Impact of unbalanced charge transport on the efficiency of normal and inverted solar cells

In a normal solar cell, most charge carriers are generated close to the anode, such that electrons have to travel a longer distance as compared to the holes. In an inverted solar cell, holes have to travel a longer distance. We use a combined optical and electronic model to simulate the effect of unbalanced transport on the efficiency of normal and inverted single and tandem solar cells. When the electrons are ten times more mobile than the holes, the efficiency for a single cell with a thickness of 250 nm drops from 7.5% to 4.5% when changing from a normal to an inverted structure. For opposite mobility ratio, the inverted structure clearly outperforms the normal structure.