Dyesol : October Q&A 2016

Our Managing Director, Richard Caldwell, answers your questions sent during the month of October 2016.

At a conference it just has been reported that tandem Perowskit Solar cells might have an efficiency of over 30%. Regarding to an article of SolarServer, the EPFL is also involved in this research. Is Dyesol also working on tandem Solar Cells (Perowskit - Silicium)?

Dyesol has considered carefully the various technology opportunities which best match perovskite solar cells, and has decided not to work on perovskite-silicon tandem devices at this stage. Reasoning for this choice includes:

• In order to achieve the quoted ~30% perovskite-silicon tandem efficiencies, both the silicon and perovskite solar cells would need to be >20% independently in their own right, due to parasitic losses were either both photoactive absorbers capture sunlight, or the required interfacial layers between the two stacked cells absorbed light with no charge generation.

• To ensure appropriate lifetime, both silicon and perovskite would need to degrade at similarly slow rates. Further, perovskite, being the 'top' device where light enters the tandem, would need to also maintain light transmissive characteristics outside its own absorption window without degradation in these characteristics, which have no direct bearing on the perovskite device performance, but which critically impact the overall tandem power output.

• The anticipated $/Wp decrease for a theoretically optimum perovskite-silicon tandem device over a silicon-only device is around 15%. This is a combination of the small increase in cost due to adding the perovskite, which is exceeded by the modest increase in power output. At first glance this would appear to make economic sense. However, the main cost in the silicon systems is the silicon solar cells (~60%).

• As a requirement for a perovskite-silicon tandem is long-life high-efficiency perovskite, it makes more sense to produce a high efficiency perovskite-only device, which will have costs <50% of a silicon module as well as comparable performance, and thus at least 50% lower $/Wp. This approach also eliminates the need for dealing with technically complex integration issues in materials and process selection for creating a perovskite-silicon tandem, such as wavelength-specific transparency and degradation, as well as silicon substrate-compatibility restrictions and interfacial material requirements, which are much more limiting than the options for creating a perovskite-only device.

Dyesol does consider, however, that a future efficiency expansion opportunity in perovskite devices is a perovskite-perovskite tandem configuration. Once an initial generation single-junction perovskite system is commercially viable, a relatively logical advance is to produce a tandem using two different perovskites, which provides most of the advantages of a tandem such as high efficiency, without the cost of an underlying silicon cell. Naturally, Dyesol of course keeps a close watch on perovskite-silicon tandem developments, including work carried out by our Partner EPFL, to remain best informed regarding the prospects and challenges presented by such opportunities.

Is Dyesol in any discussions with car manufactures?

No - historically, we have explored DSC opportunities with a large German manufacturer, but we see the most exciting opportunities for commercial exploitation in the field e.g. utility installations, and on buildings (BIPV). The most sensible and economic use of renewable energy is the overnight downloading of electricity generated from renewable sources from the home or similar. This will unlock the true value of electric vehicles and highlights the importance of battery technology and its close interdependence with solar PV.

How does Dyesol plan to finance the next steps until mass manufactory? How much money does Dyesol need?

The financing of commercial development is the subject of discussion with governments around the world. Governments have shown a strong interest to assist, subject to demonstrating that the technology is commercial-ready. This is one of the principal reasons that Dyesol has a rigorous commercialization schedule focused on Prototype, Pilot Line and Mass Manufacture. This is a staged risk mitigation process. If the technology can demonstrate that it is competitive, the finance will be available from multiple sources at the project level, including debt funding.