Dual-liquid-junction photoelectrochemistry and finite-element computational modeling quantified the effect on open-circuit photovoltage, Voc, of varying barrier heights at the back, traditionally ohmic contact to a semiconductor. Variations in experimental back-contact barrier heights included changes in the redox potential energy of the contacting phase afforded by a series of nonaqueous, metallocene-based redox couples that demonstrate facile, one-electron transfer and dipole-based band edge shifts due changes in the chemical species at the semiconductor surface. Variation in semiconductor surface chemistry included hydrogen-terminated Si(111) as well as methyl-terminated Si(111) that yields a shift in band-edge alignment of ~0.3 eV relative to hydrogen termination. While methylation of n-Si improves Voc values at rectifying contacts, methylation at an ohmic contact has a deleterious impact on Voc values. We discuss the present experimental and computational results in the context of non-ideal semiconductor contacts.
Russell, M. A., Kalan, R. E., Pugliese, A. J., Carl, A. D., Masucci, C. P., Strandwitz, N. C., & Grimm, R. L. (2019). Dual liquid junction photoelectrochemistry: part II. open-circuit photovoltage variations due to surface chemistry, interfacial dipoles, and non-ohmic junctions at back contacts. Journal of The Electrochemical Society, 166(13). https://doi.org/10.1149/2.0541913jes
*denotes a WPI undergraduate student author