3 ms·

New solar cell material achieves almost 100% efficiency

2 points by nickb 18y ago

DaniFong 18y ago
Damnit, journalism. How on earth did they get this: "Researchers at Ohio State University have accidentally discovered a new solar cell material capable of absorbing all of the sun's visible light energy. The material is comprised of a hybrid of plastics, molybdenum and titanium. The team discovered it not only fluoresces (as most solar cells do), but also phosphoresces. Electrons in a phosphorescent state remain at a place where they can be "siphoned off" as electricity over 7 million times longer than those generated in a fluorescent state. This combination of materials also utilizes the entire visible spectrum of light energy, translating into a theoretical potential of almost 100% efficiency. Commercial products are still years away, but this foundational work may well pave the way for a truly renewable form of clean, global energy." From this: "Oligothiophenes incorporating MM quadruple bonds have been prepared from the reactions between Mo2(TiPB)4 (TiPB = 2,4,6-triisopropyl benzoate) and 3′,4′-dihexyl-2,2′-:5′,2″-terthiophene-5,5″-dicarboxylic acid. The oligomers of empirical formula Mo2(TiPB)2(O2C(Th)-C4(n-hexyl)2S-(Th)CO2) are soluble in THF and form thin films with spin-coating (Th = thiophene). The reactions between Mo2(TiPB)4 and 2-thienylcarboxylic acid (Th-H), 2,2′-bithiophene-5-carboxylic acid (BTh-H), and (2,2′:5′,2″-terthiophene)-5-carboxylic acid (TTh-H) yield compounds of formula trans-Mo2(TiPB)2L2, where L = Th, BTh, and TTh (the corresponding thienylcarboxylate), and these compounds are considered as models for the aforementioned oligomers. In all cases, the thienyl groups are substituted or coupled at the 2,5 positions. Based on the x-ray analysis, the molecular structure of trans-Mo2(TiPB)2(BTh)2 reveals an extended Lπ-M2δ-Lπ conjugation. Calculations of the electronic structures on model compounds, in which the TiPB are substituted by formate ligands, reveal that the HOMO is mainly attributed to the M2δ orbital, which is stabilized by back-bonding to one of the thienylcarboxylate π * combinations, and the LUMO is an in-phase combination of the thienylcarboxylate π * orbitals. The compounds and the oligomers are intensely colored due to M2δ–thienyl carboxylate π * charge transfer transitions that fall in the visible region of the spectrum. For the molybdenum complexes and their oligomers, the photophysical properties have been studied by steady-state absorption spectroscopy and emission spectroscopy, together with time-resolved emission and transient absorption for the determination of relaxation dynamics. Remarkably, THF solutions the molybdenum complexes show room-temperature dual emission, fluorescence and phosphorescence, originating mainly from 1MLCT and 3MM(δδ* ) states, respectively. With increasing number of thienyl rings from 1 to 3, the observed lifetimes of the 1MLCT state increase from 4 to 12 ps, while the phosphorescence lifetimes are ≈80 μs. The oligomers show similar photophysical properties as the corresponding monomers in THF but have notably longer-lived triplet states, ≈200 μs in thin films. These results, when compared with metallated oligothiophenes of the later transition elements, reveal that M2δ–thienyl π conjugation leads to a very small energy gap between the1MLCT and 3MLCT states of <0.6 eV." http://www.pnas.org/content/105/40/15247.short http://www.pnas.org/content/105/40/15247.short The discovery of phosphorescent dual emission is a striking and important one, but there are dozens of hurdles still to create a solar cell, any one of which might be a nail in the coffin for the material. For example, just because some of the electrons end up in a triplet state doesn't mean all of them will: they've measured the singlet states as rapidly decaying, and therefore they'll have essentially the same trouble will harvesting them as other photovoltaics have. Furthermore, one won't be able to harvest all the energy from the visible spectrum even in principle: at a high level because of the second law of thermodynamics, and in the specific because the material will radiate as well.

