Optoelectronic characteristics of MEH-PPV polymer LEDs with n-a-SiCGe:H and p-a-Si:H carrier injection layers

The conventional organic hole/electron injection layer (HIL/EIL) in an MEH-PPV polymer LED (PLED) has been replaced with a p-a-Si:H/n-a-SiCGe:H layer, respectively, to investigate the feasibility of combining polymer and inorganic films for LED fabrication. With 6 nm p-a-Si:H HIL and 60 nm MEH-PPV emitting layers, the device with a 17 nm n-a-SiCGe EIL (deposited without intentional substrate heating) had a threshold voltage (V_th) of 21.2 V and a brightness of 404.5 cd/m² at an injected current density (J) of 0.6 A/cm². The device V_th and brightness could be further improved to 14.3 V and 6450 cd/m² (under J = 0.3 A/cm² only), respectively, by increasing the Ge content in the EIL appropriately. The experimental results indicate that using the inorganic doped amorphous semiconductors as HIL/EIL of PLEDs is feasible and the obtained PLED characteristics are affected significantly by the films employed.