000130036 001__ 130036
000130036 005__ 20181203021340.0
000130036 0247_ $$2doi$$a10.1088/0957-4484/19/42/424003
000130036 02470 $$2ISI$$a000259483000004
000130036 037__ $$aARTICLE
000130036 245__ $$aCharge collection and pore filling in solid-state dye-sensitized solar cells
000130036 269__ $$a2008
000130036 260__ $$c2008
000130036 336__ $$aJournal Articles
000130036 520__ $$aThe solar to electrical power conversion efficiency for dye-sensitized solar cells (DSCs) incorporating a solid-state organic hole-transporter can be over 5%. However, this is for devices significantly thinner than the optical depth of the active composites and by comparison to the liquid electrolyte based DSCs, which exhibit efficiencies in excess of 10%, more than doubling of this efficiency is clearly attainable if all the steps in the photovoltaic process can be optimized. Two issues are currently being addressed by the field. The first aims at enhancing the electron diffusion length by either reducing the charge recombination or enhancing the charge transport rates. This should enable a larger fraction of photogenerated charges to be collected. The second, though less actively investigated, aims to improve the physical composite formation, which in this instance is the infiltration of mesoporous TiO2 with the organic hole-transporter 2,2',7,7'-tetrakis(N,N-di-p-methoxypheny-amine)-9,9'-spirobifluorene (spiro-MeOTAD). Here, we perform a broad experimental study to elucidate the limiting factors to the solar cell performance. We first investigate the charge transport and recombination in the solid-state dye-sensitized solar cell under realistic working conditions via small perturbation photovoltage and photocurrent decay measurements. From these measurements we deduce that the electron diffusion length near short-circuit is as long as 20 µm. However, at applied biases approaching open-circuit potential under realistic solar conditions, the diffusion length becomes comparable with the film thickness, ~2 µm, illustrating that real losses to open-circuit voltage, fill factor and hence efficiency are occurring due to ineffective charge collection. The long diffusion length near short-circuit, on the other hand, illustrates that another process, separate from ineffective charge collection, is rendering the solar cell less than ideal. We investigate the process of TiO2 mesopore infiltration with spiro-MeOTAD by examining the cross-sectional images of and performing photo-induced absorption spectroscopy on devices with a range of thickness, infiltrated with spiro-MeOTAD with a range of concentrations. We present our interpretation of the mechanism for material infiltration, and by improving the casting conditions demonstrate efficient charge collection through devices of over 7 µm in thickness. This investigation represents an improvement in our understanding of the limiting factors to the dye-sensitized solar cell. However, much work, focused on composite formation and improved kinetic competition, is required to realize the true potential of this concept.
000130036 700__ $$aSnaith, H. J.
000130036 700__ $$0240190$$g107384$$aHumphry-Baker, R.
000130036 700__ $$0240192$$g167609$$aChen, P.
000130036 700__ $$0240193$$g159958$$aCesar, I.
000130036 700__ $$0240194$$g106763$$aZakeeruddin, S.M.
000130036 700__ $$0240191$$g105292$$aGraetzel, M.
000130036 773__ $$j19$$tNanotechnology$$k42$$q424003
000130036 909C0 $$xU10101$$0252060$$pLPI
000130036 909CO $$pSB$$particle$$ooai:infoscience.tind.io:130036
000130036 937__ $$aLPI-ARTICLE-2008-066
000130036 973__ $$rREVIEWED$$sPUBLISHED$$aEPFL
000130036 980__ $$aARTICLE