We have seen the effects of buffer layer in organic light-emitting diodesusing poly(N-vinylcarbazole)(PVK). Polymer PVK buffer layer was made using static spin-casting method. T재 device structures were made; one is LYO/TPD/Alq3/Al as areference and the other is ITO/PVK/Alq3/Al to see the effects of buffer layer in organic light-emitting diodes. Current-voltage characteristics, luminance-voltage characteristics and luminous effciency were measured with a variation of spin-casting speeds. We have obtained an improvement of luminous efficiency by a factor of two andhalf when the PVK buffer layer is used.