The functional properties of cuprates are strongly determined by the doping state and carrier density. We present an oxygen doping study of YBa2Cu3O7-δ (YBCO) thin films from underdoped to overdoped state, correlating the measured charge carrier density, nH, the hole doping, p, and the critical current density, Jc. Our results show experimental demonstration of strong increase of Jc with nH, up to Quantum Critical Point (QCP), due to an increase of the superconducting condensation energy. The ultra-high Jc achieved, 90 MA cm−2 at 5 K corresponds to about a fifth of the depairing current, i.e. a value among the highest ever reported in YBCO films. The overdoped regime is confirmed by a sudden increase of nH, associated to the reconstruction of the Fermi-surface at the QCP. Overdoping YBCO opens a promising route to extend the current carrying capabilities of rare-earth barium copper oxide (REBCO) coated conductors for applications.