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Characterizing the Role of Iodine Doping in Improving Photovoltaic Performance of Dye‐Sensitized Hierarchically Structured ZnO Solar Cells
Author(s) -
Zhao JiaXing,
Zheng YanZhen,
Lu XinHong,
Chen JianFeng,
Tao Xia,
Zhou Weilie
Publication year - 2013
Publication title -
chemphyschem
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.016
H-Index - 140
eISSN - 1439-7641
pISSN - 1439-4235
DOI - 10.1002/cphc.201300066
Subject(s) - doping , materials science , dye sensitized solar cell , dielectric spectroscopy , iodine , kelvin probe force microscope , solar cell , triiodide , optoelectronics , open circuit voltage , nanotechnology , analytical chemistry (journal) , chemistry , electrochemistry , electrode , atomic force microscopy , voltage , physics , quantum mechanics , chromatography , electrolyte , metallurgy
We report two novel types of hierarchically structured iodine‐doped ZnO (IZnO)‐based dye‐sensitized solar cells (DSCs) using indoline D205 and the ruthenium complex N719 as sensitizers. It was found that iodine doping boosts the efficiencies of D205 IZnO and N719 IZnO DSCs with an enhancement of 20.3 and 17.9 %, respectively, compared to the undoped versions. Transient absorption spectra demonstrated that iodine doping impels an increase in the decay time of IZnO, favoring enhanced exciton life. Mott–Schottky analysis results indicated a negative shift of the flat‐band potential ( V fb ) of ZnO, caused by iodine doping, and this shift correlated with the enhancement of the open circuit voltage ( V oc ). To reveal the effect of iodine doping on the effective separation of e − ‐h + pairs which is responsible for cell efficiency, direct visualization of light‐induced changes in the surface potential between IZnO particles and dye molecules were traced by Kelvin probe force microscopy. We found that potential changes of iodine‐doped ZnO films by irradiation were above one hundred millivolts and thus significantly greater. In order to correlate enhanced cell performance with iodine doping, electrochemical impedance spectroscopy, incident‐photon‐current efficiency, and cyclic voltammetry investigations on IZnO cells were carried out. The results revealed several favorable features of IZnO cells, that is, longer electron lifetime, lower charge‐transfer resistance, stronger peak current, and extended visible light harvest, all of which serve to promote cell performance.