LIMA · Improve Photovoltaic efficiency by applying novel effects at the limits of light to matter interaction

The LIMA project exploits cutting edge photonic technologies to enhance silicon solar cell efficiencies with new concepts in nanostructured materials. It proposes nano-structured surface layers designed to increase light absorption in the solar cell while decreasing surface and interface recombination loss. Integration in a back contact design further reduces these interface losses and avoids shading.The project improves light-matter interaction by the use a surface plasmonic nanoparticle layer. This reduces reflection and efficiently couples incident radiation into the solar cell where it is trapped by internal reflection.Surface and interface recombination are minimised by using silicon quantum dot superlattices in a passivating matrix. The distance between quantum dots ensures wave-function overlap and good conductivity. An effective field at the superlattice - crystalline silicon interface ensures that the cell is insensitive to the recombination velocity at this heterojunction, and further increases the collection probability in the quantum dot layer.The dots allow a fundamental efficiency enhancement due to experimentally confirmed multiple exciton generation. This mechanism increases photocurrent and can in theory raise the theoretical single junction efficiency limit from 33% to 44%.These surface plasmonic and quantum dot layers are integrated in a high efficiency crystalline silicon back contact cell. This is designed such that the space charge region is separated from the superlattice – crystalline silicon heterojunction minimising non radiative space-charge recombination. The back contacts and dielectric electrical insulator are designed to maximise back surface reflection and enhance the light trapping of incident radiation without shading losses.The project combines expertise between academic and industrial partners. The goal is a high efficiency cell using novel concepts to enhance proven cell designs.