Effect of 2-D Delocalization on Charge Transport and Recombination in Bulk-Heterojunction Solar Cells

Ronald Österbacka*, Almantas Pivrikas, Gytis Juška, Andrius Poškus, Harri Aarnio, Gytis Sliaužys, Kristijonas Genevičius, Kestutis Arlauskas, Niyazi Serdar Sariciftci

*Corresponding author for this work

Research output: Contribution to journalArticleScientificpeer-review

19 Citations (Scopus)

Abstract

Charge-carrier transport and recombination in thermally treated and untreated films of poly(3-hexylthiophene) (P3HT) and 1-(3-methoxycarbonyl) propyl-1-phenyl-[6,6]-metha-nofullerene (PCBM) bulk-heterojunction solar cells (BHSCs) have been measured using various electrooptical techniques. The formation of lamellar structure in P3HT has a large effect on the efficiency, carrier transport, and recombination of photogenerated charge carriers. Treated P3HT/PCBM solar cells show greatly reduced carrier recombination compared to what is typically expected in low-mobility materials and electric-field- independent carrier generation. In untreated films, the recombination is close to Langevin-type with electric-field-dependent quantum efficiency, consistent with the typically observed Onsager-type generation. Furthermore, we observe an increased effective capacitance in treated films, consistent with increased charge screening. The importance of the interface between the lamellar structured P3HT and PCBM is evident from optical spectroscopies showing that 2-D polarons are directly generated using sub-gap excitation. We conclude that the formation of lamellar structures in the polymer donor, and subsequent, delocalization of the charges is favorable for making efficient BHSCs.

Original languageEnglish
Article number5497067
Pages (from-to)1738-1745
Number of pages8
JournalIEEE Journal on Selected Topics in Quantum Electronics
Volume16
Issue number6
DOIs
Publication statusPublished - Nov 2010
MoE publication typeA1 Journal article-refereed

Keywords

  • Organic compounds
  • photovoltaic cell materials
  • photovoltaic cells
  • physics

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