Light‐Emitting Electrochemical Cells with Polymer‐Blended InP/ZnSeS Quantum Dot Active Layer
Sangjun Park, Jeehye Yang, Seunghan Kim, Donghyo Hahm, Hyunwoo Jo, Wan Ki Bae, Moon Sung Kang
Abstract
Abstract A light‐emitting electrochemical cell (LEC) is an innovative device with a simple structure wherein a mixture of a luminophore and an electrolyte is sandwiched between electrodes. Here, LECs are presented which contain an active layer composed of green‐emitting InP/ZnSeS quantum dots (QDs) blended with polyvinyl carbozole p‐type polymer semiconductors and 1‐butyl‐3‐methylimidazolium bis(trifluoromethylsulfonyl)imide ionic liquid (IL). The blending of QDs with polymer semiconductors increases the density of holes reaching the QDs; this, in turn, leads to luminescence from QDs, which is unachievable without the presence of polyvinyl carbazole semiconductor. Moreover, the deposition of a zinc oxide nanoparticle layer onto the QD–polymer–IL active layer increases the density of electrons reaching the QDs. The composition of these materials is varied systematically for balancing the injection rates of electron versus hole into the QDs. A luminance of ≈632 cd m −2 and an efficiency of >1.3 cd A −1 are achieved.