En Mulig Fotokemisk Reaktion I Grätzel-solcellen

Esben Mortensen & Thomas Balle

Studenteropgave: Semesterprojekt

Abstrakt

The project is based on a photochemical reaction in a Grätzel solar cell. Former experiments has proven that the effect from the solar cell drops if heated to 85° C in the dark. This occurs mainly becaurse of an thermal substitution reaction between the dye [RuL2(NSC)2] named N719 and the solar cell additiv 1-methylbenzoinidazole (MBI). This forms the substituted compound [RuL2(MBI)(NCS)]+. By a consecutive illumination at 45° C a regeneration of the efficiency occurs. This is caused by a yet unknown photochemical reaction. Our hypothesis is that [RuL2(MBI)(NCS)]+ will react by a photochemically reaction with the solar cell’s content of iodide by illumination. By doing this createing a new dye with the similar efficiency as N719: [RuL2(MBI)(NCS)+]*+2 I- → [RuL2(MBI)(I)]+ + (NCS)- + I- → [RuL2(I)(I)] + (NCS)- + (MBI) The hypothesis is tested experimental by making a quantitative analysis of the reaction between the dye and iodide under illumination from a LED-lamp with a known wavelength. The result indicates that the dye reacts in two different ways before making a di-iodo complex. 2 [RuL2(MBI)(NCS)]+* + 4I- → [RuL2(MBI)(I)]+ + [RuL2(NCS)(I)] + (NCS)- +(MBI) +2I- → [RuL2(MBI)(I)+]* + [RuL2(NCS)(I)]* +2I- +(NCS)- +(MBI) → 2[RuL2(I)(I)] +2(NCS)- +2(MBI) The quantum yield from the reaction to the intermediates is estimatet to be: 2,6 * 10-5 mol(due)/mol(photon) with the reaction constant kp = 5,2 * 10-3 s-1. The half-life time of the reaction by illumination of 0,8 sun (800w/m2) is estimated to be 12,3 hours. The quantum yield is compared with a similar realistic solar cell experiment. Here the reaction progressed is 10 * 13 times as slow. Our hypothesis can now be dismissed becaurse the half-life of the reaction would take and thus not be the cause for the regenerated effect in a Grätzel solar cell.

UddannelserBasis - Naturvidenskabelig Bacheloruddannelse, (Bachelor uddannelse) Basis
SprogDansk
Udgivelsesdato7 jun. 2010
VejledereTorben Lund & Phuong Tuyet Nguyen

Emneord

  • Grätzel
  • n719
  • kvanteudbytte
  • MS
  • Esben Mortensen
  • reaktion
  • UV/VIS
  • substitutionsreaktion
  • fotokemisk
  • sommeling
  • farvestofsensibiliserede solcelle
  • solcelle
  • HPLC