A variety of novel fullerene materials, showing different electron accepting capabilities, has been synthesized and used to prepare electron transport layer-free solar cells based on CH₃NH₃PbI₃:fullerene blends. The photovoltaic study performed over a series of devices verifies the suitability of this electron transport layer-free strategy as a promising alternative to build efficient solar cells avoiding the use of TiO₂. Furthermore, clear correlation between the LUMO of the fullerene material and the open circuit voltage of the solar cells is found.