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Efficient singlet exciton fission in pentacene prepared from a soluble precursor

DOI: 10.1063/1.4968518 DOI Help

Authors: Maxim Tabachnyk (University of Cambridge) , Arfa H. Karani (University of Cambridge) , Katharina Broch (University of Cambridge; Fritz-Haber Institut der Max-Planck-Gesellschaft) , Luis M. Pazos-outón (University of Cambridge) , James Xiao (University of Cambridge) , Tom C. Jellicoe (University of Cambridge) , Jiri Novak (Masaryk University) , David Harkin (University of Cambridge) , Andrew J. Pearson (University of Cambridge) , Akshay Rao (University of Cambridge) , Neil C. Greenham (University of Cambridge) , Marcus L. Böhm (University of Cambridge) , Richard H. Friend (University of Cambridge)
Co-authored by industrial partner: No

Type: Journal Paper
Journal: Apl Materials , VOL 4

State: Published (Approved)
Published: November 2016

Open Access Open Access

Abstract: Carrier multiplication using singlet exciton fission (SF) to generate a pair of spin-triplet excitons from a single optical excitation has been highlighted as a promising approach to boost the photocurrent in photovoltaics (PVs) thereby allowing PV operation beyond the Shockley-Queisser limit. The applicability of many efficient fission materials, however, is limited due to their poor solubility. For instance, while acene-based organics such as pentacene (Pc) show high SF yields (up to200%), the plain acene backbone renders the organic molecule insoluble in common organic solvents. Previous approaches adding solubilizing side groups such as bis(tri-iso-propylsilylethynyl) to the Pc core resulted in low vertical carrier mobilities due to reduction of the transfer integrals via steric hindrance, which prevented high efficiencies in PVs. Here we show how to achieve good solubility while retaining the advantages of molecular Pc by using a soluble precursor route. The precursor fully converts into molecular Pc through thermal removal of the solubilizing side groups upon annealing above 150 °C in the solid state. The annealed precursor shows small differences in the crystallinity compared to evaporated thin films of Pc, indicating that the Pc adopts the bulk rather than surface polytype. Furthermore, we identify identical SF properties such as sub-100 fs fission time and equally long triplet lifetimes in both samples.

Journal Keywords: Excitons; Photoluminescence; Solar cells; X-ray diffraction; Solubility

Subject Areas: Physics, Materials


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