Copper(I) dye-sensitized solar cells with [Co(bpy)3]2+/3+ electrolyte

The hierarchical assembly of DSCs containing a new heteroleptic copper(I) complex with a phosphonic acid anchoring ligand is described; it is shown that conventional I−/I3− electrolytes may be replaced by [Co(bpy)3]2+/3+ with no loss in performance

The number of matchings in random graphs

We study matchings on sparse random graphs by means of the cavity method. We first show how the method reproduces several known results about maximum and perfect matchings in regular and Erdos-Renyi random graphs. Our main new result is the computation of the entropy, i.e. the leading order of the logarithm of the number of solutions, of matchings with a given size. We derive both an algorithm to compute this entropy for an arbitrary graph with a girth that diverges in the large size limit, and an analytic result for the entropy in regular and Erdos-Renyi random graph ensembles.Comment: 17 pages, 6 figures, to be published in Journal of Statistical Mechanic

Solution processable direct bandgap copper-silver-bismuth iodide photovoltaics : compositional control of dimensionality and optoelectronic properties

Altres ajuts: SRR acknowledges the support from "laCaixa" Foundation (ID 100010434; LCF/BQ/PI20/11760024). Open access publishing facilitated by Monash University, as part of the Wiley - Monash University agreement via the Council of Australian University Librarians.The search for lead-free alternatives to lead-halide perovskite photovoltaic materials resulted in the discovery of copper(I)-silver(I)-bismuth(III) halides exhibiting promising properties for optoelectronic applications. The present work demonstrates a solution-based synthesis of uniform CuAgBiI thin films and scrutinizes the effects of x on the phase composition, dimensionality, optoelectronic properties, and photovoltaic performance. Formation of pure 3D CuAgBiI at x = 1, 2D CuAgBiI at x = 2, and a mix of the two at 1 < x < 2 is demonstrated. Despite lower structural dimensionality, CuAgBiI has broader optical absorption with a direct bandgap of 1.89 ± 0.05 eV, a valence band level at -5.25 eV, improved carrier lifetime, and higher recombination resistance as compared to CuAgBiI. These differences are mirrored in the power conversion efficiencies of the CuAgBiI and CuAgBiI solar cells under 1 sun of 1.01 ± 0.06% and 2.39 ± 0.05%, respectively. The latter value is the highest reported for this class of materials owing to the favorable film morphology provided by the hot-casting method. Future performance improvements might emerge from the optimization of the CuAgBiI layer thickness to match the carrier diffusion length of ≈40-50 nm. Nonencapsulated CuAgBiI solar cells display storage stability over 240 days

Naphthalene-imide Self-assembled Monolayers as a Surface Modification of ITO for Improved Thermal Stability of Perovskite Solar Cells [Dataset]

38 pages. -- 1. Thermal Properties. -- 2. Cyclic Voltammetry. -- 3. Optical Characterization. -- 4. Energy Level Diagram. -- 5. Self-Assembly. -- 6. Water Contact Angle Measurements. -- 7. XPS Measurements. -- 8. Perovskite Solar Cells. -- 9. Surface Recombination Velocity Measurements. -- 10. Drift-Diffusion Simulations. -- 11. Shelf-Life Stability. -- 12. Synthesis. -- 12.1. Naphthalene monoimides 2a-2d. -- 12.2. Naphthalene diimides 3a-3d. -- 13. ReferencesElectron-transport-layer-free (ETL-free) perovskite solar cells (PSCs) show great promise for commercialization due to their simple design and ease of fabrication. However, the interface between the transparent conductive oxides such as indium-doped tin oxide (ITO) and the perovskite is not optimal due to differences in their work functions, surface defects, and wettability of the substrates. Surface modification of ITO through self-assembled monolayers (SAMs) to get ITO/SAM charge selective layers has shown great improvement in device performance in recent years, but little emphasis has been put on the stability of these devices. Here, we address this gap by introducing a series of newly synthesized naphthalene-imide derivatives which self-assemble at the interface between ITO and the perovskite interface and study their impact on the thermal stability of triple-cation PSCs. The chemical and thermal stabilities of the naphthalene-imide SAMs help improve the thermal stability of the devices, reaching T80 lifetimes exceeding 800 h for devices containing a pyridine-functionalized naphthalene diimide carboxylic acid at 85 °C in air. In addition, all SAMs improve the stabilized power output of the devices with respect to ITO-only reference devices. Drift-diffusion simulations reveal the strong influence of the ITO work function on the efficiency in ETL-free devices, and a work function reduction of 0.2 eV could improve efficiencies by over 30%. The functional diversity of naphthalene imides coupled with the ease of SAM deposition opens a pathway for stable, high-performing PSCs based on electron selective monolayers.Peer reviewe

