Solar cells
We carry out search for third generation solar cells. Particularly, we seek and characterize such materials where thin-film or nanostructured semiconductors may show enhanced absorption and/or carrier multiplication for increased efficiency.
Contents
- 1 A new candidate for efficient solar cells: strongly correlated materials
- 2 Characterization of an efficient light absorber: point defects in tin monosulfide (SnS)
- 3 Enhanced absorption and carrier multiplication in semiconductor nanoparticles
- 3.1 Tweaking the absorption of Si nanoparticles by surface engineering
- 3.2 Solution to the quantum confinement dilemma: enhanced carrier multiplication rates in the solar spectrum in Si and Ge metastable nanoparticles
- 3.3 Efficient electron-hole separation for Si nanoparticles embedded into a matrix
- 4 Bibliography
Doi: 10.1103/PhysRevB.90.165142
Journal: Phys. Rev. B
Pages: 165142
Title: Optoelectronic excitations and photovoltaic effect in strongly correlated materials
Volume: 90
Year: 2014


We have shown by first-principles calculations that the carrier multiplication rate is two orders of magnitude higher in VO2 than in Si and much higher than the rate of hot electron/hole decay due to phonons. As VO2 is a proto-typical material of strongly correlated materials, we think that the family of strongly correlated materials exhibit similar properties. This may lead to a single photon in - two electrons out operation of solar cells in strongly correlated materials that can significantly increase the efficiency of this type solar cells compared to the case of conventional semiconductors. [1]Author: J. E. Coulter, E. Manousakis, A. Gali
Doi: 10.1103/PhysRevB.90.165142
Journal: Phys. Rev. B
Pages: 165142
Title: Optoelectronic excitations and photovoltaic effect in strongly correlated materials
Volume: 90
Year: 2014


Characterization of an efficient light absorber: point defects in tin monosulfide (SnS)
Tin monosulfide (SnS) is quasi-2D material which is a metastable crystalline form of Sn and S. From solar cell application point of view, the very attractive property of SnS is the strong absorption starting at about 1.3 eV. However, the real SnS material is very defective, and often exhibits unintentional p-type doping. In collaboration with Kaxiras group at Harvard University we found[2]Author: B. D. Malone, A. Gali, E. KaxirasDoi: 10.1039/C4CP03010A
Journal: Phys. Chem. Chem. Phys.
Pages: 26176-26183
Title: First principles study of point defects in SnS
Volume: 16
Year: 2014


Enhanced absorption and carrier multiplication in semiconductor nanoparticles
Surface effects on nanoparticle boundaries in solid-state matrix can help circumvent the limitations of traditional (first and second-generation) photovoltaics. This effect may be enhanced and fine-tuned by modifying the surface. The core aim of this strategy is to produce solid-state systems which absorb visible light, and in which the resulting high-energy exciton generates multiple charge carriers instead of decaying into a low-energy one by heating the solar cells.
Tweaking the absorption of Si nanoparticles by surface engineering
We calculated ab-initio the absorption of Si nanoparticles with various surface terminations [3]Author: M. Vörös, D. Rocca, G. Galli, G. T. Zimanyi, A. GaliDoi: 10.1103/PhysRevB.87.155402
Journal: Phys. Rev. B
Pages: 155402
Title: Increasing impact ionization rates in Si nanoparticles through surface engineering: A density functional study
Volume: 87
Year: 2013


Doi: 10.1021/nl901970u
Journal: Nano Letters
Note: PMID: 19785388
Number: 11
Pages: 3780-3785
Title: High-Energy Excitations in Silicon Nanoparticles
Volume: 9
Year: 2009


Doi: 10.1021/nl901970u
Journal: Nano Letters
Note: PMID: 19785388
Number: 11
Pages: 3780-3785
Title: High-Energy Excitations in Silicon Nanoparticles
Volume: 9
Year: 2009


