TECHNOLOGY FOCUS - INORGANIC CHEMISTRY - Preferred Solar Cell: In the solar cell, the substrate is the polysilicon thin board. The poly-silicon thin plate is 120 to 126 mm thick and the resistance change range is 5% to 30%. The optical converter is 20 to 200 mm thick. The refraction coefficient of the optical converter is n = 1.35 to 1.70. In the optical converter (A), the weight ratio between the inorganic phosphor and the organic polymer material is 0.05% to 10%. In the optical converter (B), the percentage of the carbon nano-tube by weight is 0.01% to 0.5%. In the optical converter (C), the weight ratio between the inorganic phosphor and the organic polymer material is 0.05% to 10%. In the optical converter (C), the weight ratio between the carbon nano-tube and the inorganic phosphor is 1% to 10%. The organic polymer material is selected from the epoxy resin, the organic silicon material or the mixture of both. The organic polymer material is the mixture of the epoxy resin and the polyamide with the weight ratio to be 1:1. The inorganic phosphor is made of rare earth element oxides with the chemical formula to be (LnO)nA; Ln refers to the Y (+3), the La (+3), the Gd (+3) or the Lu (+3) or the combination, and when n = 1, A is the halogen F-, Cl-, Br- or I-, and when n = 2, A is the chalcogen S (-2) or the Se (-2); the component of the activator for the inorganic phosphor is the Yb (+3), the Er (+3), the Ho (+3) or the Tm (+3) or the combination. The activator takes up 0.1% to 40% of the inorganic phosphor by weight. The absorption range of the inorganic phosphor to the near infrared radiation is 800 to 1200 nm. The geometric dimension of the inorganic phosphor is smaller than the maximum radiating wavelength of the sunlight. The geometric dimension of the inorganic phosphor is 60 to 80 nm. The carbon nano-tube is prepared with the vapor synthesis method with the raw material to be the methane CH4 or the ethane C2H6, and in the vapor synthesis method, the Ni, Co or Fe thin plate selected from the group VIII elements to serve as the catalyst. The carbon nano-tube is 10 to 20 nm in diameter and 100 to 400 nm in geometric length. The solar cell is the poly-silicon solar cell.