Heteroleptic copper(I) sensitizers with one versus two hole-transporting units in functionalized 2,9-dimethyl-1,10-phenanthroline ancillary ligands

A series of homoleptic [Cu(L)2][PF6] complexes in which L is a 2,9-dimethyl-1,10-phenanthroline fused at the 5,6-positions with a 2′-functionalized imidazole (ligands 1–4), or substituted at the 4,7-positions with electron-donating 4-(diphenylamino)phenyl groups (ligand 5) is described; the imidazole 2′-functionality in 1 is 4-bromophenyl, in 2 is 4-(diphenylamino)phenyl, in 3 is 4-(bis(4-n-butoxy)phenylamino)phenyl, and in 4 is 4-(carbazol-9-yl)phenyl. The copper complexes were characterized by mass spectrometry, NMR and absorption spectroscopies and cyclic voltammetry; the single crystal structure of ligand 4 has been determined. Compared to the solution absorption spectra of [Cu(1)2][PF6], [Cu(2)2][PF6], [Cu(3)2][PF6] and [Cu(4)2][PF6], that of [Cu(5)2][PF6] shows increased absorbance at wavelengths >375 nm. An on-surface strategy was used to assemble heteroleptic [Cu(6)(L)]+ dyes on TiO2 electrodes where 6 is ((6,6′-dimethyl-[2,2′-bipyridine]-4,4′-diyl)bis(4,1-phenylene))bis(phosphonic acid); solid-state absorption spectra confirmed enhanced light-harvesting between 375 and 600 nm for [Cu(6)(5)]+ with respect to [Cu(6)(1)]+, [Cu(6)(2)]+, [Cu(6)(3)]+ and [Cu(6)(4)]+. Comparison of the performances of dye-sensitized solar cells (DSCs) containing [Cu(6)(2)]+, [Cu(6)(3)]+ and [Cu(6)(4)]+ with those with [Cu(6)(1)]+ indicate only a marginal influence of the diphenylamine or carbazole hole-transporting domains in 5,6-substituted phenanthroline dyes. The introduction of the 4-(diphenylamino)phenyl hole-transporting units in the 4- and 7-positions of the phen unit in 5 proves to be beneficial, with DSCs containing [Cu(6)(5)]+ performing better than those with the other four dyes; duplicate DSCs were tested for each dye to validate the results. While the values of the maximum external quantum efficiencies (EQEmax) for [Cu(6)(1)]+ and [Cu(6)(4)]+ are greater than for [Cu(6)(5)]+, the extension of the EQE spectrum for [Cu(6)(5)]+ to longer wavelengths results in higher short-circuit current densities (JSC) compared to DSCs with [Cu(6)(1)]+, [Cu(6)(2)]+, [Cu(6)(3)]+ and [Cu(6)(4)]+

Hole-transport functionalized copper(I) dye sensitized solar cells

Ligands containing first and second generation hole-transport triphenylamino-dendrons have been evaluated as ancillary ligands in copper(I) DSCs yielding an optimal efficiency of 3.77% in unmasked cells. The effects of masking the DSCs on measured parameters are discussed

Improving performance of copper(I)-based dye sensitized solar cells through I3–/I– electrolyte manipulation

The performances of dye-sensitized solar cells (DSSCs) containing a heteroleptic bis(diimine)copper(I) dye and an I 3 /I liquid electrolyte have been investigated as a function of the electrolyte composition. Starting from a standard electrolyte with LiI (0.1 M), I2 (0.05 M), 1-butyl-3-methylimidazolium (BMII) ionic liquid (0.6 M), 1-methylimidazole additive (0.5 M) in 3-methoxypropionitrile (MPN), a series of ten electrolytes was initially screened; the solvent, additives, concentration of I2, and sources (LiI and/or BMII) and concentrations of I were varied. The highest short-circuit current densities (JSC 1⁄4 7.85 and 7.60 mA cm 2) and photoconversion efficiencies (h 1⁄4 2.64 and 2.70% relative to 6.56 and 6.11% for two N719 references) were observed for DSSCs with an electrolyte comprising I2 (0.03 M), BMII (0.6 M), 4- tert-butylpyridine (TBP, 0.4 M) and guanidinium thiocyanate (GNCS, 0.1 M) in MPN solvent; no LiI was added. This composition was further optimized by varying the amounts of TBP and GNCS. A low con- centration of I2 (0.015 M) is optimal. The presence or absence of GNCS has little effect on overall DSSC performance, but increasing the concentration of TBP is detrimental to DSSC performance, and an absence of TBP is beneficial. Open-circuit voltage decay (OCVD) measurements confirm that the addition of GNCS and/or TBP reduces recombination rates at the TiO2-dye interface. The best DSC parameters obtained for the copper(I)-based dye were JSC 1⁄4 7.80 mA cm 2, open-circuit voltage (VOC) 1⁄4 501 mV and h 1⁄4 2.76% (relative to 6.72% for N719)

