Suppressing the Surface Recombination and Tuning the Open-Circuit Voltage of Polymer/Fullerene Solar Cells by Implementing an Aggregative Ternary Compound

D. Galli, N. Gasparini, M. Forster, A. Eckert, C. Widling, M.S. Killian, A. Avgeropoulos, V.G. Gregoriou, U. Scherf, C.L. Chochos, C.J. Brabec, T. Ameri

Research output: Contribution to journalArticlepeer-review

Abstract

In this work, we present a novel small molecule based on dithienylthienothiadiazole units (named SM1) acting as an efficient component in ternary blend organic solar cells to modify the hole extraction at the interface. Our findings show that the SM1 suppresses the surface recombination and enhances the open-circuit voltage (Voc). By introducing SM1 in a host system composed of poly(3-hexylthiophene) (P3HT) and [6,6]-phenyl-C61-butyric acid methyl ester (PCBM), we obtained Voc values of up to 0.75 V and fill factors larger than 70% for the ternary blends. As a consequence, the power conversion efficiency is improved by about 30% compared to P3HT:PCBM binary devices. Interestingly, external quantum efficiency and absorption spectra in the near-infrared region do not show any contribution of SM1 in dried films. Instead, the addition of the small molecule improves the Voc by reducing the surface recombination losses. To shed light on the recombination processes, we carried out Fourier-transform photocurrent spectroscopy and impedance spectroscopy measurements. This work shows that the ternary concept can also have functionalities other than photosensitization and can even act as a morphology-directing agent or an interface modifier. © 2018 American Chemical Society.
Original languageEnglish
Pages (from-to)28803-28811
Number of pages9
JournalACS Applied Materials and Interfaces
Volume10
Issue number34
DOIs
Publication statusPublished - 2018

Keywords

  • Butyric acid
  • Efficiency
  • Molecules
  • Open circuit voltage
  • Organic solar cells
  • Timing circuits
  • External quantum efficiency
  • Impedance spectroscopy measurements
  • Poly-3-hexylthiophene
  • Power conversion efficiencies
  • Recombination process
  • Surface recombination loss
  • Surface recombinations
  • [6
  • 6]-phenyl-C61-butyric acid methyl esters
  • Solar cells

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