卒業生（SイノベGr.・夫研）の春日恒祐君 (Mr. Kosuke Kasuga) の塗布タンデム素子の中間接続層の動作挙動を評価した「Operation behaviors of interconnecting-layers in solution-processed tandem organic light-emitting devices」と題する研究論文が Elsevier の Organic Electronics (IF: 3.680) に受理・掲載されました。当研究室から初めて順構造塗布型タンデム素子の研究が発表されましたが、その中間接続層の動作機構については明らかでない部分が多くありました。本研究では、塗布中の材料の下層への拡散、加熱による電荷発生性能の向上が、中間接続層が良好に機能するために必要であることをデバイスの動作挙動評価および電子顕微鏡観察から明らかにしました。
By Satoru Ohisa, Kosuke Kasuga, Kohei Endo, Yong-Jin Pu*, Takayuki Chiba, Junji Kido,*
Organic Electronics, 63, 98-103 (2018).
Abstract: We investigated the operation behaviors of solution-processed tandem organic-light-emitting devices with regular structures. We fabricated devices with interconnecting-layers of ZnO nanoparticles (NPs)/polyethyleneimine ethoxylated (PEIE)/phosphomolybdic acid (PMA)/poly[(9,9-dioctylfluorenyl-2,7-diyl)-co-(4,4'-(N-(4-sec-butylphenyl) diphenylamine)) (TFB), which were sandwiched by electrodes. Charges were generated at the PMA/TFB interface under electric fields instead of being injected from electrodes. Thermal baking effects of each layer were investigated. We found that high-temperature baking of PMA was essential for realizing low driving voltages. Acetonitrile solvent, which is a good solvent for underlayer PEIE, of PMA solution was replaced with n-butylacetate, which is a poor solvent for underlayer PEIE, to investigate the effect of the mixing state of the PEIE/PMA interface. The device with PMA from n-butylacetate showed significantly larger driving voltage than that with PMA from acetonitrile. The mixing of PEIE and PMA is also essential for realizing low driving voltage. Observation results of the cross-sections of the films by transmission electron microscope supported these conclusions.
