External Quantum Efficiency EQE Spectra

The semiconductor-electrolyte junction is essentially an analog of the junction that is formed in a solid-state device such as a solar cell. For this reason, measurements of the EQE as a function of photon energy can be used to obtain information 

As-deposited CdTe films are n-type, so that no heterojunction is formed between the CdTe and the underlying n-type CdS. When the as-deposited CdTe film on CdS is contacted with an electrolyte and is polarized so that a depletion layer forms at the n-CdTe-electrolyte junction, electron-hole pairs generated by illumination are separated, with the holes moving towards the electrolyte interface where they 

EQE spectrum shows a maximum near the band edge, but almost no response at higher energies. This indicates that the active junction is indeed located at the CdTe-electrolyte interface, since light can only penetrate through to the CdTe-electrolyte interface from the substrate side when the absorption coefficient of the CdTe is sufficiently low, as is the case near the band edge. 

Type conversion has also been foUowed as a function of annealing time by measuring EQE spectra. Eigure 1.35 iUustrates how the SS EQE spectra ofa 0.5 pm CdTe film on CdS/ETO evolve as the film is annealed. The results show that internal p-n junction is formed after 5 minutes and improves further with 

EQE spectra can be analyzed to obtain the bandgap of absorber materials. The photocurrent response (Jphoto) of the semiconductor electrolyte junction is described by the Gartner equation [148] as 

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