| AVS 65th International Symposium & Exhibition | |
| Thin Films Division | Tuesday Sessions |
| Session TF+AS-TuM |
| Session: | Special Session in Honor of Paul Holloway: Luminescent Materials Growth, Synthesis and Characterization |
| Presenter: | Hendrik C Swart, University of the Free State, Republic of South Africa |
| Authors: | H.C. Swart, University of the Free State, Republic of South Africa J.J. Terblans, University of the Free State, Republic of South Africa R.E. Kroon, University of the Free State, Republic of South Africa E. Coetsee, University of the Free State, Republic of South Africa M.M. Duvenhage, University of the Free State, Republic of South Africa E. Hasabeldaim, University of the Free State, Republic of South Africa A. Balakrishna, University of the Free State, Republic of South Africa A. Kumar, University of the Free State, Republic of South Africa P.H. Holloway, University of Florida |
| Correspondent: | Click to Email |
Luminescent compounds and materials have numerous uses. The emission properties, whether of a fast decay rate fluorescent material or a slow decay rate phosphorescent material, are defined by the chemical composition and the physical structure of the luminescent material. The crystal field that is determined by the environment in the host material in combination with the various dopant ions with the correct valence state can be used to obtain emissions from the Ultra violet (UV) to the infra-red (IR) wavelength ranges. Phosphor materials have been successfully used to improve the efficiency of various applications. Nanoparticles both undoped and doped with different rare earth elements were synthesized by several synthesized techniques. The major problem that limits solar cells’ efficiency is their insensitivity to the whole solar spectrum which is the so-called spectral mismatch. Therefore, several mechanisms have been explored based on photoluminescence (PL) to convert the solar cell spectrum where the spectral response of the solar cell is low to regions where the spectral response of the solar cell is high. For single crystalline silicon (Si) photovoltaic (PV) cells with a rather small semiconductor band-gap (Eg: 1.12 eV, corresponding to a wavelength of ~1100 nm), the transmission loss of the sub-band-gap photons can still amount to about 20% of the sun’s energy irradiated onto the Earth’s surface. For PV cells with a larger band-gap, such as amorphous Si (Eg: 1.75 eV) solar cells, which are limited to absorb sunlight with wavelengths below 708 nm, manifest even higher near infrared transmission losses. Downconversion, up-conversion (UC) and downshifting are some of the mechanisms that may be applied to improve the spectral response. Upconversion nanoparticles (UCNPs) have shown some promising possibilities to be considered in this respect, however, low UC efficiency of UCNPs is still the most severe limitation of their applications. In downshifting the strong deep level emission (DLE) and near band edge emission could be tuned to cover a wide spectral range. The strong DLE, covering a wide spectral range of ~375-650 nm, signifies the potential optoelectronics application in the near white LED applications. Degradation of the different phosphors during prolonged electron/photon bombardment also played a vital role in their possible applications. Examples of different phosphor materials with different applications such as Solid State Lighting will be shown.