Published online by Cambridge University Press: 28 August 2013
We have studied Cu2S absorber layers prepared by physical vapor deposition (PVD) by calibrated spectral photoluminescence (PL) and by confocal PL as function of temperature T and excitation fluxes to obtain the absolute PL-yield at an excitation flux equivalent to the AM1.5 spectrum and to calculate the splitting of the quasi-Fermi levels (QFL) µ = Ef,n-Ef,p and the absorption coefficient α(E), both in the temperature range 20 K ≤ T ≤ 400 K. The PL-spectra reveal two peaks at E1 = 1.17 eV and E2 = 1.3 eV, of which the low energy peak is only detectable at temperatures T < 200 K. The samples show an impressive QFL-splitting of µ > 700 meV at 300 K associated with a pseudo band gap of Eg = 1.25 eV. The high energy peak shows an unexpected temperature behavior, namely an increase of the PL-yield with rising temperature at variance with the behavior of QFL-splitting that decreases with rising T from extrapolated T = 0K value of µ = 1.3 eV. The PL-yield versus temperature will be discussed in terms of different defect states in the band gap. Our observations indicate that, contrary to common believe, it is not the PL-yield, but rather the QFL-splitting that is the comprehensive indicator of the quality of the excited state in an illuminated semiconductor. A further examination of the lateral variation of the opto-electronic properties by confocal PL shows a strong correlation between the QFL-splitting, the Urbach energy EU and the optical band gap Eopt, respectively.
To send this article to your Kindle, first ensure no-reply@cambridge.org is added to your Approved Personal Document E-mail List under your Personal Document Settings on the Manage Your Content and Devices page of your Amazon account. Then enter the ‘name’ part of your Kindle email address below. Find out more about sending to your Kindle. Find out more about saving to your Kindle.
Note you can select to save to either the @free.kindle.com or @kindle.com variations. ‘@free.kindle.com’ emails are free but can only be saved to your device when it is connected to wi-fi. ‘@kindle.com’ emails can be delivered even when you are not connected to wi-fi, but note that service fees apply.
Find out more about the Kindle Personal Document Service.
To save this article to your Dropbox account, please select one or more formats and confirm that you agree to abide by our usage policies. If this is the first time you used this feature, you will be asked to authorise Cambridge Core to connect with your Dropbox account. Find out more about saving content to Dropbox.
To save this article to your Google Drive account, please select one or more formats and confirm that you agree to abide by our usage policies. If this is the first time you used this feature, you will be asked to authorise Cambridge Core to connect with your Google Drive account. Find out more about saving content to Google Drive.