We have studied the low-temperature photoluminescence (PL) of the self-assembled InAs single quantum dots (QDs) using conventional micro-PL setup to detect PL from an individual QD. It is demonstrated, that at certain experimental conditions, what concerns the laser excitation energy, the laser power and the crystal temperature, several additional lines, redshifted relative to the ground state transition, appear in the PL spectra. These are interpreted in terms of charged exciton complexes which form due to the population of quantum dots with a nonequal amount of electrons and holes. The latter phenomenon is determined by the excess energies of photogenerated carriers and is proposed as an effective optical method to create and study charged exciton complexes in QDs.