Electron-Selective ‍Lithium Contacts for Crystalline Silicon Solar Cells

Separating photogenerated charge carriers by carrier-selective heterostructure contacts rather than by doped homojunctions is a promising pathway to approach the theoretical power conversion efficiency (PCE) limit of crystalline silicon (c-Si) solar cells. An electron-selective, hole-blocking lithium contact for c-Si solar cells is presented by simple thermal evaporation of air-stable Li3N powder. It is found that this lithium contact introduces only a minimal Schottky-barrier height for electron transport at its interface with lightly doped n-type c-Si surfaces, resulting in a low contact resistivity of 12.8 mΩ cm2. By implementing a full-area electron-selective lithium contact, an n-type c-Si solar cell with a PCE of 19% is achieved, representing a 4% absolute PCE improvement over reference devices with an aluminum contact. The choices of electron-selective contact materials for photovoltaic devices, using simple, scalable fabrication methods are extended.