The performance of an organic-inorganic perovskite solar cell (PSC) can be enriched via sinking the losses arisen in it. These losses are signified by the photovoltaic (PV) cell parameters (photogenerated current density (J(ph)), shunt resistance (R-sh), series resistance (R-s), diode ideality factor (n), and reverse saturation current density (J(0))). In this paper, the dependency of the PV cell parameters of the Cu-doped nickel oxide (NiO:Cu)-based PSCs was investigated as a function of the Cu-doping (R-Cu/Ni) and the annealing temperature (t(an)). The maximum value of J(ph) was obtained for R-Cu/Ni = 5% and t(an) = 400 degrees C. Moreover, the R-sh value enhanced by increasing R-Cu/Ni and t(an), while the R-s was decreased with the increase of the annealing temperature with the minimal value attained at R-Cu/Ni and t(an) of 5% and 400 degrees C, respectively. Both n and J(0) increased with the rise in R-Cu/Ni and t(an). Electrical measurements showed that PSC fabricated using 5% NiO:Cu-HTL annealed at 400 degrees C exhibits the highest PV performance with a short-circuit current density (J(sc)) of 21.24 mA/cm(2), an open-circuit voltage (V-oc) of 1.031 V, a fill factor (FF) of 72.50% and a power conversion efficiency (eta) of 15.88%. The corresponding values of J(ph), R-sh, R-s, n and J(0) are 21.31 mA/cm(2), 1042.69 Omega.cm(2), 3.265 Omega.cm(2), 1.9739 and 3.025 x 10(-11) A/cm(2), respectively. These encouraging results provide the possibility to further optimize the optical and electrical properties of NiO:Cu-HTLs and pave the way for the development of more stable and highly-efficient PSCs.