Optimal Design And Performance Of Photon Anode For High Efficiency Quantum Dot Sensitized Solar Cells

In recent years,in the context of excessive consumption of fossil fuels,the energy crisis and environmental pollution have become increasingly serious.The development of clean and renewable energy solar cells is one of the effective ways to solve the above problems.As a typical representative of the third-generation solar cells,quantum dot sensitized solar cells have been favored by researchers for their advantages such as good stability,low cost,simple preparation process,and high theoretical photoelectric conversion efficiency.Although the theoretical photoelectric conversion efficiency of quantum dots sensitized solar cells?QDSSCs?is high,the actual efficiency of the cells is still unstable and has not been greatly improved due to the constraints of materials and interface structures.Therefore,by optimizing the surface structure of the solar cell,increasing the light-capturing capacity of the quantum dots,widening the spectral absorption range of the quantum dots,increasing the absorbance of visible light,and the load of the quantum dots as the goals to improve the photoelectric conversion performance of the solar cell.This article focuses on the photoanodes of QDSSCs.The organic high temperature thermal injection method is used to synthesize high-quality quantum dots as sensitizers in advance.Optimizing the structure of the photoanode through ion doping and surface passivation can improve the conversion efficiency of the solar cell and improve the device performance.The specific work is as follows:?1?Effect of Ga³⁺doping in ZnS passivation layer for high efficiency Quantum dot-sensitized solar cellsThe application of quantum dots as photovoltaic materials in solar cells is becoming ever more widespread.Although the efficiency of solar cells has increased year by year,the commonly used quantum dot sensitizers still contain toxic and heavy metals such as Cd or Pb,which undoubtedly limits the use of such solar cells in the real life applications,the photoelectric conversion efficiency of"green"quantum dot solar cells that do not contain toxic and heavy metals is low,mainly due to the electronic recombination at the interface.Therefore,a wide-spectrum absorption range of Zn-Cu-In-Se?ZCISe?quantum dots?QDs?was synthesized by organic high-temperature thermal injection method in this paper,and the light absorption range can reach¹000 nm.The Ga³⁺-doped ZnS passivation layer was introduced on the surface of ZCISe QDs according to the continuous ion layer adsorption and reaction method?SILAR?to modify improve the solar cell performance.Metal ion doping is an effective method to change the inherent photoelectric properties of quantum dots.The power conversion efficiency?PCE?of quantum dot sensitized solar cells?QDSSCs?using ZCISe/Ga-ZnS quantum dots as sensitizers reached 8.72%(V_oc=0.594 V,J_sc=26.43 mA/cm²,FF=0.56).Studies have demonstrated that doping Ga in the ZnS layer can improve the light absorption of the solar cells.At the same time,the existence of Ga-ZnS passivation layer can also reduce the charge recombination at the interface.?2?Synthesis of Cu-In-Se?CISe?and Cu-In-Sn-Se?CISSe?quantum dots by organic high temperature hot injection methodTernary I-III-VI quantum dots?QDs?have attracted considerable attention in the field of photoelectric conversion applications.Quantum dots such as CuInSe and AgInS₂ not only have high absorption coefficient(¹0⁵ cm^-1),but also take the best optical band gap?¹.04eV?.Therefore,it is regarded as one of the ideal light absorbing materials and has broad application prospects.Here,we prepared Cu-In-Se?CISe?and Cu-In-Sn-Se?CISSe?QDs with relatively low toxicity by organic high-temperature hot-injection method and used them as quantum dot-sensitized solar cells?QDSSCs?Sensitizer.Since the suppression of charge recombination at the photoanode/electrolyte interface is one of the key factors to improve the efficiency of the solar cell,we have coated the CISS QDs surface with a ZnS high energy solar cell layer.ZnS is a semiconductor material with a wide band gap,higher and chemically stable,it can not only prevent the reverse transfer of electrons to the electrolyte,but also reduce the surface defect states of the quantum dots,thereby suppressing charge recombination and improving the collection efficiency of photo-generated electrons.In this paper,we use CISSe/ZnS QDSSCs as sensitizers to obtain 6.7%power conversion efficiency?PCE?,of which V_oc,J_scc and FF reached 0.559 V,22.93 mA/cm² and 0.52,respectively.