The band energy diagram of PCBM–DH6T bulk heterojunction solar cells: synchrotron-induced photoelectron spectroscopy on solution processed DH6T:PCBM blends and in situ prepared PCBM/DH6T interfaces
- 23 October 2013
- journal article
- research article
- Published by Royal Society of Chemistry (RSC) in Journal of Materials Chemistry C
- Vol. 1 (45), 7635-7642
- https://doi.org/10.1039/c3tc31745e
Abstract
Applying high resolution synchrotron-induced photoelectron spectroscopy (SXPS), the electronic properties of a bulk heterojunction (BHJ) model solar cell consisting of phenyl-C61-butyric-acid-methyl-ester (PCBM) as an acceptor and α,ω-dihexylsexithiophene (DH6T) as a donor are investigated. This donor material can be prepared via UHV thermal evaporation and solution based techniques. Samples prepared by either technique show identical core levels and valence band spectra proving the equivalency of the resulting electronic properties. The formation of the PCBM/DH6T interface is studied in an in situ experiment based on stepwise evaporation of DH6T onto PCBM. The deposition of donor–acceptor mixed solutions leads to phase separated bulk heterojunction layers with a donor cap. The combination of SXPS measurements on a series of ex situ prepared blend films from solutions with varying donor–acceptor concentrations with in situ interface formation experiments enables deriving the band diagram across the bulk heterojunction and into the donor cap. Band bending of up to 0.3 eV is induced in the DH6T cap layer and a dipole of 0.26 eV forms at the PCBM:DH6T bulk heterojunction. The direction of the band bending leads to hole accumulation on the donor side of the interface, which may increase recombination with transferred electrons in the acceptor and thereby negatively affects the device performance.This publication has 37 references indexed in Scilit:
- Synchrotron induced photoelectron spectroscopy on drop casted donor/acceptor bulk heterojunction: Orbital energy line up in DH6T/PCBM blendsSurface Science, 2013
- Electronic structure of the pentacene–gold interface: A density-functional theory studyOrganic Electronics, 2009
- Engineering the electronic structure of the CuPc/BPE‐PTCDI interface by WO3 doping of CuPcPhysica Status Solidi (a), 2009
- Vertical Phase Separation in Poly(3‐hexylthiophene): Fullerene Derivative Blends and its Advantage for Inverted Structure Solar CellsAdvanced Functional Materials, 2009
- Energy‐Level Alignment at Organic/Metal and Organic/Organic InterfacesAdvanced Materials, 2009
- Morphology evolution via self-organization and lateral and vertical diffusion in polymer: fullerene solar cell blendsNature Materials, 2008
- Photoelectron Spectroscopy at the Solid–Liquid Interface of Dye–Sensitized Solar Cells: Unique Experiments with the Solid–Liquid Interface Analysis System SoLiAS at BESSYChimia, 2007
- Formation of the Interfacial Dipole at Organic‐Organic Interfaces: C60/Polymer InterfacesAdvanced Materials, 2007
- Influence of alkyl chain substitution on sexithienyl-metal interface morphology and energeticsApplied Physics Letters, 2006
- Atomic subshell photoionization cross sections and asymmetry parameters: 1 ⩽ Z ⩽ 103Atomic Data and Nuclear Data Tables, 1985