Charge Transport and Photocurrent Generation Characteristics in Dye Solar Cells Containing Thermally Degraded N719 Dye Molecules

Anders Rand Andersen, Janne Halme, Torben Lund, Muhammad Imran Asghar, Nguyen Tuyet Phuong, Kati Miettunen, Erno Kemppainen, Ole Albrektsen

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By deliberately introducing the thermally de-graded form of the dye solar cell sensitizer N719 in dye-ensitized solar cells (DSCs) using synthetically prepared
N719-TBP ([Ru(L-H)2(NCS)(4-tert-butylpyridine)]- +N-(Bu)4), we have investigated the devastating influence of this ligand substitution product (N719-TBP) on the performance parameters of the cells. Two types of dyed solar cells, based on either N719 or N719-TBP, have been characterized employing standard current-voltage (I-V) performance test, UV-vis optical spectroscopy, incident photon to current efficiency (IPCE), and electrochemical impedance spectroscopy (EIS) methods. The performance tests show a drastic efficiency reduction of ∼50% in the N719-TBP containing cells as compared to N719-dyed cells. The lower performance of N719-TBP was caused by lower overall light harvesting efficiency due to ca. 30 nm blue shift in the absorption spectrum of the dye, ca. 50% shorter electron diffusion length due to lower electron recombination resistance, and ca. 14% lower charge separation efficiency, which most likely can be ascribed to decreased dye regeneration efficiency caused by the replacement of one NCS ligand with TBP in the substitution product. The observations made in this study of DSC cells dyed with the substitution product, representing a worst case scenario of cells with 100% degraded dye, are in agreement with the characteristics of N719-dyed solar cells degraded at 85 C, where the effect of ligand substitution is somewhat less pronounced.
TidsskriftJournal of Physical Chemistry Part C: Nanomaterials and Interfaces
Udgave nummer31
Sider (fra-til)15598-15606
Antal sider9
StatusUdgivet - 2011


  • Dye-sensitized solar cells

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