Efficiency improved by acid texturization for multi-crystalline silicon solar cells

In this paper, we will show that efficiency of multi-crystalline silicon (mc-Si) solar cells may be improved by acid texturization. In order to enhance overall efficiency of mc-Si for solar-cell applications, the surface treatment of texturization with wet etching using appropriate solutions can improve incident light into the cell. Alkali etchant cannot produce uniformly textured surface to generate enough open circuit voltage (VOC) and high efficiency of the mc-Si due to the unavoidable grain randomly oriented with higher steps formed during etching process. Optimized acid etching conditions can be obtained by decreasing the reflectance (R) for mc-Si substrate below levels generated by alkali etching. Short-circuit current (ISC) measurements on acid textured cells reveal that current gain can be significantly enhanced by reducing reflection. The optimal acid etching ratio HF:HNO3:H2O = 15:1:2.5 with etching time of 60 s and lowering 42.7% of the R value can improve 112.4% of the conversion efficiency (η) of the developed solar cell. In order to obtain more detailed information of different defect region, high-resolution light beam induced current (LBIC) is applied to measure the internal quantum efficiency (IQE) and the lifetime of minority carriers. Thus, the acid texturing approach is instrumental to achieve high efficiency in mass production using relatively low-cost mc-Si as starting material with proper optimization of the fabrication steps.