HOPV12 - Blogs

Recommendations

Info

4 th Hybrid and Organic Photovoltaic Conference -Uppsala 2012 119 C18 - Fast Transporting ZnO-TiO2 Coaxial Photoanodes for Dye-Sensitized Solar Cells Based on ALD-Modified SiO2 Aerogel Frameworks Vennesa Williams a , Nak Cheon Jeong a , Chaiya Prasittichai a , Michael Pellin a , Joseph Hupp a a, Depatment of Chemistry and Argon-Northwestern Solar Energy Research Center (ANSER), Northwestern University, 2145 N Sheridan Rd, Evanston, 60208, USA b, Materials Science Division, Argonne National Laboratory, 9700 S. Cass Avenue, Argonne, IL 60439, USA c, Chemical Science and Engineering Division, Argonne National Laboratory, 9700 S. Cass Avenue, Argonne, IL 60439, USA A doubly co-axial photoanode architecture based on templated SiO2 aerogels was fabricated on transparent conducting oxides for use in dye-sensitized solar cells (DSSCs). These templates were coated with ZnO via atomic layer deposition (ALD) to yield an electronically interconnected, low density, high surface area, semiconductor framework. Addition of a thin conformal layer of a second metal oxide (alumina, zirconia, or titania) via ALD was found to suppress the dissolution of ZnO that otherwise occurs when it is soaked in alcohol solutions containing acidic dyes used for sensitization or in acetonitrile solutions containing a pyridine derivative and the iodide/tri-iodide (I - /I - 3) redox shuttle. Electron transport in SiO2-ZnO-TiO2 photoelectrodes was found to be nearly two orders of magnitude faster than in SiO2-TiO2 structures, implying that the interior ZnO sheath serves as the primary electron conduit. In contrast, rates of electron interception by the oxidized form of the redox shuttle were observed to decrease when a TiO2 shell was added to SiO2-ZnO, with the decreases becoming more significant as the thickness of the titania shell increases. Figure 1 A doubly co-axial photoanode architecture (ZnO-TiO2) based on templated SiO2 aerogels for use in DSSCs to effectively improve photocurrents, photovoltages and electron lifetimes These effects lead to improvements in efficiency for DSSCs that utilize I - /I - 3, but much larger improvements for DSSCs utilizing ferrocene/ferrocenium, a notoriously fast redox shuttle. For the former, overall energy conversion efficiencies maximize at 5.2%. From a variety of experiments, the primary factor limiting aerogel-based DSSC performance is light loss due to scattering. Nevertheless, variants of the doubly coaxial structure may prove useful in devising DSSCs that can achieve excellent energy conversion efficiencies even with fast redox shuttles. © SEFIN 2012
4 th Hybrid and Organic Photovoltaic Conference -Uppsala 2012 120 C19 - The effect of the spatial and energetic carrier distribution on the charge carrier lifetime in bulk heterojunction solar cells Thomas Kirchartz, Jenny Nelson Imperial College London, Department of Physics, South Kensington Campus, London, 0, GB Charge extraction and transient photovoltage measurements have been extensively used to study non-geminate recombination in polymer:fullerene solar cells. 1-3 In particular, it has been shown that a combination of both enables a successful reconstruction and explanation of the recombination current of different polythiophene:fullerene devices. 4 However, what is missing so far is a detailed theoretical study on the relation between the spatial and energetic distribution of carriers on the results obtained from charge extraction and transient photovoltage measurements. We show that the voltage and carrier concentration dependence of the lifetime can be derived from the diode ideality factor and the voltage dependence of the carrier concentration. To study the effect of the density of states as a function of energy on the results, we employ a drift-diffusion solver using a Shockley-Read-Hall model for recombination via continuous distributions of localized states. In case of sufficiently thick (> 150nm) and undoped solar cells, the ideality factor and the voltage dependence of the carrier concentration reflect the shape of the density of states with deeper states leading to higher ideality factors. 