer overlaying commercial separators for RT Na−S batteries. The O v s offer strong adsorption and abundant catalytic sites for polysulfides, while the defect concentration is finely tuned to elucidate the polysulfides conversion mechanisms. The nano‐sized perforations aid in regulating Na ions transport, resulting in uniform Na deposition. Moreover, the strategic addition of trace amounts of Ti 3 C 2 (MXene) forms an amorphous/crystalline (A/C) interface that significantly improves the mechanical properties of the separator and suppresses dendrite growth. As a result, the task‐specific layer achieves ultra‐light (~0.1 mg cm −2 ), ultra‐thin (~200 nm), and ultra‐robust (modulus=4.9 GPa) characteristics. Consequently, the RT Na−S battery maintained a high capacity of 610.3 mAh g −1 and an average Coulombic efficiency of 99.9 % after 400 cycles at 0.5 C.
Room-temperature sodium-sulfur (RT Na-S) batteries, noted for their low material costs and high energy density, are emerging as a promising alternative to LIBs in various applications including power ...grids and standalone renewable energy systems. These batteries are commonly assembled with glass fiber membranes, which face significant challenges like the dissolution of polysulfides, sluggish sulfur conversion kinetics, and the dendrites growth. Here, we develop an amorphous FeSnOx nanosheet with hierarchical vacancies, including abundant oxygen vacancies (Ovs) and nano-sized perforations, that can be assembled into a multifunctional layer overlaying commercial separators for RT Na-S batteries. The Ovs offer strong adsorption and abundant catalytic sites for polysulfides, while the defect concentration is finely tuned to elucidate the polysulfides conversion mechanisms. The nano-sized perforations aid in regulating Na ions transport, resulting in uniform Na deposition. Moreover, the strategic addition of trace amounts of Ti3C2 forms an amorphous/crystalline interface that significantly improves the mechanical properties of the separator and suppresses dendrite growth. As a result, the task-specific layer achieves ultra-light (~0.1mg cm-2), ultra-thin (~200nm), and ultra-robust (modulus = 4.9GPa) characteristics. Consequently, the RT Na-S battery maintained a high capacity of 610.3mAh g-1 and an average Coulombic efficiency of 99.9% after 400 cycles at 0.5C.
The replacement of a small amount of organic cations with bulkier organic spacer cations in the perovskite precursor solution to form a 2D perovskite passivation agent (2D‐PPA) in 3D perovskite thin ...films has recently become a promising strategy for developing perovskite solar cells (PSCs) with long‐term stability and high efficiency. However, the long, bulky organic cations often form a barrier, hindering charge transport. Herein, for the first time, 2D‐PPA engineering based on wide‐bandgap (≈1.68 eV) perovskites are reported. Pentafluorophenethylammonium (F5PEA+) is introduced to partially replace phenylethylammonium (PEA+) as the 2D‐PPA, forming a strong noncovalent interaction between the two bulky cations. The charge transport across and within the planes of pure 2D perovskites, based on mixed ammoniums, increases by a factor of five and three compared with that of mono‐cation 2D perovskites, respectively. The perovskite films based on mixed‐ammonium (F5PEA+‐PEA+) 2D‐PPA exhibit similar surface morphology and crystal structure, but longer carrier lifetime, lower exciton binding energy, less trap density and higher conductivity, in comparison with those using mono‐cation (PEA+) 2D‐PPA. The performance of PSCs based on mixed‐cation 2D‐PPA is enhanced from 19.58% to 21.10% along with improved stability, which is the highest performance for reported wide‐bandgap PSCs.
The introduction of F5PEA+ to partially replace PEA+ as the 2D perovskite passivation agent, with a strong noncovalent interaction between the two bulky cations and enhanced charge transport, is reported to improve the performance (from 19.58% to 21.10%) and stability of the corresponding wide‐bandgap perovskite solar cells.
Cover Image Xiao, Chuanxiao; Hacke, Peter; Johnston, Steve ...
Progress in photovoltaics,
September 2020, Volume:
28, Issue:
9
Journal Article
Peer reviewed
The cover image is based on the Research Article Failure analysis of field‐failed bypass diodes by Chuanxiao Xiao et al., https://doi.org/10.1002/pip.3297.
Perovskite/silicon tandems offer a promising pathway to increase the efficiency beyond the Auger limit of silicon at minimal additional cost. However, it is challenging to accommodate the ...solution-processed perovskite without flattening or reducing pyramidal texture of silicon subcells. Herein, we report the first monolithic perovskite/silicon tandem featuring an industrially applicable front-side-nanostructured black silicon with a tunnel oxide passivated contact (TOPCon). The TOPCon together with the surface reconstruction of black silicon contributes to the high-level surface passivation without sacrificing the broadband light trapping. Additionally, the reconstructed nanotexture significantly facilitates the wetting of perovskite and acts as a nanoconfining scaffold to guide the vertical growth of perovskite. The resulting tandem yields a certified efficiency of 28.2%, representing one of the highest efficiencies reported on either perovskite/TOPCon or double-side-textured perovskite/silicon tandems.
Display omitted
•Efficient perovskite/Si tandem solar cells based on nanotextured b-Si and TOPCon•The surface reconstruction balances the passivation and light trapping of b-Si•The b-Si guides the vertical growth of perovskite through nanoconfinement effect•The perovskite on b-Si exhibits the reduced strain and improved stability
Most reported monolithic perovskite/silicon tandems feature bottom cells with polished surfaces to be compatible with the solution-based perovskite fabrication or with pyramid structures to be compatible with the industrial-standard textured silicon. The former suffers from high costs and limited light trapping, whereas the latter brings new difficulties for achieving high-quality perovskite films. Here, we report the first perovskite/silicon tandem featuring an industry-relevant black silicon with tunnel oxide passivated contacts. The nanotextured black silicon is surface reconstructed to improve the passivation without sacrificing the light trapping. The reconstructed black silicon not only provides a wetting surface for perovskite deposition but also serves as a nanoconfining scaffold to guide the vertical growth of perovskite and to alleviate the film strains, simultaneously improving the tandem efficiency and stability.
The black silicon passivated by tunnel oxide provides a promising strategy to realize efficient perovskite/silicon tandem solar cells. The surface reconstruction of the black silicon is employed to achieve an excellent trade-off between the high-level surface passivation and the broadband light trapping. The resulted nanotexture significantly facilitates the wetting of perovskite and acts as a nanoconfining scaffold to guide the vertical growth of perovskite with reduced film strains, simultaneously improving the efficiency and stability of the perovskite/silicon tandem devices.
PDF
