Silicon heterojunction (SHJ) solar cells are expected to expand their share in the photovoltaic industry in coming years due to high power conversion efficiency, lean fabrication process and low temperature coefficient [1,2]. This work presents several key points and gives an inclusive analysis during the development of our M2-size SHJ solar cells with a certified champion efficiency of 24.51%. We aim at giving the readers a comprehensive understanding of the design principles towards high efficiency SHJ solar cells. In this study, we mainly investigated five aspects in the fabrication of SHJ solar cells. i) The comparison between using different n-type window layers including hydrogenated amorphous silicon (a-Si:H), hydrogenated nanocrystalline silicon (nc-Si:H) and hydrogenated nanocrystalline silicon oxide (nc-SiOx:H). ii) The microstructure of p-side intrinsic a-Si:H bilayers and its influence on solar cells performance. iii) The impact of p-side Sn-doped In2O3 (ITO) bilayers on solar cells performance. iv)The development of thin finger printing. v) The optimization of full area Ag back reflector.