title: Stacking multiple connecting functional materials in tandem organic light-emitting diodes.
abstract: Tandem device is an important architecture in fabricating high performance organic light-emitting diodes and organic photovoltaic cells. The key element in making a high performance tandem device is the connecting materials stack, which plays an important role in electric field distribution, charge generation and charge injection. For a tandem organic light-emitting diode (OLED) with a simple Liq/Al/MoO3stack, we discovered that there is a significant current lateral spreading causing light emission over an extremely large area outside the OLED pixel when the Al thickness exceeds 2 nm. This spread light emission, caused by an inductive electric field over one of the device unit, limits one's ability to fabricate high performance tandem devices. To resolve this issue, a new connecting materials stack with a C60fullerene buffer layer is reported. This new structure permits optimization of the Al metal layer in the connecting stack and thus enables us to fabricate an efficient tandem OLED having a high 155.6 cd/A current efficiency and a low roll-off (or droop) in current efficiency.
authors.affiliation: Department of Physics, Yunnan University, Kunming, Yunnan 650091, People's Republic of China.|Yunnan Key Laboratory for Micro/Nano Materials and Technology, Yunnan University, Kunming, Yunnan 650091, People's Republic of China.
authors.forename: Tao
authors.initials: T
authors.lastname: Zhang
authors.affiliation: Department of Physics, Yunnan University, Kunming, Yunnan 650091, People's Republic of China.|Yunnan Key Laboratory for Micro/Nano Materials and Technology, Yunnan University, Kunming, Yunnan 650091, People's Republic of China.
authors.forename: Deng-Ke
authors.initials: DK
authors.lastname: Wang
authors.affiliation: Department of Physics, Yunnan University, Kunming, Yunnan 650091, People's Republic of China.|Yunnan Key Laboratory for Micro/Nano Materials and Technology, Yunnan University, Kunming, Yunnan 650091, People's Republic of China.
authors.forename: Nan
authors.initials: N
authors.lastname: Jiang
authors.affiliation: Department of Physics, Yunnan University, Kunming, Yunnan 650091, People's Republic of China.|Yunnan Key Laboratory for Micro/Nano Materials and Technology, Yunnan University, Kunming, Yunnan 650091, People's Republic of China.|Department of Materials Science and Engineering, University of Toronto, Toronto, Ontario M5S 3E4, Canada.
authors.forename: Zheng-Hong
authors.initials: ZH
authors.lastname: Lu