Abstract We fabricated electric double-layer transistors comprising large-area WSe₂ monolayers and investigated the effects of electrolyte gating on their photoluminescence (PL) spectra. Using the efficient gating effects of electric double layers, we succeeded in the application of a large electric field (∼10⁷ V cm⁻¹) and the accumulation of high carrier density (>10¹³ cm⁻²). As a result, we observed PL spectra based on both positively and negatively charged excitons and their gate-voltage-dependent redshifts, suggesting the effects of both an electric field and charge accumulation.