Charge generation layer with octylamine assistant layer for efficient tandem organic light-emitting diodes

Tandem organic light-emitting diodes (OLEDs) entail the insertion of efficient charge-generating layers (CGLs) between tandem light-emitting units. In this work, CGLs with octylamine (OTA) layers were prepared and device performance was analyzed with OTA thickness. The best electrical and optical performance was obtained for the tandem devices at an OTA thickness of 7 nm, with a maximum brightness of 22,080 cd/m2. The OTA solves the problem of the spin-coating operation to dissolve the underlying organics and enhances the charge generation and injection capability of the CGL. The current efficiency of tandem OLED devices fabricated using OTA/P3HT: PC61BM/NPB: F4-TCNQ as CGL was improved 2.5 times. More importantly, the Finite Difference Time Domain (FDTD) simulations provide the basis for experimental phenomena. The device with added OTA layer has a larger internal electric field strength, which can speed up the carrier movement and improve the composite efficiency. Meanwhile, with the increase of OTA film thickness, the spectrum approaches the reference device. It is expected for us to open up an effective way to fabricate high-efficiency tandem OLED devices.