Electron-Selective Strontium Oxide Contact for Crystalline Silicon Solar Cells with High Fill Factor

Extensive efforts have been made to develop wide-bandgap metal compound-based carrier-selective contacts to improve the performance of crystalline silicon (c-Si) solar cells, by mitigating the deleterious effects of metal-Si contact directly. Herein, thermally evaporated wide-bandgap strontium oxide (SrOx) is exploited as an electron-selective contact for c-Si solar cells. Benefiting from a lower work function (3.1 eV) of SrOx, a strong downward band-bending is achieved at the n-type c-Si/SrOx interface, enabling the electron-selective transport characteristic. Thin SrOx films simultaneously provide moderate surface passivation after annealing and enable a low contact resistivity on c-Si surfaces. By the implementation of a single-dielectric-layer SrOx-based rear contact, a champion power conversion efficiency of 20.0% is realized on the n-type c-Si solar cell featuring an intriguing fill factor of 82.8%. Moreover, electron-selective SrOx contact is demonstrated to show high thermal stability up to 500 degrees C. The SrOx layer formed by a facile thermal evaporation process presents a unique opportunity to develop highly efficient and low-cost c-Si solar cells.