Research
Stability of Perovskite Solar Cells
Although the efficency of perovskite solar cells have exceeded 25% in recent years and can thus rival much more established techonlogies like crystallin silicon photovoltaics, the poor long-term stability of perovskite solar cells (PSCs) is still an ongoing challenge for successful commercialization.
Organic-inorganic perovskites are susceptible to many different intrinsic and extrinsic degradation pathways, currently hindering them to reach the 20+ years of lifetime required in the photovoltaic industry. Common degradation pathways include ionic migration, phase seggregation, thermal instability as well as weakness to oxygen and moisture.
Our group searches for ways to alleviate these detrimental effects, e.g. by compositional engeneering, grain boundary or interface passivation, or deploying new chage transport materials, trying to increase the lifetime of the whole device.
Lead-free Perovskite Solar Cells
Another focus of our research lies in the development of new lead-free PSCs. Lead which is used in most devices with high power conversion efficiency (PCE), is toxic and the used lead containig compounds are relatively easy soluble. Therefore an alternative is needed for sustainable energy production.
The most promising alternative to lead is its fellow group element tin, which is also widely studied in our group. There are still some challenges that have to be resolved before commercialization. One of the major challenges is the easy oxidation of active Sn(II) to inactive Sn(IV). Because of that additives like Tin(II)fluoride are needed to prevent oxidation.
A second challenge is the control of the film formation due to the faster crystallization of tin perovskites compared to their lead-based counterparts. This can lead to pinholes in the film which decrease the stability and efficiency of the device. Therefore more research is needed to make tin an efficient substitute to lead-based perovskites in the future.