This paper explores how different layers in an organic light emitting diode (OLED) impacts its performance. Here, different layers of OLED similar to hole/electron injection layer, transport layer, and block layers are analyzed. Four experimental devices are taken into consideration and their results are compared to one over another to analyze the impact of every layer. Inside depth analysis is also performed on the device to inspect what really is happening Innermost of the OLED. It is noticed that hole and electron block layer are instrumental in improving the device luminescence performance and effificiency. There is an improvement of 16, 37 and 38% in the luminescence of the device when hole block layers and electron block layers are added. Internal device analysis reveals that increase in charge carrier concentration and carrier confifinement are the reason for this improvement.
Organic electronics, in the past decades, has been the choice of researchers to complement the conventional silicon-based technology. These devices are being preferred because of the fact that they are lightweight (Chou et al. 2017), thin, flflexible, easy to fabricate with a low-cost (Chou et al. 2017; Kumar et al. 2014; Fu et al. 2016) involved in manufacturing. Because of this intense research, recent times have seen different applications based on organic transistors, like memory and digital circuits, which have shown good performance. Because of this improvement other applications like OLED, RFID etc. are also emerging and improving.
Currently, OLED is being used by companies like Apple and LG for the display application. Still, a number of researchers are trying to further enhance its performance. Different strategies are being followed to improve the performance of OLED. Some of them are static in the sense that these will work in a specifific way like a material design (Malliaras et al. 2001; Chan et al. 2001; Wen et al. 2005), which will work with a specifific set of materials only. Others are dynamic like the use of block layers in architecture (Yang et al. 2006) and change of electrode material (Wu et al. 2007) in which, depending on the architecture different materials can be used. Herein, the work carried out is related to the latter aspect wherein different materials can be used in OLED architecture to enhance its performance. Various analyses of different layers in a multilayered OLED architecture are provided wherein; these analyses cover how these different layers help in enhancing OLED performance.
Fig3
HOMO and LUMO level of OSC plays an important role in charge carrier injection. If these levels are matched with the work-function of adjacent electrode then charge injection in the OLED will improve which will result in higher charge carriers and ultimately recombination. HIL (Park et al. 2007) and EIL (Park et al. 2009) layers are used for this purpose. These layers are selected depending on their orbital levels, i.e. HOMO for HIL and LUMO for EIL and matching of these levels to the work function of respective electrodes. The closer these two levels are, the better is the charge injection. These layers help more and more charge carriers to reach respective transport layers as the energy barrier is reduced between transport layers and electrode work-function. This is shown in energy band diagram given in Fig. 3. Thus better charge injection improves the recombination rate.
In this paper, the impact of different layers on the performance of has been analyzed. It is known that the performance of multilayered OLED is better in compared to single and double layer OELD. This improvement in performance is due to the different layers included in its architecture. Four devices are compared in this paper, starting form multilayered device, Device A (consisting of HIL, EIL, and EML) and thereafter, hole block layer and electron block layers are added in Device B (single HBL), Device C (double HBL) and Device D (change in HIL, to EBL). When these devices are analyzed it was found out that compared to Device A, there is 16, 37 and 38% improvement in luminescence properties for Device B, C, and D respectively. Furthermore, the luminescence power effificiency for these devices turns out to be 6.73, 11.32, 11.70 and 11.34 (Device A–D) respectively.
