Role of oxide at interface between organic layer and silicon substrate in hybrid solar cells


Degradation in PEDOT:PSS-silicon hybrid heterojunction solar cells is centered at the organic–silicon interface characterized by an s-shaped JV curve. The effects of interfacial silicon oxide and the degradation of PEDOT:PSS films on solar cell performance were simulated and fit to experimental results and found to be good predictors of JV performance and the development of s-shapes. Transmission line measurement (TLM) studies showed the Ag-PEDOT:PSS interface remains ohmic over 5 weeks and has a contact resistivity < 0.1ohm cm2 over 10 days. X-ray photoelectron spectroscopy (XPS) showed that the interfacial silicon oxide develops rapidly after fabrication with high amounts of suboxide defects that grows and chemically saturates to the native oxide thickness (1.5 nm) and composition as the devices age. Hard X-ray photoelectron spectroscopy (HAXPES) was used to investigate the buried organic–silicon interface and showed that doping in the PEDOT:PSS backbone decreases and the PEDOT:PSS-silicon band alignment does not change measurably as the devices age.

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Work at the ASU Solar Power Lab by Som Dahal, Rameshwari Ghimire and Stuart Bowden, was supported by the Nanotechnology collaborative Infrastructure Southwest (NCI-SW) with funding from NSF- ECCS1542160. Electron beam deposition was done at UD Nanofabrication facility under guidance of Scott McCracken. TLM measurements were done under the guidance of Dr. Yuping Zeng and Peng Cui. XPS characterization was performed at The Surface Analysis Facility in the University of Delaware supported by the National Science Foundation grant number 1428149 and under the guidance of Wenbo Wu and with the help of Miyu Mudalamane. This research used resources of the National Synchrotron Light Source II, a US Department of Energy (DOE) Office of Science User Facility operated for the DOE Office of Science by Brookhaven National Laboratory under Contract No. DE-SC0012704. HAXPES measurements were performed at NIST beamline SST-2, located at NSLS-II under the guidance of Dr. Conan Weiland. This material is based upon work primarily supported by the Engineering Research Center Program of the National Science Foundation and the Office of Energy Efficiency and Renewable Energy of the Department of Energy under NSF Cooperative Agreement No. EEC‐1041895. Any opinions, findings, and conclusions or recommendations expressed in this material are those of the author(s) and do not necessarily reflect those of the National Science Foundation or Department of Energy.

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Angel Trujillo, D.A., Iyer, A., Hack, J. et al. Role of oxide at interface between organic layer and silicon substrate in hybrid solar cells. Journal of Materials Research (2021).

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