Optical Properties of Crystalline Thin Films of the Organic Laser Gain Material 4,4'-Bis[(N-carbazole)styryl]biphenyl

Enhancing photoluminescence quantum yield and excellent transport associated with molecular order are important for advancing organic laser device performance. However, materials combining excellent quantum yield and transport are rare. 4,4'-Bis[(N-carbazole)styryl]biphenyl (BSB-Cz) has been heavily investigated as a promising material for laser devices. However, research on highly ordered BSB-Cz crystalline films is lacking, despite the much better transport properties to be expected. Here, we show that BSB-Cz thin-film crystals can be prepared using a simple vacuum deposition method, followed by thermal annealing. The resulting crystalline neat BSB-Cz thin films show a very high photoluminescence quantum yield of over 85% and superior optical stability compared to amorphous BSB-Cz films under intense pumping conditions. We believe that our work provides a route for advancing organic laser devices through introducing crystallinity in emitter thin films with a scalable approach.