Tham khảo tài liệu 'solar cells dye sensitized devices part 14', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | 382 Solar Cells - Dye-Sensitized Devices were able to demonstrate an enhancement in both light harvesting and the injection yield when zinc and free base porphyrin dyes were combined on the same TiC 2 surface Griffith Mozer et al. 2011 . Other groups have also pursued similar studies focusing on extending the co-sensitization concept using energy relay systems. This approach involves dissolving the co-sensitizer in the electrolyte so that it no longer competes with the major sensitizer for binding sites on the semiconductor. Absorbed photon energy is transferred from the dissolved co-sensitizer to the chemically bound major sensitizer where it is then injected into the semiconductor. This approach achieved photocurrent enhancements of 30 compared to direct co-sensitization on the same semiconductor surface Hardin Hoke et al. 2009 . Electron injection into semiconducting oxides Electron injection from the photoexcited dye into the acceptor states of the semiconductor conduction band is perhaps the key mechanistic step in achieving efficient charge generation in DSSCs. According to the classical theory of electron transfer developed by Marcus the rate of electron transfer kET between discrete donor and acceptor levels under non-adiabatic conditions is given by Marcus 1964 Zn H2 f- A AG02r kET Y exp ft y 4riLkBT 4xlfcBT J 5 where H2 is the electronic coupling between donor and acceptor states AGo is the free energy driving force for electron transfer Ấ is the total reorganization energy T is the absolute temperature and h and ka the Planck and Boltzmann constants respectively. The electronic coupling H2 decreases exponentially with increasing distance d between the donor and the acceptor as H2 H02 exp fld 6 where p is related to the properties of the medium between donor and acceptor and Ho2 is the coupling at distance d 0. To achieve high efficiencies for injection in DSSCs electron injection must be at least an order of magnitude faster than the competing .
