Improving solar cell efficiencies by up-conversion of sub-band-gap light

Trupke, Thorsten; Green, Martin A.; Würfel, P.

doi:10.1063/1.1505677

Cited by 770 publications

(558 citation statements)

References 9 publications

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“…There are many examples of efficient UC and DC using lanthanides, either with one type of lanthanide ion or a pair of lanthanide ions. 3,4 Trupke et al [5][6][7] have performed extensive calculations to determine the effect of using either UC or DC materials in combination with solar cells. With an ideal downconverter material ͑splitting every photon above 2 E g into two photons that both can be absorbed͒ a limit of efficiency of 40% is possible for a solar cell with a band gap of 1.1 eV.…”

Section: Introductionmentioning

confidence: 99%

Downconversion for solar cells in NaYF4:Er,Yb

Aarts

Ende

Meijerink

2009

Journal of Applied Physics

197

117

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Downconversion is a promising avenue to boost the efficiency of solar cells by absorbing one higher energy visible photon and emitting two lower energy near-infrared ͑NIR͒ photons. Here the efficiency of downconversion for the ͑Er 3+ ,Yb 3+ ͒ couple is investigated in NaYF 4 , a well-known host lattice for efficient upconversion with ͑Er 3+ ,Yb 3+ ͒. Analysis of the excitation and emission spectra for NaYF 4 doped with 1% Er 3+ and codoped with 0%, 5%, 10%, or 30% Yb 3+ show that visible to NIR downconversion is inefficient. Downconversion by the scheme based on the reverse of the upconversion process is hampered by fast multiphonon relaxation from the 4 F 7/2 level ͑the starting level for downconversion͒ to the 4 S 3/2 level. Energy transfer from the 4 S 3/2 level of Er 3+ to Yb 3+ is shown to be inefficient. Efficient downconversion from the 4 G 11/2 of Er 3+ level is observed, resulting in emission of two photons ͑one around 980 nm and one around 650 nm͒ after absorption of a single 380 nm photon.

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Section: Introductionmentioning

confidence: 99%

Downconversion for solar cells in NaYF4:Er,Yb

Aarts

Ende

Meijerink

2009

Journal of Applied Physics

197

117

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“…For all-optical switching and sensor protection applications 8 as well as in the absorption of the subband-gap light for the possible solar cell applications, 9 the nonlinear refractive index coefficient, also known as the optical Kerr index, n 2 , and two-photon absorption coefficient, ␤, are the two crucial third-order optical nonlinearities that play an important role. Recent experiments show that Ge NCs have enhanced third-order optical nonlinearities.…”

Section: Introductionmentioning

confidence: 99%

Bound-state third-order optical nonlinearities of germanium nanocrystals embedded in a silica host matrix

Yıldırım

Bulutay

2008

Phys. Rev. B

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Embedded germanium nanocrystals ͑NCs͒ in a silica host matrix are theoretically analyzed to identify their third-order bound-state nonlinearities. A rigorous atomistic pseudopotential approach is used for determining the electronic structure and the nonlinear optical susceptibilities. This study characterizing the two-photon absorption, nonlinear refractive index, and optical switching parameters reveals the full wavelength dependence from static up to the ultraviolet spectrum, and the size dependence up to a diameter of 3.5 nm. Similar to Si NCs, the intensity-dependent refractive index increases with decreasing NC diameter. On the other hand, Ge NCs possess about an order of magnitude smaller nonlinear susceptibility compared to Si NCs of the same size. It is observed that the two-photon absorption threshold extends beyond the half band-gap value. This enables nonlinear refractive index tunability over a much wider wavelength range free from two-photon absorption.

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“…The reverse of this type of process could produce bandgap photons of short-wavelength, high-energy photons (down conversion). These schemes have been explored theoretically and predicted to produce device efficiencies of 63% for up conversion and 40% for down conversion (Trupke et al, 2002). NLO crystals are routinely used to efficiently perform these types of conversion.…”

Section: Spectral Conversionmentioning

confidence: 99%

Photovoltaic technologies

2008

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a b s t r a c tPhotovoltaics is already a billion dollar industry. It is experiencing rapid growth as concerns over fuel supplies and carbon emissions mean that governments and individuals are increasingly prepared to ignore its current high costs. It will become truly mainstream when its costs are comparable to other energy sources. At the moment, it is around four times too expensive for competitive commercial production. Three generations of photovoltaics have been envisaged that will take solar power into the mainstream. Currently, photovoltaic production is 90% first-generation and is based on silicon wafers. These devices are reliable and durable, but half of the cost is the silicon wafer and efficiencies are limited to around 20%. A second generation of solar cells would use cheap semiconductor thin films deposited on low-cost substrates to produce devices of slightly lower efficiency. A number of thin-film device technologies account for around 5-6% of the current market. As second-generation technology reduces the cost of active material, the substrate will eventually be the cost limit and higher efficiency will be needed to maintain the cost-reduction trend. Third-generation devices will use new technologies to produce high-efficiency devices. Advances in nanotechnology, photonics, optical metamaterials, plasmonics and semiconducting polymer sciences offer the prospect of cost-competitive photovoltaics. It is reasonable to expect that cost reductions, a move to second-generation technologies and the implementation of new technologies and third-generation concepts can lead to fully costcompetitive solar energy in 10-15 years.

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Improving solar cell efficiencies by up-conversion of sub-band-gap light

Cited by 770 publications

References 9 publications

Downconversion for solar cells in NaYF4:Er,Yb

Downconversion for solar cells in NaYF4:Er,Yb

Bound-state third-order optical nonlinearities of germanium nanocrystals embedded in a silica host matrix

Photovoltaic technologies

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