The growth of DAST (4-N,N-dimethylamino- 4,-N,-methylstilbazolium tosylate) crystal with large (001) surface area is challengingbut necessary for intense broadband Terahertz(THz) sources. Here, the effect of the growth solution concentration on the crystal shapewere studied by slope nucleation method-coupled slow cooling(SNM-SC) technique. With careful control over the growth conditions, DASTcrystals with large (001) surface area were harvested. Surface morphology shows good surface quality. Without further surface polishing,this allowed to generate single cycle THz pulses with high optical-to-THz conversion efficiency reaching 0.66%.