ABSTRACT
All non-stoichiometric silicon carbide (Si x C1−x )-based solar cell (SC) have been demonstrated by using the plasma PECVD system. The C/Si composition ratio of the non-stoichiometric Si x C1−x film grown at the RF plasma power density of 110 mW/cm2 is obtained as 0.503. The non-stoichiometric SixC1−x has a high-optical absorption coefficient of 2.1 × 105 cm−1 at the visible region, which corresponds to the optical band gap energy of 2.04 eV. When using the non-stoichiometric Si x C1−x with the C/Si composition ratio of 0.503 as the n-type and p-type layer,− the non-stoichiometric Si x C1−x -based p–n junction SC with the n-type Si x C1−x thickness of 50 nm obtains its conversion efficiency of 0.37%. To enhance the conversion efficiency, the non-stoichiometric Si x C1−x -based p–i–n junction SC by adding the intrinsic Si x C1−x layer is demonstrated. Moreover, the series resistance of the non stoichiometric Si x C1−x film is optimized by adjusting the resistivities of the n-type and p-type Si x C1−x film in order to enhance its conversion efficiency. By doping with the PH3 and B2H6 fluence ratios of 4.2 and 2.1%, the resistivities of n-type and p-type non-stoichiometric Si x C1−x films are improved to 0.87 and 0.12 Ωcm, respectively. On the other hand,− the intrinsic non-stoichiometric Si x C1−x thickness can further obtain the higher conversion efficiency of devices. The non-stoichiometric Si x C1−x -based p–i–n junction SC with the intrinsic non-stoichiometric Si x C1−x /a-Si-based tandem SC, its open-circuit voltage (V oc) 62and short-circuit PC density (J sc) are acquired as 0.78 V and 19.1 mA/cm2, respectively, which leads to the conversion efficiency and FF of 5.24% and 0.29. Finally, the intrinsic Si x C1−x film changes its C/Si composition by detuning the [CH4]/[CH4+SiH4] fluence ratio (R SiC) to further enhance the conversion efficiency of the non-stoichiometric Si x C1−x -based SCs. By fixing the R SiC at 0.3, the C/Si composition ratio of non-stoichiometric Si x C1−x films reduces to 0.36. The absorbance of non-stoichiometric SixC films 1 x grown with an R SiC of 0.3 is enhanced to 3.8 × 105 cm−1. Because of the increasing absorbance of the intrinsic Si x C1−x film, the V oc and the J sc of the non-stoichiometric Si x C1−x -based p–i–n junction SC are enhanced to 0.51 V and 19.7 mA/cm2, respectively, which promote the conversion efficiency up to 2.24% with an FF of 0.283. For the non-stoichiometric Si x C1−x /a-Si tandem SC with the intrinsic SixC1− x layer grown with x the R SiC of 0.3, it exhibits a highest conversion efficiency of 6.47% and an optimized FF of 0.332.
