Applied Research Of The Bidirectional?up And Down?-conversion Luminescence Agent(GdBO₃:Yb³⁺/Tb³⁺)in CdSe_0.4S_0.6 Quantum Dot-sensitized Solar Cells

With the continuous evolution of human society,the development of clean renewable energy sources and their improvement of conversion efficiency have become international hotspots and problems.Therefore,photoelectric conversion cells have received a lot of attention,due to they can directly convert the solar energy that the most abundant clean energy on the planet into electrical energy.Among them,quantum dot sensitized solar cells?QDSSCs?attract many researchers because of their low cost and high theoretical energy conversion efficiency.From the current research,multicomponent inorganic semiconductor quantum dots sensitizers are valued for their outstanding light stability,band gap tunability,high molar extinction coefficient and multiple exciton generation effects,for example,CdSe_xS_1-x.Nevertheless,for the continuous and wide solar spectrum,CdSe_xS_1-x can only absorb the visible light,while the most of ultraviolet and near-infrared lights cannot be utilized to form photocurrent,which results in low-level solar light utilization rate.Therefore,broadening the light absorption range and enhancing the solar light utilization rate of the QDSSCs are two urgent tasks at present.In recent years,the utilization of luminescent materials to adjust the incident light spectrum,increase the photoresponse range of solar cells and increase their photoelectric conversion efficiency have become one of the hot topics in the current academic and industrial research.Among kinds of the studied luminescence materials,the GdBO₃:Yb³⁺/Tb³⁺nanoparticles with the unique characteristics of bidirectional?up and down?-conversion luminescence have been attracted significant interest in the potential application.Taking into account the excellent optical properties and the stability,the GdBO₃:Yb³⁺/Tb³⁺should display immense potential in solar cells.When the GdBO₃:Yb³⁺/Tb³⁺nanoparticles are excited by 383 nm and 980 nm wavelengths of lights,it can emit the visible light ranging from 450 nm to 650 nm.Besides,the visible light can be reflected by GdBO₃:Yb³⁺/Tb³⁺nanoparticle,because it hardly absorbs visible light.Therefore,the GdBO₃:Yb³⁺/Tb³⁺nanoparticle can be combined with the middling band-gap?1.9 eV-2.7 eV?QDs and indirectly broaden the light absorption range of QDs.Meanwhile,in order to perfectly match the light absorption range of CdSe_xS_1-x with the emission spectrum of GdBO₃:Yb³⁺/Tb³⁺,the proportion of Se and S elements in CdSe_xS_1-x QDs is adjusted to form CdSe_0.4S_0.6.Thus,the purposes of expanding the light absorption range of QDs to ultraviolet and infrared ranges and enhancing the light capture capability of QDSSCs can be achieved.Based on the above considerations,a novel,simple and low-cost CdSe_0.4S_0.6/(GdBO₃:Yb³⁺/Tb³⁺@TiO₂)photoanode is designed and employed in CdSe_0.4S_0.6 QDSSCs.In this study,the CdSe_0.4S_0.6/(GdBO₃:Yb³⁺/Tb³⁺@TiO₂)photoanode is fabricated by simple sol-gel drop-coating method and successive ionic layer adsorption and reaction?SILAR?technique at room temperature.The UV-vis absorption spectroscopy and photoluminescence property of the photoanode films are systematically studied.In addition,the photoelectric performance of the CdSe_0.4S_0.6QDSSCs device is also studied by current density-voltage measurement.Through the comprehensive analysis of the prepared photoanode films,the results show that the addition of bidirectional?up and down?-conversion luminescence agent(GdBO₃:Yb³⁺/Tb³⁺)into TiO₂ photoanode can effectively enhance the short-circuit current(J_sc)and the open-circuit voltage(V_oc)of the CdSe_0.4S_0.6 QDSSCs.The research results demonstrate a potential of bidirectional?up and down?-conversion luminescence agent in QDSSCs.It provides a possible strategy for future research on solar cells to achieve a substantial enhance in energy conversion efficiency.