Formamidinium Perovskite Deposition in Ambient Air Environment for Inverted p-i-n Solar Cells.

In order to move towards large-scale fabrication, perovskite solar cells need to detach themselves from strictly controlled environmental conditions and, to this end, fabrication in ambient air is highly desirable. Formamidinium iodide perovskite (FAPI) is one of the most promising perovskites but is also unstable at room temperature, which may make the ambient air deposition more difficult. Herein, we investigated different formulations of pure FAPI for the fabrication of perovskite solar cells (PSCs) in air. We found that formulations using a mixture of N,N-Dimethylformamide (DMF): N-methyl-2-pyrrolidone (NMP) and only dimethyl sulfoxide (DMSO) are suitable for the deposition in air. To fabricate inverted p-i-n solar cells, we tested different hole transporting layers (HTLs) and observed the effects on the wettability of the perovskite solution and on the performance. A self-assembly monolayer of 2PACz (2-(9H-Carbazol-9-yl)ethyl]phosphonic acid) was found to be the best option as a HTL, allowing us to achieve efficiencies >15% on both FTO and ITO.

Polymer-Assisted Single-Step Slot-Die Coating of Flexible Perovskite Solar Cells at Mild Temperature from Dimethyl Sulfoxide.

The industrialization of perovskite solar cells relies on solving intrinsic-to-material issues. To reach record efficiencies perovskite deposition needs to be finely adjusted by multi-step processes, in a humidity free glove-box environment and by means of hardly scalable techniques often associated with toxic solvents and anti-solvent dripping/bath. Herein, the use of polymeric material is proposed to deposit perovskite layers with easy processability. To the scope, a starch-polymer/perovskite composite is developed to suit slot-die coating technique requirement, allowing the deposition of hybrid halide perovskite material in a single straightforward step without the use of toxic solvents, and in uncontrolled humid environment (RH up to 70 %). The starch-polymer increases the viscosity of the perovskite precursor solutions and delays the perovskite crystallization that results in the formation of perovskite films at mild temperature (60 °C) with good morphology. These innovative inks enables the fabrication of flexible solar cells with p-i-n configuration featured by a power conversion efficiency higher than 3 %. . Overall, this approach can be exploited in the future to massively reduce perovskite manufacturing costs related to keeping the entire fabrication line at high-temperature and under nitrogen or dry conditions.

Photovoltaic characterization of di-branched organic sensitizers for DSSCs.

In this work, the data on the effect of peripheral functionalization of a series of triphenylamine based di-branched dyes used as sensitizers in dye-sensitized solar cells are presented. The effect of different alkyl functionalities on the donor moiety upon the optical and photovoltaics parameters have been investigated in dye-sensitized solar cells (DSSCs) using a 10-µm TiO2 active layer. The absorption spectra, output efficiency, and incident photon to conversion efficiency of the DSSCs have been collected. The data can be exploited for properly designing efficient, stable, and industrially viable dyes for third generation solar devices.

Improving the efficiency of copper-dye-sensitized solar cells by manipulating the electrolyte solution.

The use of a copper(i) dye, bearing a 2,9-dimesityl-1,10-phenanthroline and a 6,6'-dimethyl-2,2'-bipyridine-4,4'-dibenzoic acid, was investigated in DSSCs with various electrolyte solutions based on two different redox mediators, namely the common I-/I3- couple and an interesting copper electron shuttle. The experimental results provide evidence of the importance of the redox mediator concentration and the crucial role of additives such as 4-tert-butylpyridine and lithium bis(trifluoromethanesulfonyl)imide in the performance of sustainable "full-copper" DSSCs, consolidating the way to DSSCs with Earth-abundant components.

Towards efficient sustainable full-copper dye-sensitized solar cells.

Two new heteroleptic copper(i) sensitizers bearing 6,6'-dimethyl-2,2'-bipyridine-4,4'-dibenzoic acid, to anchor the dye on the titania surface, and a π-delocalized 2-(R-phenyl)-1H-phenanthro[9,10-d]imidazole (R = NPh2 or O-hexyl) ancillary ligand were prepared and well characterized. Their performance as dyes in DSSCs is quite similar to that of the related complex bearing 2,9-dimesityl-1,10-phenanthroline as an ancillary ligand, when using the common I-/I3- redox couple or homoleptic copper complexes as electron shuttles. The experimental results along with theoretical calculations confirm the great potential of full-copper DSSCs.

Preparation of N,N-dialkylcarbamato lanthanide complexes by extraction of lanthanide ions from aqueous solution into hydrocarbons.

Lanthanides are easily extracted as N,N-dibutylcarbamato complexes from aqueous solutions of their chlorides into heptane solutions of dibutylamine saturated with CO2. The products are recovered in high yields and are soluble in hydrocarbons. The derivatives [Ln(O2CNBu2)3]n [Ln = Nd (1), Eu (2), Tb (3)], [NH2Bu2]2[Ln4(CO3)(O2CNBu2)12] [Ln = Tb (4), Sm (5), Eu (6)], and [Sm4(CO3)(O2CNBu2)10], 7, have thus been obtained. The crystal and molecular structure of 4 has been solved; the samarium and europium complexes 5 and 6 were found to be isostructural. Mass spectra of the complexes 1-3, 4, and 7 (in MeCN/toluene) reveal that equilibria are present in solution. Compound 2 has been reacted in toluene with NHBz2 in the presence of CO2 affording [NH2Bz2][Eu(O2CNBz2)4], 8, through a ligand exchange process. By thermal treatment, 8 afforded [Eu(O2CNBz2)3]n, 9. With a similar procedure [Sm(O2CNBz2)3]n, 10, was obtained from 5. According to the photoluminescence study carried out on solid samples of 2, 4, 5, 7, and 8, the metal centered f-f transitions represent the only effective way to induce lanthanide luminescence in these complexes.

Mono- and dinuclear complexes of sulfones with the tetrachlorides of group 4.

The reactions of dialkyl sulfones [R(2)SO(2): R = Me, Et, Ph, R(2)=-(CH(2))(4)-] with the metal tetrachlorides of Group 4 [MCl(4): M = Ti, Zr, Hf] give different products mainly depending on the sulfone/M molar ratio. Compounds of formula [M(2)Cl(8)(R(2)SO(2))(2)][M = Ti, R(2)=-(CH(2))(4)-; M = Zr, R = Et, R = Ph] and [MCl(4)(R(2)SO(2))(2)](sulfone/M = 2)[M = Ti, R = Me; M = Zr, R = Me, R = Ph, R(2)=-(CH(2))(4)-; M = Hf, R = Me, R(2)=-(CH(2))(4)-] have been obtained. By X-ray diffraction methods the dinuclear titanium and zirconium adducts, [Ti(2)Cl(8)(mu-sulfolane-O,O')(2)] and [Zr(2)Cl(8)(mu-Ph(2)SO(2)-O,O')(2)] have been established to contain bridging sulfone and hexacoordinated metal centres, while the mononuclear zirconium complex [ZrCl(4)(Me(2)SO(2))(2)] has cis-monodentate sulfones in a slightly distorted octahedral geometry. The reaction between TiCl(4) and sulfolane (tetrahydrothiophene 1,1-dioxide) in SOCl(2) affords the 1:1 adduct independent of the sulfone/Ti molar ratio. Ligand-exchange and inter-conversion between mononuclear and dinuclear species have been observed by NMR, while the spectral features of the SO(2) moiety have been assigned by IR- and Raman spectroscopies.