5,6 When reducing the thickness, the ideality factor will still reflect the dominant recombination mechanism, while the voltage dependence of the carrier concentration will now be affected by the spatial distribution and the energetic distribution of charge carriers. This leads to a slow increase of carrier concentration with voltage and therefore to very high apparent reaction orders as seen in experiment. Unintentional doping of the active layer can have a similar effect depending on the device thickness. For low thicknesses and low doping concentrations, the space-charge region would be bigger than the active layer thickness and the effect of the doping is negligible. For higher active layer thicknesses, doping can alter the spatial distribution of electron and hole concentrations such that again a rather slow increase of carrier concentrations with voltage is observed, which then causes high apparent reaction orders that do not reflect the physical recombination mechanism anymore. This study will be applicable and relevant to bulk heterojunction solar cells made from organic or inorganic materials with thicknesses in the range of a few hundred nanometers or less. References [1] Shuttle, C. G.; O'Regan, B.; Ballantyne, A. M.; Nelson, J.; Bradley, D. D. C.; de Mello, J.; Durrant, J. R. "Experimental determination of the rate law for charge carrier decay in a polythiophene: Fullerene solar cell". Appl. Phys. Lett. 92, 093311 (2008). [2] Maurano, A.; Hamilton, R.; Shuttle, C. G.; Ballantyne, A. M.; Nelson, J.; O'Regan, B.; Zhang, W. M.; McCulloch, I.; Azimi, H.; Morana, M.; Brabec, C. J.; Durrant, J. R. "Recombination Dynamics as a Key Determinant of Open Circuit Voltage in Organic Bulk Heterojunction Solar Cells: A Comparison of Four Different Donor Polymers." Adv Mater 22, 4987-4992 (2010) [3] Credgington, D.; Hamilton, R.; Atienzar, P.; Nelson, J.; Durrant, J.R. "Non-Geminate Recombination as the Primary Determinant of Open-Circuit Voltage in Polythiophene:Fullerene Blend Solar Cells: an Analysis of the Influence of Device Processing Conditions". Adv Funct Mater 21, 2744 - 2753 (2011). [4] Shuttle, C. G.; Hamilton, R.; O'Regan, B.; Nelson, J.; Durrant, J. R. "Charge-density-based analysis of the current– voltage response of polythiophene/fullerene photovoltaic devices". P Natl Acad Sci USA 107, 16448 (2010). [5] van Berkel, C.; Powell, M. J. Franklin, A. R., French, I. D., "Quality factor in a‐Si:H nip and pin diodes". J. Appl. Phys. 73, 5264-5268 (1993) (6) Kirchartz, T.; Pieters, B. E.; Kirkpatrick, J.; Rau, U.; Nelson, J. "Recombination via tail states in polythiophene: fullerene solar cells." Phys. Rev. B 83, 115209 (2011). © SEFIN 2012
Page 3 and 4:
4 th Hybrid and Organic Photovoltai
Page 5 and 6:
The 4th International Conference on
Page 7 and 8:
Page 9 and 10:
Page 11 and 12:
Page 13 and 14:
Page 15 and 16:
Page 17 and 18:
Page 19 and 20:
Page 21 and 22:
Page 23 and 24:
Page 25 and 26:
Page 27 and 28:
Page 29 and 30:
Page 31 and 32:
Page 33 and 34:
Page 35 and 36:
Page 37 and 38:
Page 39 and 40:
Page 41 and 42:
Page 43 and 44:
Page 45 and 46:
Page 47 and 48:
Page 49 and 50:
Page 51 and 52:
Page 53 and 54:
Page 55 and 56:
Page 57 and 58:
Page 59 and 60:
Page 61 and 62:
Page 63 and 64:
Page 65 and 66:
Page 67 and 68:
Page 69 and 70: 4 th Hybrid and Organic Photovoltai
Page 119: 4 th Hybrid and Organic Photovoltai
Page 171 and 172:
Page 173 and 174:
Page 175 and 176:
Page 177 and 178:
Page 179 and 180:
Page 181 and 182:
Page 183 and 184:
Page 185 and 186:
Page 187 and 188:
Page 189 and 190:
Page 191 and 192:
Page 193 and 194:
Page 195 and 196:
Page 197 and 198:
Page 199 and 200:
Page 201 and 202:
Page 203 and 204:
Page 205 and 206:
Page 207 and 208:
Page 209 and 210:
Page 211 and 212:
Page 213 and 214:
Page 215 and 216:
Page 217 and 218:
Page 219 and 220:
Page 221 and 222:
Page 223 and 224:
Page 225 and 226:
Page 227 and 228:
Page 229 and 230:
Page 231 and 232:
Page 233 and 234:
Page 235 and 236:
Page 237 and 238:
Page 239 and 240:
Page 241 and 242:
Page 243 and 244:
Page 245 and 246:
Page 247 and 248:
Page 249 and 250:
Page 251 and 252:
Page 253 and 254:
Page 255 and 256:
Page 257 and 258:
Page 259 and 260:
Page 261 and 262:
Page 263 and 264:
Page 265 and 266:
Page 267 and 268:
Page 269 and 270:
Page 271 and 272:
Page 273 and 274:
Page 275 and 276:
Page 277 and 278:
Page 279 and 280:
Page 281 and 282:
Page 283 and 284:
Page 285 and 286:
Page 287 and 288:
Page 289 and 290:
Page 291 and 292:
Page 293 and 294:
Page 295 and 296:
Page 297 and 298:
Page 299 and 300:
Page 301 and 302:
Page 303 and 304:
Page 305 and 306:
Page 307 and 308:
Page 309 and 310:
Page 311 and 312:
Page 313 and 314:
Page 315 and 316:
show all

HOPV12 - Blogs

Create successful ePaper yourself

Delete template?

Save as template?