Conventionally, solar cells used asymmetric doping (p-n or p-i-n junction) for charge carrier separation and collection. However, these doped solar cell structures are limited by several optoelectronic losses as well as technological limitations specific to the fabrication of these doped structures. We try to solve this problem by using a charge carrier selective contact which achieve charge carrier separation based on the band bending at the interface. These charge carrier selective layers reduce the recombination at the contact and improve passivation. Some of the major requirements for selective contacts include high transparency, high mobility, and tuneable Fermi level. We first use simulations to design the structure and optimize the charge carrier selective contacts for thin film and nanowire III-V (GaAs and InP) heterojunction solar cells. For these materials, we investigate ZnO and CuI as the electron and hole selective contact, respectively. SCAPS-1D is used for optoelectronic simulation of thin films, whereas, for nanowire optical and electronic simulation, we use Lumerical FDTD and Lumerical Device modules, respectively. We then grow and fabricate these solar cells, and the experimental results are used to validate the simulation results.Based on optimized simulation parameters we fabricate devices with electron or hole selective contacts. Currently, have demonstrated an efficiency of 18.12% with one of the highest reported Voc of 819 mV for InP solar cells using ZnO as the electron selective contacts. In this presentation I will also show the preliminary results for CuI as the hole contact and outline the plan for extending these studies to nanowire solar cells.