Japanese researchers demonstrated a new concept of "heat recovery" solar cells, which they claim may exceed the theoretical limit of battery efficiency. However, they said that they have not yet found a suitable material for the energy filter layer. The battery is equipped with a 100-micron thick silicon absorber. Two electrodes and an energy-carrying filter layer are placed between the absorber and the electrodes.

     According to the analysis of the Micro Lithium Battery Group, unlike traditional solar cells, this type of battery has a positive temperature dependence, which means that the efficiency of the absorber increases as the temperature rises. In addition, Kamide said: "The key and most challenging technology to achieve this goal is to find the right energy filter layer material to avoid any other problems that may occur when installed in the (heat recovery) HERC structure."

     When asked about the cost of this battery, Kamide said that since the candidate materials have not yet been determined, cost estimates are not yet available. He affirmed: "Of course, low-cost materials should be better."