| Abstract [eng] |
Organic light emitting diodes (OLED) are becoming increasingly popular in smartphone and TV screens due to unmatched contrast, high resolution, vibrant colors and unique designs. One of the most auspicious OLED emitter strategy utilizes thermally assisted delayed fluorescence (TADF) to harvest 100 % of injected electrons. Despite the appealing properties of TADF emitters the technology is yet to be commercialized as the science behind it is still young and some unsolved issues remain. The aim of this work was to investigate how various molecular modifications impact TADF properties and suggest some optimization pathways to achieve stable and efficient blue emission. In the first part of the thesis the effects of conformational disorder in solid-state were analyzed and designing a rigid molecular core or increasing reverse intersystem crossing rate was offered as solution to minimize its effects. In the second part donor and acceptor moieties were bound by hyperconjugated σ-bridge. In-depth analysis revealed unexpected interplay of intra-/intermolecular charge transfer states as the origin of dual emission. Lastly, some donor-acceptor compounds were optimized by molecular modifications to produce efficient (up to 29 % external quantum efficiency) green, cyan and blue OLED devices. Also, TADF decay lifetime of 860 ns was achieved which is amongst the lowest values reported for TADF emitters. |
