Theoretical Studies on the Effect of Sensitizing Dyes on yhe Performance of Ruthenium Dye-Sensitized Solar Cells DSSCs Based on Quantum Electronic Transition

In this work, the efficiency and characteristic of ruthenium sensitized based on TiO2 semiconductor in dye sensitized solar cells DSSCs are calculated and studied using electron transfer theory .The electron transfer raction occurred from the donor state in excited ruthenium dye N3 and N719 dyes to the acceptor state in the semiconductor TiO2 has been elucidated. The current density was calculated using the quantum charge transport theory, based on the donor-receiver model. In this model, the current density as results of electron transfer from the excited N3 and N719 dyes into the TiO2 is subjected to the effects of reorganization energy, the atomic density, and the charge concentration and coupling.The reorganization energy a N3/TiO2 and N719/TiO2  cells depends greatly on polarity of the acetonitrile solvent medium, the physic strength, al structure of N3 ,N719 and TiO2 materials the distance between the N3 and N719 dyes and TiO2.A high reorganization energy for N3/TiO2 decreases the probability of electron transfer and increase reocobination charge , while a low reorganization energy for N719/TiO2 increases the rate of electon transfer  and decreases the rate of reocobination charge. A discussion of the reorganization energy reveals that N3,N719 , TiO2  and acetonitrile solvent properties play a crucial role in modifying electron transfer between N3 and N719 dyes and TiO2 surfaces under different coupling strength, and room temperatures. The current density increases significantly with decreasing the reorganization energy and increasing coupling overcoming, as a result of the increased alignment energy level  of the materials  system.The high current density occurred mainly as a result of the strong bond between the N719 dye and TiO2 comparing with low at N3 with TiO2 , which led to increased wavefunction overlap at the interface, thus enhancing the electron transport of the N719/TiO2 device. Based on the results, the overall performance of the N719/TiO2 device can be improved by increased  charge transport and reach to 5.337% larger than 3.783% for N3/TiO2 , where reorganization energy affects controls, and  coupling controls the electron transport.