Recently the infrared quantum cutting has achieved an exciting development in enhancing the efficiency of solar cell. The infrared quantum cutting of Er0.3Gd0.7VO4 crystalline is studied in the present paper. It is found that the approximate quantum cutting efficiencies of 1532.5 nm 4I13/2→4I15/2 fluorescence, when the 2H11/2 and 4G11/2 levels are excited, are about 178.55% and 177.61% respectively. Especially, effective three-photon and four-photon infrared quantum cuttings of Er0.3Gd0.7VO4 crystalline excited by visible and near-violet light are found for the first time in the present paper. An interesting "peak - valley" conversion phenomenon in the excitation spectrum is also observed. It is also the first time for us to find the first-order infrared quantum cutting based single species Er3+ ion for Er0.3Gd0.7VO4 crystalline.
Infrared quantum cutting of rare earth ion is an international hot research field. It is significant for the enhancement of solar cell efficiency and for the reduction of solar cell price. The present paper summarizes the research significance of infrared quantum cutting of rare earth ion. Based on the summarization of general principle and loss mechanism of solar cell, the possible method to enhance the solar cell efficiency by infrared quantum cutting is analyzed. Meanwhile, the present paper summarizes the infrared quantum cutting phenomena of Er3+ ion single-doped material. There is intense 4I13/2 --> 4I15/2 infrared quantum cutting luminescence of Er3+ ion when the 2H11/2 energy level is excited. The intense {2H11/2 --> 4I9/2, 4I15/2 --> 4I13/2} cross energy transfer is the main reason for the result in the high quantum cutting efficiency when the 2H11/2 energy level is excited.
The infrared quantum cutting phenomena, which is an international hot research field, of Er1.0P5O14 noncrystalline glass are studied by the present paper for the first time. The 1537.0nm infrared fluorescence of Er1.0P5O14 noncrystalline glass is confirmed to be the multi-photon quantum cutting fluorescence by computation and comparison between absorption and excitation spectra. It is found that the 4I13/2→4I15/2 quantum cutting fluorescence is very strong, induced by the excited 2H11/2, 4G11/2, and 4G9/2 energy levels. Its mechanism is thoroughly analyzed based on the calculation of spontaneous emission rates, nonradiative multiphonon relaxation rates and energy transfer rates. It is found the strong downconversion energy transfers {2H11/2→4I9/2,4I15/2→4I13/2},{4G11/2→4I13/2, 4I15/2→2H11/2},{4G9/2→4F7/2,4I15/2→4I13/2} 和 {4G9/2→4I13/2, 4I15/2→2H11/2} are responsible for the strong infrared three-photon and four-photon quantum cutting fluorescence of Er1.0P5O14 noncrystalline glass. The present research is significant for enhancing solar cell efficiency.
The efficiency of single-junction solar cells is limited to about 30% (the Shockley-Queisser limit). Spectral mismatch losses (transparency to low-energy photons, thermalization of high-energy photons) strongly contribute to lowering the maximum efficiency. To reduce thermalization losses, photon splitting is proposed and observed for a variety of lanthanide-doped materials. For
Er3+, even a one-to-three photon-splitting process has been reported, yielding three IR photons at around 1530 nm following absorption of one blue-green photon. This is especially beneficial for narrow band gap solar cells, such as crystalline
Ge. Here, we report on photon splitting for
Er3+ in
YVO4. Following absorption in the
2H11/2 and
4S3/2 levels (520--550 nm), efficient cross-relaxation (CR) yields two excited
Er3+ ions: one in the
4I9/2 state and one in the
4I13/2 state (CR1). A second CR step from the
4I9/2 state, leaving both
Er3+ ions in the
4I13/2 excited state (CR2), is crucial in realizing efficient three IR photon splitting. It is demonstrated here that the second step has a low efficiency, as a result of competing fast multiphonon relaxation, ${}^{4}{\mathrm{I}}_{9/2}{\ensuremath{\rightarrow}}^{4}{\mathrm{I}}_{11/2}$, and a large energy mismatch, which makes the CR2 step thermally activated. Based on experiments and theory, a maximum quantum efficiency of 170% is calculated for IR emission, following blue-green excitation in
YVO4:Er3+. An outlook is presented for three-photon splitting in low-phonon-energy hosts, where nonradiative multiphonon relaxation is suppressed. The anti-Stokes nature of the second CR step makes three-photon splitting unlikely and prevents the realization of IR quantum yields above 200%.
The infrared quantum cutting phenomena of Er0.1Gd0.9VO4 crystal are studied in the present article. An interesting host sensitized infrared quantum cutting phenomenon is found, that is, there is a strong and broad excitation peak at 337.0 nm wavelength for its excitation spectrum of 1537.5 nm 4I13/24I15/2 infrared fluorescence. It can be recognized that the 337.0 nm excitation peak corresponds to the absorption of host GdVO4 crystal. Meanwhile, it is found that the integral fluorescence intensity of 1537.5 nm 4I13/24I15/2 infrared fluorescence, when the host absorption band is excited by 337.0 nm light, is about ten times larger than that of the sum of all other fluorescence intensities. Its infrared quantum cutting efficiency is similar to that of the excited 2H11/2 energy level and larger than that of others.
Abstract Quantum cutting (QC) is a process that can split one high-energy photon into two or more low-energy photons.1-4 As an attractive mechanism, it has been extensively explored for acquiring high quantum efficiency (QE) of more than 100%.5-8 Here, we report the first experimental observation of multiphoton QC with ultrahigh QEs in CaF2:Yb polycrystalline. Under 266 nm excitation, an internal quantum efficiency as high as ~285% was achieved, indicating that one ultraviolet (UV) photon was split into more than two ~1000 nm near infrared (NIR) photons. Photovoltaic experiments demonstrated that the polycrystalline increased the output power of a polycrystalline silicon solar cell by more than 200% in the case of 266 nm irradiation. Spectral analysis confirmed that the ultrahigh QE originated from efficient cooperative absorptions of Yb-tetramers and Yb-trimers and individual emission of single Yb3+ ions. This study provides a promising approach for improving spectral response of silicon solar cells and detectors in the UV region.