2 points by nickb 18y ago

Damnit, journalism. How on earth did they get this: "Researchers at Ohio State University have accidentally discovered a new solar cell material capable of absorbing all of the sun's visible light energy. The material is comprised of a hybrid of plastics, molybdenum and titanium. The team discovered it not only fluoresces (as most solar cells do), but also phosphoresces. Electrons in a phosphorescent state remain at a place where they can be "siphoned off" as electricity over 7 million times longer than those generated in a fluorescent state. This combination of materials also utilizes the entire visible spectrum of light energy, translating into a theoretical potential of almost 100% efficiency. Commercial products are still years away, but this foundational work may well pave the way for a truly renewable form of clean, global energy." From this: "Oligothiophenes incorporating MM quadruple bonds have been prepared from the reactions between Mo2(TiPB)4 (TiPB = 2,4,6-triisopropyl benzoate) and 3′,4′-dihexyl-2,2′-:5′,2″-terthiophene-5,5″-dicarboxylic acid. The oligomers of empirical formula Mo2(TiPB)2(O2C(Th)-C4(n-hexyl)2S-(Th)CO2) are soluble in THF and form thin films with spin-coating (Th = thiophene). The reactions between Mo2(TiPB)4 and 2-thienylcarboxylic acid (Th-H), 2,2′-bithiophene-5-carboxylic acid (BTh-H), and (2,2′:5′,2″-terthiophene)-5-carboxylic acid (TTh-H) yield compounds of formula trans-Mo2(TiPB)2L2, where L = Th, BTh, and TTh (the corresponding thienylcarboxylate), and these compounds are considered as models for the aforementioned oligomers. In all cases, the thienyl groups are substituted or coupled at the 2,5 positions. Based on the x-ray analysis, the molecular structure of trans-Mo2(TiPB)2(BTh)2 reveals an extended Lπ-M2δ-Lπ conjugation. Calculations of the electronic structures on model compounds, in which the TiPB are substituted by formate ligands, reveal that the HOMO is mainly attributed to the M2δ orbital, which is stabilized by back-bonding to one of the thienylcarboxylate π * combinations, and the LUMO is an in-phase combination of the thienylcarboxylate π * orbitals. The compounds and the oligomers are intensely colored due to M2δ–thienyl carboxylate π * charge transfer transitions that fall in the visible region of the spectrum. For the molybdenum complexes and their oligomers, the photophysical properties have been studied by steady-state absorption spectroscopy and emission spectroscopy, together with time-resolved emission and transient absorption for the determination of relaxation dynamics. Remarkably, THF solutions the molybdenum complexes show room-temperature dual emission, fluorescence and phosphorescence, originating mainly from 1MLCT and 3MM(δδ* ) states, respectively. With increasing number of thienyl rings from 1 to 3, the observed lifetimes of the 1MLCT state increase from 4 to 12 ps, while the phosphorescence lifetimes are ≈80 μs. The oligomers show similar photophysical properties as the corresponding monomers in THF but have notably longer-lived triplet states, ≈200 μs in thin films. These results, when compared with metallated oligothiophenes of the later transition elements, reveal that M2δ–thienyl π conjugation leads to a very small energy gap between the1MLCT and 3MLCT states of <0.6 eV." http://www.pnas.org/content/105/40/15247.short http://www.pnas.org/content/105/40/15247.short The discovery of phosphorescent dual emission is a striking and important one, but there are dozens of hurdles still to create a solar cell, any one of which might be a nail in the coffin for the material. For example, just because some of the electrons end up in a triplet state doesn't mean all of them will: they've measured the singlet states as rapidly decaying, and therefore they'll have essentially the same trouble will harvesting them as other photovoltaics have. Furthermore, one won't be able to harvest all the energy from the visible spectrum even in principle: at a high level because of the second law of thermodynamics, and in the specific because the material will radiate as well.