Atomic layer deposition of NiO applied in a monolithic perovskite/PERC tandem cell

Monolithic perovskite/silicon tandem photovoltaics have fueled major research efforts as well as gaining rapid industrial interest. So far, most of the literature has focused on the use of currently more expensive silicon heterojunction bottom cell technology. This work demonstrates a perovskite/silicon tandem solar cell based on the industrially dominant passivated emitter and rear cell (PERC) technology. In detail, we investigate a tunnel recombination junction (TRJ) consisting of ITO/NiO/2-(9H-carbazol-9-yl)ethyl] phosphonic acid (2PACz) and compare it with an ITO/2PACz TRJ. Specifically, the NiO layer is deposited by atomic layer deposition (ALD). Although ITO/2PACz-based tandem devices can reach more than 24% conversion efficiency, we observe that they suffer from a large spread in photovoltaic parameters due to electrical shunts in the perovskite top cell, caused by the inhomogeneity of the 2PACz layer on ITO. Instead, when ALD NiO is sandwiched between 2PACz and ITO, the surface coverage of 2PACz improves and the yield of the devices, in terms of all device parameters, also improves, i.e., the standard deviation decreases from 4.6% with ITO/2PACz to 2.0% with ITO/NiO/2PACz. In conclusion, thanks to the presence of NiO, the TRJ consisting of ITO/NiO/2PACz leads to a 23.7% efficient tandem device with narrow device efficiency distribution

Preparation of a 6a-substituted optically pure steroid with thiophene as the A ring via asymmetric induction. A circular dichroism study

A number of asymmetrically induced cyclization reactions are described, furnishing specifically substituted steroid-like systems with thiophene as the A ring. Ring closure of achiral compounds gives two enantiomeric trans-anti-fused products, containing three chiral carbon atoms each. The presence of a nonepimerizable chirality in the cyclization precursor favors production of one ring-closed diastereomer over the other. A comparable example of an in vivo ring closure is found in the conversion of 2,3-epoxysqualene to various steroids. A chiral center far removed from the cyclization initiator also influences the stereochemical outcome of such cyclizations. A deuterium at pro-C-6 (steroid numbering) causes no measurable asymmetrically induced ring closure because of the deuterium's comparable size to a hydrogen atom. A methyl group at pro-C-6, however, will cause ring closure to proceed in 97% yield to a 6a-substituted steroid. A 100% asymmetrically induced ring closure in favor of the 6a-substituted products is brought about by a t-Bu group. Aforementioned stereospecificities are believed to stem from 1,3-diaxial interactions between the substituent at the chiral carbon atom and the pro-C-8 and pro-C-10 hydrogen atoms. This gives rise to a model description of the ring closure in terms of "precoiling". The ring closure of the optically pure tert-butyl-substituted alkene gives an optically pure steroid, since the reaction proceeds with 100% asymmetric induction. Hereby, a significant yield increase is observed (50% --+ 80%). The absolute configurations of the precursors and the cyclized products are determined by circular dichroism

Preparation of a 6a-substituted optically pure steroid with thiophene as the A ring via asymmetric induction. A circular dichroism study

A number of asymmetrically induced cyclization reactions are described, furnishing specifically substituted steroid-like systems with thiophene as the A ring. Ring closure of achiral compounds gives two enantiomeric trans-anti-fused products, containing three chiral carbon atoms each. The presence of a nonepimerizable chirality in the cyclization precursor favors production of one ring-closed diastereomer over the other. A comparable example of an in vivo ring closure is found in the conversion of 2,3-epoxysqualene to various steroids. A chiral center far removed from the cyclization initiator also influences the stereochemical outcome of such cyclizations. A deuterium at pro-C-6 (steroid numbering) causes no measurable asymmetrically induced ring closure because of the deuterium's comparable size to a hydrogen atom. A methyl group at pro-C-6, however, will cause ring closure to proceed in 97% yield to a 6a-substituted steroid. A 100% asymmetrically induced ring closure in favor of the 6a-substituted products is brought about by a t-Bu group. Aforementioned stereospecificities are believed to stem from 1,3-diaxial interactions between the substituent at the chiral carbon atom and the pro-C-8 and pro-C-10 hydrogen atoms. This gives rise to a model description of the ring closure in terms of "precoiling". The ring closure of the optically pure tert-butyl-substituted alkene gives an optically pure steroid, since the reaction proceeds with 100% asymmetric induction. Hereby, a significant yield increase is observed (50% --+ 80%). The absolute configurations of the precursors and the cyclized products are determined by circular dichroism

Asymmetric induction in the synthesis of thiophene-containing steroidlike molecules via olefinic cyclization. Precoiling as model description for the stereochemical course of the reaction

No abstract

The synthesis of bis(4-methyl-3-pentenyl)thiophenes

All possible isomers of title compounds 5a-8a have been prepared. All the routes presented have involved Wittig olefination of dicarbaldehydes 5c-8c. Synthetic aspects as regards the relevant intermediates are discussed

Low-temperature atomic layer deposition of MoOx for silicon heterojunction solar cells

The preparation of high-quality molybdenum oxide (MoOx) is demonstrated by plasma-enhanced atomic layer deposition (ALD) at substrate temperatures down to 50 °C. The films are amorphous, slightly substoichiometric with respect to MoO3, and free of other elements apart from hydrogen (&11 at%). The films have a high transparency in the visible region and their compatibility with a-Si:H passivation schemes is demonstrated. It is discussed that these aspects, in conjunction with the low processing temperature and the ability to deposit very thin conformal films, make this ALD process promising for the future application of MoOx in hole-selective contacts for silicon heterojunction solar cells

Low-temperature atomic layer deposition of MoOx for silicon heterojunction solar cells

The preparation of high-quality molybdenum oxide (MoOx) is demonstrated by plasma-enhanced atomic layer deposition (ALD) at substrate temperatures down to 50 °C. The films are amorphous, slightly substoichiometric with respect to MoO3, and free of other elements apart from hydrogen (&11 at%). The films have a high transparency in the visible region and their compatibility with a-Si:H passivation schemes is demonstrated. It is discussed that these aspects, in conjunction with the low processing temperature and the ability to deposit very thin conformal films, make this ALD process promising for the future application of MoOx in hole-selective contacts for silicon heterojunction solar cells

Asymmetric induction in the synthesis of thiophene-containing steroidlike molecules via olefinic cyclization. 2. Evidence for precoiling as model description for the cyclization

No abstract