Mechanism of Electrical Passivation of Silicon Surfaces with Quinhydrone

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.

University of Delaware, Newark, DE 19716

AbstractThis work further explores the bonding mechanism of QHY/ME passivation. The two constituent parts p-benzoquinone(BQ) and hydroquinone(HQ) were studied separately. BQ was believed to abstract the hydrogen atom from methanol to become QH*. Both QH* and the resulting methanol radical are responsible for the large, instantaneous increase in lifetime in BQ/ME. HQ releases a proton to become QH*, which is also pH sensitive. Degradation of BQ/ME passivation in solution was also studied. Density functional theory (DFT) confirmed the proposed bonding mechanism and proved that the “edge-on” configuration is more energetically favorable than the “face-on” configuration.

Meixi Chen, Nicole Kotulak, Jimmy Hack, Abhishek Iyer, Kevin Jones, Robert Opila

XPS: the bonding of aromatic groups to the surfaces

Free radicals are an intrinsic part of the passivation.

single-bonded “edge-on” double-bonded “face-on”

127 KJ/mol higher

Quinhydrone (QHY) is a 1:1 mixture of p-benzoquinone (BQ) and hydroquinone (HQ).

A slow continuous deterioration of lifetime in BQ/ME is observed even when wafers are still immersed in solution.

DFT

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lifetime tester Sinton

Experimental process

ConclusionRadicals and protons are both intrinsic part in QHY/ME passivation. Being a simple, fast and friendly electronic passivation technique, QHY/ME passivation can be easily implemented into the future solar cell design, as well as the ingot/wafer testing in quality control.