In the scenario of the new emerging photovoltaics, kesterites play a lead role in the thin-film solar cell technologies. This class of compounds, mainly represented by the pure-sulfide form Cu2ZnSnS4 (CZTS) and the sulfo-selenide form Cu2ZnSn(S,Se)4 (CZTSSe), shows unique characteristics and stands as a promising p-type absorber material thanks to its high absorption coefficient, high cost-effectiveness and low toxicity. However, CdS is commonly used as the n-type partner (buffer layer) in kesterite solar cells but, beyond its toxicity, it has a nonoptimal band alignment with kesterites and exhibits parasitic absorption at low wavelengths due to its bandgap. Several efforts have been made in the last decade, to replace CdS with a suitable, Cd-free, both environmentally and economically sustainable buffer layer, and many times with successful results allowing not only to equal, but also to overcome in few cases the performances of the corresponding CdS-based reference devices. Zn1-xSnxO for instance leads to higher efficiencies than CdS when coupled with pure-sulfide CZTS, while Zn(O,S) seems to couple better with CZTSSe. TiO2 has been also considered as suitable buffer layer for kesterites and, in the last few years, several works have been reported both theoretical and experimental, showing very promising results. In this review we summarize the efforts and the improvements recorded by the scientific community working on this topic in the last ten years, with the aim to supply a landmark useful to design future experiments in a more efficient way and to push forward the related research activities, in order to fully overcome CdS limitations and to promote thin-film kesterite devices to higher performances.
In the scenario of the new emerging photovoltaics, kesterites play a lead role in the thin-film solar cell technologies. This class of compounds, mainly represented by the pure-sulfide form Cu2ZnSnS4 (CZTS) and the sulfo-selenide form Cu2ZnSn(S,Se)4 (CZTSSe), shows unique characteristics and stands as a promising p-type absorber material thanks to its high absorption coefficient, high cost-effectiveness and low toxicity. However, CdS is commonly used as the n-type partner (buffer layer) in kesterite solar cells but, beyond its toxicity, it has a nonoptimal band alignment with kesterites and exhibits parasitic absorption at low wavelengths due to its bandgap. Several efforts have been made in the last decade, to replace CdS with a suitable, Cd-free, both environmentally and economically sustainable buffer layer, and many times with successful results allowing not only to equal, but also to overcome in few cases the performances of the corresponding CdS-based reference devices. Zn1-xSnxO for instance leads to higher efficiencies than CdS when coupled with pure-sulfide CZTS, while Zn(O,S) seems to couple better with CZTSSe. TiO2 has been also considered as suitable buffer layer for kesterites and, in the last few years, several works have been reported both theoretical and experimental, showing very promising results. In this review we summarize the efforts and the improvements recorded by the scientific community working on this topic in the last ten years, with the aim to supply a landmark useful to design future experiments in a more efficient way and to push forward the related research activities, in order to fully overcome CdS limitations and to promote thin-film kesterite devices to higher performances.
A [copper(I)pyridine-containing ligand]-catalyzed reaction between 2-vinylindoles and diazo esters is described. The reaction allows for the synthesis of a series of 2-vinylcyclopropa[b]indolines with excellent levels of regio- and sterocontrol under mild conditions.
Pure sulfide kesterite (Cu2ZnSnS4) is one of the most promising emerging photovoltaic technologies thanks to its excellent absorption coefficient, cost-effectiveness, and environmental sustainability. However, record efficiencies are not exceeding 11% due to several issues, such as absorber defects or a nonoptimal band alignment with the toxic but conventionally used CdS buffer layer. To get rid of it, several efforts have been made in the past few years. Among recent theoretical works, TiO2 has been suggested as a suitable buffer layer due to its optical and electrical properties, giving extremely promising results in device simulation. However, there are few experimental examples combining TiO2 with kesterite, and they generally show very modest performances. In this Letter, we report on the preliminary and promising results of our experimental procedure for the production of Cd-free kesterite photovoltaic devices featuring ALD-TiO2 as a buffer layer, leading to efficiencies comparable with our CZTS/CdS reference devices.
The Ag(i) complexes of pyridine-containing ligands with an active pendant arm are new catalysts for an old reaction: the nitroaldol condensation. When the substrates are 2-alkynylarylaldehydes, a smart cascade cycloisomerisation process can occur.
Defects are inherent in transition metal dichalcogenides and significantly affect their chemical and physical properties. In this study, surface defect electrochemical nanopatterning is proposed as a promising method to tune in a controlled manner the electronic and functional properties of defective MoS₂ thin films. Using parallel electrochemical nanolithography, MoS₂ thin films are patterned, creating sulphur vacancy-rich active zones alternated with defect-free regions over a centimetre scale area, with sub-micrometre spatial resolution. The patterned films display tailored optical and electronic properties due to the formation of sulphur vacancy-rich areas. Moreover, the effectiveness of defect nanopatterning in tuning functional properties is demonstrated by studying the electrocatalytic activity for the hydrogen evolution reaction.
We report herein the first example of the silver triflate catalysed synthesis of 1,3‐dicarbo‐substituted isochromene derivatives starting from 2‐alkynyl(hetero)arylaldehydes and enolizable ketones. The reaction proceeds in a cascade fashion under mild heating with complete regioselectivity and moderate‐to‐good yields. In some cases, the reaction gives unexpected homodimeric products. Two competitive mechanistic paths for the formation of the desired isochromene derivatives and the homodimeric products are described.
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