Solution to the quantum confinement dilemma: enhanced carrier multiplication rates in the solar spectrum in Si and Ge metastable nanoparticles
Doi: 10.1039/C4TA01543F
Journal: J. Mater. Chem. A
Pages: 9820-9827
Title: Germanium nanoparticles with non-diamond core structures for solar energy conversion
Volume: 2
Year: 2014


Doi: 10.1103/PhysRevLett.110.046804
Journal: Phys. Rev. Lett.
Pages: 046804
Title: High-Pressure Core Structures of Si Nanoparticles for Solar Energy Conversion
Volume: 110
Year: 2013


Efficient electron-hole separation for Si nanoparticles embedded into a matrix
Solar cell application of the very promising silicon or germanium nanoparticles (NP) requires such a matrix where the photo-generated carriers can be efficiently separated and can be lifted to the contacts. The strong Coulomb interaction between the carriers in nanoparticles mediate the MEG process, however, this strong Coulomb interaction may also disadvantageously inhibit the efficient separation of the two types of carriers, electrons and holes, needed for photo-voltaics operation.
We propose that embedding silicon NP into amorphous, nonstoichiometric zinc-sulfide (ZnS) leads to promising nanocomposites for solar energy conversion. Using ab initio molecular dynamics simulations we show in collaboration with Giulia Galli group that, upon high temperature amorphization of the host chalcogenide, sulfur atoms are drawn to the NP surface. We find that the sulfur content may be engineered to form a type II heterojunction, with complementary charge transport channels for electrons and holes, and that sulfur capping is beneficial to lower the nanoparticle gap, with respect to that of NPs embedded in oxide matrices [7]Author: S. Wippermann, M. Vörös, A. Gali, F. Gygi, G. T. Zimanyi, G. GalliDoi: 10.1103/PhysRevLett.112.106801
Journal: Phys. Rev. Lett.
Pages: 106801
Title: Solar Nanocomposites with Complementary Charge Extraction Pathways for Electrons and Holes: Si Embedded in ZnS
Volume: 112
Year: 2014


Bibliography
[1] | J. E. Coulter, E. Manousakis, A. Gali: Phys. Rev. B, 90, 165142 (2014). Optoelectronic excitations and photovoltaic effect in strongly correlated materials | ![]() ![]() |
[2] | B. D. Malone, A. Gali, E. Kaxiras: Phys. Chem. Chem. Phys., 16, 26176-26183 (2014). First principles study of point defects in SnS | ![]() ![]() |
[3] | M. Vörös, D. Rocca, G. Galli, G. T. Zimanyi, A. Gali: Phys. Rev. B, 87, 155402 (2013). Increasing impact ionization rates in Si nanoparticles through surface engineering: A density functional study | ![]() ![]() |
[4] | A. Gali, M. Vörös, D. Rocca, G. T. Zimanyi, G. Galli: Nano Letters, 9, 3780-3785 (2009). High-Energy Excitations in Silicon Nanoparticles | ![]() ![]() |
[5] | M. Voros, S. Wippermann, B. Somogyi, A. Gali, D. Rocca, G. Galli, G. T. Zimanyi: J. Mater. Chem. A, 2, 9820-9827 (2014). Germanium nanoparticles with non-diamond core structures for solar energy conversion | ![]() ![]() |
[6] | S. Wippermann, M. Vörös, D. Rocca, A. Gali, G. Zimanyi, G. Galli: Phys. Rev. Lett., 110, 046804 (2013). High-Pressure Core Structures of Si Nanoparticles for Solar Energy Conversion | ![]() ![]() |
[7] | S. Wippermann, M. Vörös, A. Gali, F. Gygi, G. T. Zimanyi, G. Galli: Phys. Rev. Lett., 112, 106801 (2014). Solar Nanocomposites with Complementary Charge Extraction Pathways for Electrons and Holes: Si Embedded in ZnS | ![]() ![]() |