Abstract: With their nano-engineered feature, Photonic Crystals (PhCs) allow the best control of the propagation and absorption of light in an increased way. In our work, we applied the Rigorous Coupled Wave Analysis (RCWA) method to calculate the diffraction efficiency, field distribution, for a specific incidence angle and absorption energy in a periodic structures using unpatterned, 1DPhC, half circle and triangular grating structures with both a-Si:H, a-SiGe:H thin film semiconductor materials with different gratings of PhCs to improve optical absorption, taking into account the J-V solar cell characteristics. According to our simulation, the ideal result was in the case of triangular grating with a-SiGe:H semiconductor material so for the presence of Germanium, which enhances light absorption by reducing the band gap energy. The optical light absorption was more than 85.7% by increase the lattice parameter from 0.3µm to 0.5µm. Moreover, we found a solar cell efficiency enhancement of 16.6%, with a total improvement of 7.74%; as compared with unpatterned grating. Concerning the incidence angle effect, the better one is ranged between 50° and 70° with a peak absorption ratio of 99%. Keywords: Photonic crystals, RCWA, Incidence angle, Triangular grating, Solar cell.