Molecular Modifications of Active and Anode Buffer Layers of Bulk Heterojunction Solar Cell

In this work, new photoactive materials were tested in the active and anode buffer layers of the inverted ITO|ZnO|donor:PC60/70BM|Buffer|Au/Ag organic bulk heterojunction (BHJ) solar cell. The molecular properties of the materials synthesized for this work were designed in order to improve the efficiency of the inverted solar cell structure. In addition to testing the materials in the cells, their effect on the cell function was investigated. The work aimed to understand the effects of the studied buffer and active layer materials in the cell function and photovoltaic performance. Organometallic n-type tris-(8-hydroxyquinoline)aluminum (Alq3) derivatives, p-type aryl end-capped quaterthiophenes, and a combined p- and n-type Alq3 end-capped hexathiophene were tested as hole transporting anode buffer layer materials. As the various different materials provided a diverse buffer material selection, the properties of the materials for improved cell function were investigated by spectroscopic, electrochemical, computational and thermoanalytical methods. The studied Alq3 derivatives have electron donating amino substituents, either piperidine, pyrrolidine or morpholine rings, on the 5-position of the 8-hydroxyquinoline ligands, which ease the oxidation of the complexes and elevate the highest occupied molecular orbital (HOMO) energy levels. The higher HOMO levels of the derivatives, compared to that of Alq3, reduce the hol