Herein, a comprehensive investigation of photoluminescent characteristics of gadolinium oxysulphide (Gd2O2S) phosphors co-doped with erbium (Er3+) and ytterbium (Yb3+) under various excitation wavelengths and varying Yb3+-concentration is reported. Up/downconversion by characteristic Er3+-excited states exhibited a strong visible emission (525 nm, 556 nm, and 668 nm), along with the unusual presence of ultraviolet (UV similar to 360-375 nm) and near-infrared (NIR similar to 800-1000 nm) emissions, simultaneously. Maximum emission intensity in each emission region (visible, UV, NIR) and emission color (i.e., violet, green, pink, magenta, yellow, orange, red) is modulated by tuning Yb3+-doping concentration for different excitation wavelengths. The spectral engineering obtained under various incident photon energies (285 nm, 380 nm, 450 nm, 808 nm, 980 nm, and 1064 nm) is explained via multiple optical transition routes between Er3+ and Yb3+ ions. This Gd2O2S: Er, Yb (GOS) phosphor having manifold excitation and emission avenues, high immunity against ambient degradation and no toxicity, is actively proposed as an efficient energy converter for increased solar energy harvesting.