Improving the photoresponse of copper(I) dyes in dye-sensitized solar cells by tuning ancillary and anchoring ligand modules

The syntheses of five homoleptic copper(I) complexes [CuL2][PF6] are described in which L is a 4,4′-di(4-bromophenyl)-6,6′-dialkyl-2,2′-bipyridine ligand (compounds 1–4 with methyl, nbutyl, isobutyl and hexyl substituents, respectively) or 4,4′-di(4-bromophenyl)-6,6′-diphenyl-2,2′-bipyridine (5). The new ligands 2–5 and copper(I) complexes [CuL2][PF6] (L = 1–5) have been fully characterized. The single crystal structures of 2{[Cu(1)2][PF6]}·3Me2CO, [Cu(2)2][PF6], 2{[Cu(3)2][PF6]}·Et2O and [Cu(5)2][PF6]·CH2Cl2 have been determined. The first three structures show similar distorted tetrahedral environments for the Cu+ ions with angles between the least squares planes of the bpy domains of 85.6, 86.4 and 82.9°, respectively; in contrast, the Cu+ ion in [Cu(5)2][PF6]·CH2Cl2 is in a flattened coordinate environment due to intra-cation face-to-face π-interactions. The solution absorption spectra of the complexes with ligands 1–4 are virtually identical with an MLCT band with values of λmax = 481–488 nm. In contrast, the absorption spectrum of [Cu(5)2][PF6] shows two broad bands in the visible region. Cyclic voltammetric data show that oxidation of the copper(I) centre occurs at a more positive potential in [Cu(2)2][PF6], [Cu(3)2][PF6] and [Cu(4)2][PF6] than in [Cu(1)2][PF6] or [Cu(5)2][PF6] with the latter being oxidized at the lowest potential. The complexes have been used to prepare dye-sensitized solar cells (DSCs) incorporating heteroleptic dyes of type [Cu(L)(Lanchor)]+ where L is 1–5 and Lanchor is a 6,6′-dimethyl-2,2′-bipyridine functionalized in the 4- and 4′-positions with phosphonic acid groups with (Lanchor = 7) and without (Lanchor = 6) a spacer between the metal-binding and anchoring domains. The presence of the spacer results in enhanced performances of the dyes, and the highest energy conversion efficiencies are observed for the dyes [Cu(3)(7)]+ (η = 2.43% compared to 5.96% for standard dye N719) and [Cu(5)(7)]+ (η = 2.89% compared to 5.96% for N719). Measurements taken periodically over the course of a week indicate that the cells undergo a ripening process (most clearly seen for [Cu(5)(6)]+ and [Cu(5)(7)]+) before their optimum performances are achieved. IPCE (EQE) data are presented and confirm that, although the photo-to-current conversions are promising (37–49% for λmax ≈ 480 nm), the copper(I) dyes do not realize the broad spectral response exhibited by N719

Batch Proofs of Partial Knowledge

We present a practical attack on soundness in Peng and Bao’s ‘batch zero-knowledge proof and verification’ protocol for proving knowledge and equality of one-out-of-n pairs of discrete logarithms. Fixing the protocol seems to require a commitment scheme with a nonstandard, mercurial-esque binding property: the prover commits to just n − 1 values, but later opens the commitment to n values without revealing which one out of the n values was not in the original commitment. With this requirement as a motivator, we propose and formally define all-but-k commitment schemes, and give a concrete construction based on polynomial commitments. We use the special case of “all-but-one ” commitments to fix the above zero-knowledge protocol and then we describe a variant of the protocol that uses the more general all-but-k commitments to implement a batch zero-knowledge proof of knowledge and equality of k-out-of-n pairs of discrete logarithms, for arbitrary (public) k ∈ [1, n]. This latter protocol is asymptotically efficient, and it naturally yields batch “OR ” proofs (one-out-of-n) and batch “AND ” proofs (n-out-of-n) as two special cases; for all intermediate 1 &lt; k &lt; n, it is entirely novel

Efficient authentication from hard learning problems

Abstract. We construct efficient authentication protocols and messageauthentication codes (MACs) whose security can be reduced to the learning parity with noise (LPN) problem. Despite a large body of work – starting with the HB protocol of Hopper and Blum in 2001 – until now it was not even known how to construct an efficient authentication protocol from LPN which is secure against man-in-the-middle (MIM) attacks. A MAC implies such a (two-round) protocol.