Carrier selective solution processed molybdenum oxide silicon heterojunctions solar cells with over 12% efficiency

Abstract

Abstract We have fabricated and characterized the performance of carrier selective molybdenum oxide (MoO x )/n-Si heterojunction solar cells (HSCs), with the MoO x prepared by both E-beam evaporation (e-MoO x ) and solution process (s-MoO x ) techniques. The s-MoO x /Si HSC demonstrates the best power conversion efficiency of 12.5 %, with an open circuit voltage of 555 mV, short circuit current density of 33.3 mA cm −2 , and fill factor of 67.4% and it is higher than the efficiencies reported to date for s-MoO x /Si HSC. The efficiency achieved is approaching the 13.3% obtained for the e-MoO x /Si HSC. The slightly lower efficiency of s-MoO x /Si HSC is attributed to its carrier extraction loss arising from a higher contact resistivity at the MoO x /n-Si interface. This is also reflected in the selectivity of the contacts, which measures 10.1 for the s-MoO x contact, relative to 11.5 for the e-MoO x contact. Trap-assisted tunneling at the interface is believed to be the main mechanism that influences the cell performance such as open circuit voltage and fill factor, and results in a high ideality factor of ∼3.