Surface defects impeded excitons in Alq3 based hetero junction OLEDs

► Alq3 film fabricated on quartz and TPD/ITO with very low RMS of 0.74 and 0.37 nm, respectively. ► Effect of pin holes on PL emission spectrum of Alq3 and TPD/Alq3 hetero junctions observed. ► Maximum current efficiency of 5 cd/A have been achieved for Alq3 HJOLED without any buffer layers. ► Maximum brightness of 1.02 × 104 cd/m2 have been achieved for the HJOLED at optimized rate.