An efficient on-chip inductor-less switching power converter for solar energy harvesting is presented. The new energy-efficient switching power converter improves the charge transfer capability as well as charge sharing time from the harvester to the load. We also present an analytical model to estimate the optimal parameters for maximizing the system efficiency. The proposed interface circuits have been designed using 0.18-μm CMOS technology node, and the circuit simulations demonstrate that the proposed strategy offers a system efficiency of 70% under three different light conditions.