Research On Spectral Dowen-Conversion Of The Rear-Earth Doped Material And Its Application

Solar cells are photovoltaic devices which convert light energy intoelectrical energy through photovoltaic effect. In the photoelectric conversionprocess of solar cells, the mismatch between solar energy and band gapenergy of cells material cause part of energy loss, which will limit theconversion efficiency of solar cells. Spectral conversion is an effectivemethod to reduce such energy loss. A high-energy photon could be convertedinto two or more low-energy photons by spectral down-conversion and it canimprove the utilization of high-energy photons in solar cells. Rare-earthdoped material is commonly used for down-conversion because of itsfluorescence properties. Researches on down-conversion of rare-earth dopedmaterial is significant for improving the conversion efficiency of solar cells.In this paper, we study the spectral down-conversion effect of therare-earth ions co-doped material and its photovoltaic application, anddiscuss the impact of spectral down-conversion on the output performanceof solar cells. Therefore, the work of this paper generally can be divided intotwo parts:the first part is the modeling and the simulation on process ofspectral down-conversion of rare-earth ions co-doped system; the secondpart is simulation on solar cells performance, thus this part is the specific application of the first part.The main work in this paper includes:1. We study the spectral down-conversion function of the Ce³⁺-Yb³⁺ions co-doped glass system. By analysing the process of energy transferfrom Ce³⁺ ions to Yb³⁺ ions, we establish a theoretical model for this process.At the same time in order to analyse down-conversion efficiencyquantitatively, the power conversion efficiency, photon conversion efficiencyand quantum efficiency are defined.2. Simulation of the above mentioned numerical model is executed byusing MATLAB. The theoretical model is solved by simulation after we setthe initial value for certain parameters and select the appropriate method ofcalculation. By analyzing the simulation results, we get the followingconclusion: Ce³⁺-Yb³⁺ ions co-doped glass system can effectively converthigh-energy photons into low-energy ones fitting for absorption andutilization of solar cells.3.Using the solar spectrum and the spectrum after down-conversion asexcitation spectrum, we carry out simulation of solar cells. This section alsocan be divided into two aspects: one is the simulation through PC1Dsoftware, and the other is the simulation by programming to solve equationswith MATLAB ,based on the existing basic physical formula. Comparing thesimulation results, we find that the short circuit current, the open circuit voltage and the conversion efficiency of solar cells have been improved tosome extent under the excitation of down-conversion spectrum.