NOVELTY - A silicon-based thin film solar cell with gradient structure has positive-negative (pn) junction. The gradient structure has transition of energy gap of amorphous silicon carbide of 2.1-2.3eV to energy gap of nano-crystalline silicon carbide of 1.8-2.1eV, where the energy gap of gradient structure is uniformly reduced in form of energy gap of 0.01-0.1eV.    USE - Silicon-based thin film solar cell with gradient structure (claimed).    ADVANTAGE - The solar cell absorbs more sunlight and converts into electric energy, thus generating larger current, and is free of holes and cracks, and more compact and uniform.    DETAILED DESCRIPTION - A silicon-based thin film solar cell with gradient structure has positive-negative (pn) junction. The gradient structure has transition of energy gap of amorphous silicon carbide of 2.1-2.3eV to energy gap of nano-crystalline silicon carbide of 1.8-2.1eV, where the energy gap of gradient structure is uniformly reduced in form of energy gap of 0.01-0.1eV. The gradient structure has transition of energy gap of amorphous silicon of 1.7eV to energy gap of nano-crystalline silicon of 1.7eV-1.2eV, where the energy gap of gradient structure is uniformly reduced in form of energy gap of 0.01-0.1eV. The gradient structure has transition of energy gap of amorphous silicon-germanium (Si(1-x)Ge(x)) of 1.7eV to 1.2eV to energy gap of amorphous silicon-germanium of 1.5eV to 1.2eV, where the energy gap of gradient structure decreases with decrease of ratio of silicon and germanium in form of energy gap of 0.01-0.1eV, and x is 0-1. The gradient structure has transition of energy gap of nano-crystalline silicon of 1.7eV to 1.2eV to energy gap of nano-crystalline silicon of 1.5eV to 1.1eV, where the energy gap of gradient structure is uniformly reduced in form of energy gap of 0.01-0.1ev. The gradient structure has transition of energy gap of nano-crystalline silicon of 1.5eV to 1.2eV to energy gap of microcrystalline silicon of 1.1eV, where the energy gap of gradient structure is reduced in form of energy gap of 0.01-0.1eV. An INDEPENDENT CLAIM is included for preparation of silicon based thin film solar cell with gradient structure.