Using a spinning polymer layer of poly(N-vinylcarbazole)(PVK) as hole transport layer(HTL) and an evaporated layer of tris(8-hydroxy)quinoline aluminum(Alq_3) as electron transport layer and emission layer,the organic light-emitting diodes(OLEDs) with the structure of ITO/PVK/Alq_3/Mg∶Ag/Al have been fabricated.By measuring and analyzing the current-voltage-brightness characteristics,influences of the thickness of HTL on device performance have been investigated.The experimental results show that optical an...