Abstracts:Although organometal halide perovskites are emerging as emitters with extremely high color purity and low cost, device performances are significantly restricted by poor morphology of the perovskite layer. In this work, a multi-step spin-coating method is used to prepare CH3NH3PbBr3 perovskite layer, which a dense and uniform perovskite film with small grain sizes and a ∼100% coverage. Moreover, the component of the hole injection layer poly(3,4-ethylenedioxythio- phene):poly(4-styrenesulphonate) (PEDOT:PSS) adjusted with PSS is applied to reduce the injection barrier between PEDOT:PSS and perovskite layer. With above-mentioned approaches, efficient perovskite light-emitting diodes with maximum luminance and current efficiency of 9900 cd m⁻² and 2.6 cd A⁻¹ are eventually acquired.

Abstracts:Carrier transport behavior in organic light emitting diode (OLED) is visualized by Modulus spectroscopy using typical layered devices ITO/α-NPD/Alq3/LiF/Al. Two techniques of Modulus analysis, Dynamic Modulus Plot (DMP) and Distributed Circuit Element (DCE) analysis are presented. The hole distribution in NPD layer is visualized by DCE model. The DMP and the DCE model show that the hole and electron transport in NPD/Alq3 devices up to 10 mA/cm² obey not to a space charge limited current but an Ohmic conduction. It is well known that holes accumulate in NPD even below the turn-on voltage of DC current. This hole accumulation depends on both of NPD and Alq3 layer thicknesses. The voltage dependence is scaled by the Alq3 thickness, whereas the carrier density dependence by the NPD thickness. We propose a model that the accumulated holes are supplied by the thermal activation of the finite number of shallow trap sites localizing at ITO/NPD interface.