Hole-selective molybdenum oxide as a full-area rear contact to crystalline p-type Si solar cells

Abstract

We examine thermally evaporated MoOx films as a full-area rear contact to crystalline p-type Si solar cells for efficient hole-selective contacts. Prior to front- and rear-metallization, the implied open-circuit voltage (iVoc) is evaluated to be 646 mV with implied fill factor (iFF) of 82.5% for the tunnel SiOx/MoOx rear contacted cell structure with the passivated emitter on the textured surface, showing it is possible to achieve an implied 1-sun efficiency of 20.8%. Numerical simulation reveals that the electron affinity (χ) of the MoOx material strongly influences the performance of the MoOx contacted p-Si cell. Simulated band diagrams show that the values in χ of the MoOx layer must be sufficiently high in order to lower junction recombination, indicating that the highest efficiency of 21.1% is achievable for a high χ of 5.6 eV of MoOx films and back surface recombination velocity of <100 cm/s at p-Si/MoOx.