The IBC structure is one of the champions in the efficiency competition of silicon devices. Industrial cells are produced with efficiency values surpassing 24%, what is due to an excellent design in terms of separation from the region where carriers are energized and emitters where these carriers are selectively separated. Their position in the back of the cell allows the access to both quasi-Fermi-levels from this surface, and enables the access to their corresponding levels of top or bottom cells from this place, far away from the entrance of light and simplifying the design of complex multi-band-gap structures. This paper will shown several of these structures, many of them achievable with well known materials with technology developed for the microelectronic sector. These solutions would be to cells with efficiencies in the 30-32 %. Using optimum materials, not clear at this moment, we estimate a technological limit of 39.4 % for these new structures.