Directed Vertical Diffusion of Photovoltaic Active Layer Components into Porous ZnO‐Based Cathode Buffer Layers. Issue 15 (2nd March 2018)

• Record Type: Journal Article
• Authors: Kang, Jia‐Jhen; Yang, Tsung‐Yu; Lan, Yi‐Kang; Wu, Wei‐Ru; Su, Chun‐Jen; Weng, Shih‐Chang; Yamada, Norifumi L.; Su, An‐Chung; Jeng, U‐Ser
• Is Part Of: Small. Volume 14:Issue 15(2018)
• Page Start: n/a
• Page End: n/a
• Publication Date: 2018-03-02
• Subjects: neutron and anomalous X‐ray reflectivity -- polymer solar cells -- scattering contrast variation -- vertical composition profile -- ZnO‐based cathode buffer layer; Nanotechnology -- Periodicals; Nanoparticles -- Periodicals; Microtechnology -- Periodicals; 620.5
• DOI: 10.1002/smll.201704310
• Languages: English
• ISSNs: 1613-6810

Abstract

Abstract: Cathode buffer layers (CBLs) can effectively further the efficiency of polymer solar cells (PSCs), after optimization of the active layer. Hidden between the active layer and cathode of the inverted PSC device configuration is the critical yet often unattended vertical diffusion of the active layer components across CBL. Here, a novel methodology of contrast variation with neutron and anomalous X‐ray reflectivity to map the multicomponent depth compositions of inverted PSCs, covering from the active layer surface down to the bottom of the ZnO‐based CBL, is developed. Uniquely revealed for a high‐performance model PSC are the often overlooked porosity distributions of the ZnO‐based CBL and the differential diffusions of the polymer PTB7‐Th and fullerene derivative PC71 BM of the active layer into the CBL. Interface modification of the ZnO‐based CBL with fullerene derivative PCBEOH for size‐selective nanochannels can selectively improve the diffusion of PC71 BM more than that of the polymer. The deeper penetration of PC71 BM establishes a gradient distribution of fullerene derivatives over the ZnO/PCBE‐OH CBL, resulting in markedly improved electron mobility and device efficiency of the inverted PSC. The result suggests a new CBL design concept of progressive matching of the conduction bands. Abstract : A methodology of contrast variation with neutron and anomalous X‐ray reflectivity is developed to map the multicomponent depth compositions of an inverted polymer solar cell, from the active layer surface down to the bottom of the porous ZnO–C60 cathode buffer interlayer. Facilitated by size‐selective ZnO–C60 nanochannels, PC71 BM diffusion from the active layer builds a gradient distribution throughout the interlayer.