Organic solar cells face efficiency challenge due to slow current flow, researchers show

Researchers from the Chair of Optics and Photonics of Condensed Matter led by Prof. Dr. Carsten Deibel on the Chemnitz College of Expertise and different associate establishments are at present engaged on photo voltaic cells constructed from novel natural semiconductors that may be produced utilizing established printing processes. The scientists are collaborating interdisciplinarily to basically perceive these photovoltaic cells with a purpose to additional enhance them.

“Organic solar cells can be produced very easily and cheaply using printing processes,” says Deibel. In distinction to established solar modules fabricated from crystalline siliconnevertheless, the present circulate in organic solar cells may be very gradual.

“Due to the production of the solar cells from a kind of ink, the organic, light-absorbing layers are very disordered. Therefore, the current flow is very slow,” explains Deibel. A consequence of the gradual transport of light-generated electrons and holes is the so-called transport resistance, which reduces the fill issue of the photo voltaic cells and thus the ability.

Deeper understanding: Transport resistance limits the efficiency of natural photo voltaic cells

To raised perceive the efficiency traits of natural photo voltaic cells, Deibel and his scientific assistant Maria Saladina have produced and completely investigated various kinds of natural photo voltaic cells and uncovered the damaging affect of transport resistance. The present-voltage traits underneath illumination, which consequence from the interaction of cost era by gentle, recombination of electrons and holes, and cost transport, have been measured. They comprise info on the ability effectivity of the photo voltaic cells.

These measurements have been in contrast with the so-called suns-Voc methodology, which permits the development of another current-voltage curve that’s not restricted by cost transport losses reminiscent of transport resistance. “Transport resistance is a result of the slow charge carriers in the disordered solar cells processed from organic ink. Thus, the charge carriers get in their own way and lead to a loss of fill factor and thus power,” says Saladina.

The research results have been printed in Experiences on Progress in Physics. Though the optimization of natural photo voltaic cells should be re-evaluated as a consequence of these new outcomes, there isn’t a elementary impediment to producing extremely environment friendly, printed natural photo voltaic cells.

In a perspective article printed within the journal Superior Vitality Supplieswritten by Chen Wang, Deibel, and Saladina along with co-authors from numerous German universities, the bodily origin of transport resistance and its significance for photo voltaic cells is defined intimately.

“In recent years, charge transport has been continuously improved without the research community knowing the exact relationship between fill factor losses and transport resistance,” says Deibel.

Saladina provides, “In addition to recombination, transport resistance is also determined by the shape of the density of states of organic solar cells. This shows that we are, step-by-step, understanding the physical foundations of these photovoltaic devices better and better.”

These outcomes have been achieved throughout the framework of the DFG Analysis Unit POPULAR, which continues to work on understanding and bettering printed natural photo voltaic cells.