Improving charge carrier balance by incorporating additives in the active layer

Light-emitting electrochemical cells (LECs) have recently drawn much research interest because of their advantages related to single-layered device architecture, low-bias operation, and employing inert electrodes. Such features enable LECs to be inexpensive and efficient organic light-emitting devices. As mentioned in Chap. 1, the lack of charge injection and transporting layers hinders to achieve balanced carrier mobilities in single-layered LECs. In this chapter, techniques reported in literatures to achieve charge carrier balance in LECs by incorporating additives in the active layer are carefully reviewed. Furthermore, a new optical technique to probe charge carrier balance in LECs is introduced to confirm the effect attributed to the use of additives. This chapter summarizes that improving charge carrier balance of LECs would be essential to realize high device efficiency in spite of the existence of electrochemically doped layers.