title: Improving performance and lifetime of small-molecule organic photovoltaic devices by using bathocuproine-fullerene cathodic layer.
abstract: In this study, we compared the use of neat bathocuproine (BCP) and BCP:C60 mixed buffer layers in chloroboron subphthalocyanine (SubPc)/C60 bilayer organic photovoltaic (OPV) devices and analyzed their influence on device performance. Replacing the conventional BCP with BCP:C60 enabled manipulating the optical field distribution for optimizing the optical properties of the devices. Estimation of the interfacial barrier indicated that the insertion of the BCP:C60 between the C60 and electrode can effectively reduce the barrier for electrons and enhance electron collection at the electrode. Temperature-dependent measurements of the OPV devices performed to calculate the barrier height at the SubPc/C60 interface suggested that band bending was larger when the BCP:C60 buffer layer was used, reflecting increased exciton dissociation efficiency. In addition, the device lifetime was considerably improved when the BCP:C60 buffer layer was used. The device performance was stabilized after the photodegradation of the active layers, thereby increasing the device lifetime compared with the use of the neat BCP buffer layer. Atomic force microscopy images showed that the neat BCP was easily crystallized and could degrade the cathodic interface, whereas the blend of C60 and BCP suppressed the crystallization of BCP. Therefore, the optimal buffer layer improved both the device performance and the device lifetime.
authors: †Department of Electronic Engineering, Ming Chi University of Technology, No. 84, Gungjuan Road, Taishan District, New Taipei City 24301, Taiwan.
authors: Shun-Wei
authors: SW
authors: Liu
authors: ‡Department of Electronic Engineering, National Taiwan University of Science and Technology, No. 43, Section 4, Keelung Road, Daan District, Taipei 10607, Taiwan.
authors: Chih-Chien
authors: CC
authors: Lee
authors: ‡Department of Electronic Engineering, National Taiwan University of Science and Technology, No. 43, Section 4, Keelung Road, Daan District, Taipei 10607, Taiwan.
authors: Wei-Cheng
authors: WC
authors: Su
authors: ‡Department of Electronic Engineering, National Taiwan University of Science and Technology, No. 43, Section 4, Keelung Road, Daan District, Taipei 10607, Taiwan.
authors: Chih-Hsien
authors: CH
authors: Yuan
authors: †Department of Electronic Engineering, Ming Chi University of Technology, No. 84, Gungjuan Road, Taishan District, New Taipei City 24301, Taiwan.
authors: Yi-Sheng
authors: YS
authors: Shu
authors: ‡Department of Electronic Engineering, National Taiwan University of Science and Technology, No. 43, Section 4, Keelung Road, Daan District, Taipei 10607, Taiwan.
authors: Wen-Chang
authors: WC
authors: Chang
authors: †Department of Electronic Engineering, Ming Chi University of Technology, No. 84, Gungjuan Road, Taishan District, New Taipei City 24301, Taiwan.
authors: Jhih-Yan
authors: JY
authors: Guo
authors: †Department of Electronic Engineering, Ming Chi University of Technology, No. 84, Gungjuan Road, Taishan District, New Taipei City 24301, Taiwan.
authors: Chien-Feng
authors: CF
authors: Chiu
authors: †Department of Electronic Engineering, Ming Chi University of Technology, No. 84, Gungjuan Road, Taishan District, New Taipei City 24301, Taiwan.
authors: Ya-Ze
authors: YZ
authors: Li
authors: †Department of Electronic Engineering, Ming Chi University of Technology, No. 84, Gungjuan Road, Taishan District, New Taipei City 24301, Taiwan.
authors: Tsung-Hao
authors: TH
authors: Su
authors: ‡Department of Electronic Engineering, National Taiwan University of Science and Technology, No. 43, Section 4, Keelung Road, Daan District, Taipei 10607, Taiwan.
authors: Kuan-Ting
authors: KT
authors: Chen
authors: †Department of Electronic Engineering, Ming Chi University of Technology, No. 84, Gungjuan Road, Taishan District, New Taipei City 24301, Taiwan.
authors: Po-Chien
authors: PC
authors: Chang
authors: †Department of Electronic Engineering, Ming Chi University of Technology, No. 84, Gungjuan Road, Taishan District, New Taipei City 24301, Taiwan.
authors: Tzu-Hung
authors: TH
authors: Yeh
authors: ‡Department of Electronic Engineering, National Taiwan University of Science and Technology, No. 43, Section 4, Keelung Road, Daan District, Taipei 10607, Taiwan.
authors: Yu-Hsuan
authors: YH
authors: Liu
keywords: cathodic buffer layer; lifetime; morphology; optical manipulation; power conversion efficiency; small-molecule organic photovoltaic