The paper presents a method for calculating the optimal parameters of the front contact grid of photovoltaic converters (PC). This method extends a previously developed tube model of current spreading and allows taking into  account the thickness, height, and resistivity of the contact fingers, as well as shading effects on the photoactive surface. The method was applied to high-efficient AlGaAs/GaAs photovoltaic converters of laser radiation (λ = 800–850  nm) fabricated with different front metal grid in which contact pitch varied from 100 to 140 μm. Results show that the improved model precisely describes the experimental current-voltage (I–V) curves of all PCs. Reducing the metal finger height to 4 μm increases efficiency by 1.1% for the PC with 140 μm contact pitch and by 0.7% for the one with 100 μm contact pitch.