  We consider a line-shape of magnetoexciton photoluminescence from quantum
wells when the disorder is sufficiently small. In this case the phonon-assisted
optical transitions become important for the line formation. We study both
inter-band and intra-band excitons. For inter-band excitons the width of a
single peak emission line is calculated as a function of temperature and
quantum well width. For intra-band excitons the double peak of the emission
line is predicted when the electron filling factor is odd and greater or equal
to three. In the latter case the lowest magnetoexciton dispersion curve has a
minimum at non-zero momentum. Then the higher-energy peak results from the
direct optical emission of zero-momentum excitons. The origin of the
lower-energy peak is the phonon-assisted transitions from the non-zero momentum
exciton states. With increasing temperature, the higher-energy peak becomes
more pronounced and the lower-energy peak vanishes.
