07-Nov-2013 - Empa (Eidgenössische Materialprüfungs- und Forschungsanstalt)

Understanding what makes a thin film solar cell efficient

For many years scientists and engineers have been trying to provide low-cost solar energy by developing a cheap solar cell that is both highly efficient and at the same time simple to build, enabling it to be mass produced. Now, the team led by Empa researcher Ayodhya N. Tiwari has made a major leap forward: the researchers are presenting a new manufacturing technique for CIGS solar cells, in which tiny quantities of sodium and potassium are incorporated into the CIGS layer. The special treatment alters the chemical composition of the complex sandwich structure – thereby altering its electronic properties, as confirmed by various methods including detailed electron microscope investigations.

With this technique, the Empa team has again been able to significantly increase the energy conversion efficiency from sunlight into electricity using CIGS thin film solar cells on flexible plastic foils – to a new record level of 20.4%, representing a marked improvement over the previous record of 18.7% established by the same team in May 2011. This finally enables CIGS cells to compete with the best polycrystalline silicon cells. Until recently, the Empa CIGS cells were the most efficient in the world; at the end of October, though, a German research team at the Zentrum für Sonnenenergie- und Wasserstoff-Forschung (ZSW) in Stuttgart presented CIGS cells with an efficiency of 20.8%, although they use far higher processing temperatures and (rigid) glass as the substrate. The slightly improved record shows that CIGS thin film technologies are a "hot" topic.

Facts, background information, dossiers
More about Empa
  • News

    When damaged ropes change color

    High-performance fibres that have been exposed to high temperatures usually lose their mechanical properties undetected and, in the worst case, can tear precisely when lives depend on them. For example, safety ropes used by fire brigades or suspension ropes for heavy loads on construction s ... more

    Turning streetwear into solar power plants

    Empa researchers succeeded in developing a material that works like a luminescent solar concentrator and can even be applied to textiles. This opens up numerous possibilities for producing energy directly where it is needed, i.e. in the use of everyday electronics. Our hunger for energy is ... more

    The Transistor out of the Printer

    Empa researchers are working on electronics that come out of printers. This makes it possible to produce the circuits on all sorts of substrates, such as paper or plastic film – but there are still some hurdles to overcome. Imagine being able to easily print electronics on any surface. Toda ... more

  • Videos

    A water-based, rechargeable battery

    First step to produce a cheap aquous electrolyte for powerful rechargeable batteries: Seven grams of sodium FSI (precise name: sodium bis(fluorosulfonyl)imide) and one gram of water produce a clear saline solution with an electrochemical stability of up to 2.6 volts – twice as much as other ... more

More about ZSW
  • News

    Sustainable Chemical Production with Electricity

    By 2050, the chemical industry should operate in a climate neutral fashion, which means phasing-out fossil oil, gas and coal. Therefore alternative carbon sources and renewable energy have to be utilized in order to replace fossil reserves. A new Stuttgart Research Initiative will elaborate ... more

  • Companies

    Zentrum für Sonnenenergie- und Wasserstoff-Forschung Baden-Württemberg (ZSW)

    The ZSW is one of the most renowned German institutes of applied research in the fields of photovoltaics, energy systems analysis, renewable fuels, battery technology, and fuel cells. More than 200 scientists, engineers, and technicians are currently employed at its three facilities in Stut ... more