About the transparent electrode of the organic photovoltaic cells

Abstract

Abstract. Electrodes and the nature of their contact with organic materials play a crucial role in the realization of efficient optoelectronic components. Whether the injection (organic light emittin g diodesOLEDs) or collection (organic photovoltaic cells -OPV cells) of carriers, contacts must be as efficient as possible. To do this, it is customary to refer to electrode surface treatment and / or using a buffer layer all things to optimize the contac t. Efficiency of organic photovoltaic cells based on organic electron donor/organic electron acceptor junctions can be strongly improved when the transparent conductive anode is coated with a buffer layer (ABL). We show that an ultra-thin gold (0.5 nm) or a thin molybdenum oxide (3-5 nm) can be used as efficient ABL. However, the effects of these ABL depend on the highest occupied molecular orbital (HOMO) of different electron donors of the OPV cells. The results indicate that, in the case of metal ABL, a good matching between the work function of the anode and the highest occupied molecular orbital of the donor material is the major factor limiting the hole transfer efficiency. Indeed, gold is efficient as ABL only when the HOMO of the organic donor is clos e to its work function Au . MoO 3 has a wider field of application as ABL than gold , The role of the oxide is not so clearly understand than that of Au , different models proposed to interpret the experimental results are discussed.

Fabrication Parameter Optimization for a Multilayer Photovoltaic Cell Based on the Heterojunction: Zinc(II)-Meso-Tetrakis(4-Bromophenyl) Porphyrins/Fullerenes

“…The thickness of such metal oxide is important. A too thin ABL leads to inhomogeneous properties at the interface anode/ED by incomplete surface coating [19], while a too thick layer increases the serial resistance (Rs) and therefore reduces Jsc and FF. We have already shown that, in the experimental conditions used in this work, the optimum thickness of the MoO 3 ABL is 3 nm [20].…”

“…For BrPhPZn layers thick of 50 nm it is observed that the Jsc and Voc values are low, and they increase gradually as the film thickness diminishes. This response could be related to the low conductivity and hole mobility of the compound [19].…”