Improving hybrid solar cells by controlled energy level alignment at donor-acceptor interfaces (R-4053)

Organic/inorganic (hybrid) solar cells pose a very eligible alternative for classical silicon based photovoltaics, both with respect to ease of production and cost. The most fundamental difference between these newer device types and silicon-based ones is that upon absorption of light, bound electron-hole pairs (or excitons) are created rather than free charge carriers. Hence, in order to extract charges from such a solar cell, the excitons have to split at the interface between the electron-donating and -accepting compound. Energy level alignment between this donor and acceptor is a pivotal element for high efficiency operation of the photovoltaic cell. Despite that several models have been proposed to explain this alignment in organic and hybrid devices, a conclusive picture of the underlying physics did not emerge. However, fundamental insight in the occurring interfacial effects is of paramount importance to outline universal design rules towards more efficient solar cells. Therefore, this project strives to study the energetics at metal-oxide/polymer interfaces during the preparing of appropriate hybrid solar cells, and to correlate the obtained results with photovoltaic parameters derived from the same devices. Energy levels at both sides of the donor-acceptor interface are manipulated and controlled in a systematic way by introducing additional molecular interlayers with varying dipolar moments. This will enable us to identify the key parameters determining the efficiency in such devices and, thus, help to push their performance to significantly higher values.

Keywords:photovoltaic solar cells

Disciplines:Materials engineering