We report photoluminescence emission from single self-assembled InAlGaAs quantum dots, which is broadened purely by dephasing processes. We observe linewidths as low as 6+/-3@meV at 10K, which agrees with the homogeneous linewidth derived from four-wave mixing experiments. By selecting dots that are not affected by local field fluctuations and using high-energy excitation, we avoid additional sources of linewidth broadening typically present in single-dot photoluminescence spectra. We observe a strong LO-phonon coupling in InAlGaAs and InGaAs dots, which becomes the dominating contribution to the linewidth above 50K.