NOVELTY - Texturing a crystalline-silicon (c-Si) substrate involves pretreating the c-Si substrate with a hydrogen fluoride solution; and texturing the c-Si substrate with a texturing solution comprising potassium hydroxide and butanol.    USE - For texturing a crystalline-silicon (c-Si) substrate (claimed) for use in silicon based solar cell.    ADVANTAGE - The texturing solution produces a texture having good light trapping characteristics. The texturing solution has highest roughness value, which indicates higher randomness in the pyramid size and randomness in the pyramid distribution, both of which provide the best light trapping. The texturing solution can be optimized to tune the textured surface to have a predetermined texture profile that can provide maximized light trapping for a solar cell. The crystalline silicon based solar cells are much more efficient when the silicon substrate is capable of trapping light because greater conversion of that light to energy can occur. The HF (hydrogen fluoride) pretreatment in combination with the texturing of the crystalline silicon substrate improves solar cell to cell texture uniformity.    DETAILED DESCRIPTION - INDEPENDENT CLAIMS are included for the following:    (1) a crystalline silicon texturing formulation comprising potassium hydroxide (KOH) (less than approximately 1.5 M), butanol (2-8 volume percent), and water, where the formulation has a temperature of 60-100 degrees C; and    (2) a combinatorial method of tuning a silicon texturing solution to texture a crystalline silicon substrate to have predetermined characteristics involving screening several silicon texturing solutions having varied concentrations to identify a first subset of silicon texturing solutions that provide a texture on a c-Si substrate, where the texture comprises pyramids having a height and a distribution within a predetermined range; screening the first subset of silicon texturing solutions having varied temperatures and substrate application times to identify second subset of silicon texturing solutions capable of etching the c-Si substrate within a predetermined time; and screening the second subset of silicon texturing solutions having varied formulations by applying the second subset to substrates that are larger than substrates used for screening the silicon texturing solutions and the first subset of silicon texturing solutions, where the second subset is selected based on an ability of the texturing solution to provide a texture on the c-Si substrate having optical reflection measurements within a predetermined range.