At the upcoming glasstec 2014 exhibition in Düsseldorf in October, an entire segment will be dedicated to solar glazing to underline advances in technology that will turn building glass fronts into power plants.

The increasing energy consumption in urban areas demands that buildings become increasingly efficient and integrate more renewable energies. New, printable photovoltaic semiconductors could help to boost this trend by enabling solar films and modules to be produced, which transform windows or façades into electric power generators.

Perowskit is currently considered to be the best solar cells material in terms of efficiency levels and is also inexpensive. The best silicon cells available today achieve an efficiency level of over 20%, but are expensive to produce. Researchers at the University of California in Los Angeles (UCLA) recently achieved an efficiency level of 19.3 percent with a Perowskit cell. Compared to the first Perowskit cells five years ago, the efficiency level has thus increased six-fold.

Perowskit consists of carbon, nitrogen, hydrogen, lead, chlorine and iodine, which can be vapour-deposited onto glass as a wafer-thin layer or printed on film and foils. The UCLA researchers produced a Perowskit layer of just around one millimeter thickness by vaporising glass with organic molecules and lead crystals. Nevertheless, the cell generates almost as much electricity as a 180 micro-meter thick silicon cell.

As a result, the high-performance lightweights could conquer the markets which were previously, to a great extent, taboo for photovoltaics. Building integrated photovoltaics for example, in short BIPV continues to be just a niche market, because the manufacture and installation of multi-functional BIPV modules is costly and expensive. Of the 3,300 Megawatt solar power output, which went online in 2013 in Germany, it is estimated that only around 100 Megawatt was integrated in building shells. Perowskit cells could help to reduce costs.

Existing technologies for BIPV have previously not been efficient enough. Often modules made of thin-layer silicon are available, but they rarely reach an efficiency level of 10%. They are only suitable to a certain extent for building integration; they are sawn straight out of blocks because they are simply too thick and inflexible for more complex BIPV applications.

Nevertheless experts are hoping for an imminent breakthrough in building-integrated photovoltaics, because it has immense climate protection potential. Although major cities only account for one percent of the Earth’s total surface, they consume 75 percent of the primary energy used and cause 80 percent of greenhouse gas emissions.

Scientist Christina Sager from the Fraunhofer Institute for Building Physics (Institut für Bauphysik - IBP) in Stuttgart believes more efficient buildings and renewable energies, and solar technology, in particular, could be effectively integrated in houses. Where the modules cannot be fixed to rooftops, they could serve as power-generating windows or as a substitute for the concrete façade.

However, until the promising Perowskit cells can be used commercially, researchers still have to master several challenges. The service life is regarded as the greatest hurdle. Perowskit is sensitive and quickly degrades when it comes into contact with water. For that reason the cells must be designed in such a way, that even over a period of 20 years no moisture must be allowed to penetrate them. Leak-proof encapsulations, which were developed for organic light-emitting diodes are one possible solution.

There are other promising technologies currently ready for market introduction, which have been able to drive forward the BIPV market. Dresden company Heliatek has developed an organic photovoltaic film, which can be produced both in transparent as well as tinted form. In non-transparent form it reaches an efficiency level of twelve percent, while the translucent variation has a reduced efficiency level down to around seven percent. Compared to conventional silicon modules this is low, but in the area of organic photovoltaics it sets a new record. In addition, the flexible films can be embedded in curved formats such as glass car roofs or irregularly formed façades.

Developments based on the concept of flexible and transparent cells in organic material include printed polymer cells by Bavarian company Belectric as well as Crystalsol from Austria. Polymers are chemical combinations of long molecule chains, which can be enriched in a solution and then printed. Heliatek in contrast, uses oligomers as light collectors involving shorter molecule chains. In addition, it does not print, but vaporises them in a vacuum onto a carrier film. The company has just set up the first window façade in Dresden using solar films from this production line. The next step planned by the company is commercial production with an annual capacity of 100 Megawatt.

Timo Feuerbach from the Glass Technology Forum (Forum Glastechnik) within the German Engineering Federation (VDMA) comments that BIPV has not yet made an impact; however, it is definitely essential for the glass and photovoltaics industry to come closer together. In this connection, Heliatek and Brussels-based flat glass manufacturer AGC Glass Europe last year concluded a development agreement for the integration of solar films in construction glass. AGC technology boss Marc Van Den Neste says that the glass/solar façade solution created by the two companies is opening up completely new possibilities for architects and designers to combine creativity and energy efficiency with each other.

At glasstec 2014 in Düsseldorf, from 21 to 24 October 2014, the world's largest and most international trade fair for the glass sector, companies will have the opportunity to pave the way for further co-operations.

Experts from the solar power and glass industry will come together from 20 to 21 October 2014 at the ‘Solar meets Glass’ conference to discuss advances in the production of solar glazing and modules as well as the material and costs. The ‘glass technology live’ special show, which has been organised by the Institute of Building Technology, Construction and Design (Institut für Baukonstruktion) at Stuttgart University, will focus on the interface between solar technology and glass. The latest developments in the façade and energy sector will also be presented including innovations in photovoltaics and solar thermal energy.