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As the improvement in efficiency of CdTe solar cell becomes more and more difficult, it is very necessary to engage in research on CdTe solar cell with innovative structure or new materials. In this work, we first proposed a design idea of constructing cadmium telluride on silicon to form a CdTe/Si composite absorption layer and then achieving an innovative high efficiency solar cell with a basic structure of n-Zn 1-x Mg x O/p-CdTe/p-Si/Au. This kind of solar cell has the advantages of relatively high open-circuit voltage and large short-circuit current, because photons with a wavelength range of 825 nm–1100 nm can not be absorbed by CdTe with a bandgap of 1.5 eV while they can be absorbed by silicon with a bandgap of 1.12 eV, thereby extending the long-wave response of sunlight. Numerical simulation of solar cell was carried out by using SCAPS-1D software to study the impacts of materials parameters such as thickness, doping concentration, valence band offset (VBO) and interface state density of CdTe/Si on device performances. Results indicated that thinner CdTe and suitable thick Si were beneficial for the cell with high efficiency. Particularly, the interface states between CdTe and Si severely degraded cell performance, so an innovative CdSi x Te y layer was proposed for the first time to effectively reduce the lattice mismatch and modify the interface properties between CdTe and Si. Finally, the highest theoretical conversion efficiency of 28.36% accompanied by open-circuit voltage of 0.838 V, short-circuit current of 39.28 mA/cm2, and fill factor of 86.11% of solar cell with SnO 2 :F/Zn 1-x Mg x O/CdTe/CdSi x Te y /Si/ZnTe:Mo/Au structure was obtained by optimizing numerical simulation design. An innovative solar cell structure with a CdTe/Si composite absorber (not tandem cell) is proposed. Numerical simulation show that cell of this structure can achieve high theoretical efficiency by effectively extending the long-wave response to about 1100 nm compared with conventional CdTe solar cell Image 1 • An innovative high efficiency solar cell with CdTe/Si composite absorber (not tandem cell) was proposed. • Numerical simulation results indicated that the EQE of CdTe/Si composite absorber solar cell was extended to about 1100 nm. • Highest theoretical conversion efficiency of 28.36% of this solar cell was obtained by optimized numerical simulation design. [ABSTRACT FROM AUTHOR]