J-V characteristics of dark and illuminated classical and inverted organic solar cells based on the CuPc/C₆₀ heterojunction

A comparison of the performances of classical and inverted organic solar cells based on the junction copper phthalocyanine/fullerene (CuPc/C ₆₀) shows that the former devices give the best efficiency. The transport properties of charge carriers in the organic material and the interface properties have been investigated using a mathematical simulation taking into account the effect of bulk and interface properties. Good agreement between experimental and calculated values can be achieved using different parameter values following the type of solar cells. In classical solar cells, the current is space charge limited, while there is no barrier at the contact electrode/organic material. In the case of inverted solar cells it is necessary to introduce a barrier contact at these interfaces to achieve a good fit between experimental and theoretical values. Therefore, the lower efficiency of the inverted solar cells is due to the barrier contact at the interface and smaller electrode work function difference.