000049633 001__ 49633
000049633 005__ 20240712084503.0
000049633 0247_ $$2Handle$$a2128/528
000049633 0247_ $$2URI$$a528
000049633 0247_ $$2ISSN$$a1433-5522
000049633 020__ $$a3-89336-401-3
000049633 037__ $$aPreJuSER-49633
000049633 041__ $$aEnglish
000049633 082__ $$a620
000049633 1001_ $$0P:(DE-Juel1)VDB14656$$aMerdzhanova, Tsvetelina$$b0$$eCorresponding author$$gfemale$$uFZJ
000049633 245__ $$aMicrocrystalline silicon films and solar cells investigated by photoluminescence spectroscopy
000049633 260__ $$aJülich$$bForschungszentrum Jülich GmbH Zentralbibliothek, Verlag$$c2005
000049633 300__ $$aX, 137 S.
000049633 3367_ $$0PUB:(DE-HGF)11$$2PUB:(DE-HGF)$$aDissertation / PhD Thesis
000049633 3367_ $$0PUB:(DE-HGF)3$$2PUB:(DE-HGF)$$aBook
000049633 3367_ $$02$$2EndNote$$aThesis
000049633 3367_ $$2DRIVER$$adoctoralThesis
000049633 3367_ $$2BibTeX$$aPHDTHESIS
000049633 3367_ $$2DataCite$$aOutput Types/Dissertation
000049633 3367_ $$2ORCID$$aDISSERTATION
000049633 4900_ $$0PERI:(DE-600)2414930-5$$823177$$aSchriften des Forschungszentrums Jülich. Reihe Energietechnik / Energy Technology$$v41
000049633 502__ $$aAcademy of Science, Sofia, Diss., 2004$$bDr. (FH)$$cAcademy of Science, Sofia$$d2004
000049633 500__ $$aRecord converted from VDB: 12.11.2012
000049633 520__ $$aA systematic investigation on photoluminescence (PL) properties of microcrystalline silicon ($\mu$c-Si :H) films with structural composition changing from highly crystalline to predominantly amorphous is presented. The samples were prepared by PECVD and HWCVD with different silane concentration in hydrogen (SC). By using photoluminescence in combination with Raman spectroscopy the relationship between electronic properties and the microstructure of the material is studied. The PL spectra of gc-Si :H reveal a rather broad ($\thicksim$0.13eV) featureless band at about 1 eV (`$\mu$c'-Si-band) . In mixed phase material of crystalline and amorphous regions, a band at about 1.3eV with halfwidth of about 0.3eV is found in addition to `$\mu$c'-Si-band, which is attributed to the amorphous phase (`a'-Si-band). Similarly to amorphous silicon, the `$\mu$c'-Si-band is assigned to recombination between electrons and holes in band tail states. An additional PL band centred at about 0.7eV with halfwidth slightly broader than the `$\mu$c'-Si-band is observed only for films prepared at high substrate temperature and it is preliminarily assigned to defect-related transitions as in polycrystalline silicon. With decreasing crystalline volume fraction, the `$\mu$c'-Si-band shifts continuously to higher energies for all $\mu$c-Si :H films but the linewidth of the PL spectra is almost unaffected. This is valid for all deposition conditions investigated. The results are interpreted, assuming decease of the density of band tail states with decreasing crystalline volume fraction. The reason for the band tails and their reduction is not clear but strain might play a critical role and hydrogen or hydrogenated amorphous silicon might be effective for strain reduction. By applying the `carrier thermalization model' developed for a-Si:H the slope, E$_{o}$, of the conduction band tail states are derived from temperature dependence of the PL intensity quenching (E$_{o}$ $\approx$ 0.035eV) and from the shift of the PL peak energy (E $\approx$ 0.022eV). The reason for this discrepancy is not clear yet, but the simple model assuming that only one type of carriers are involved in the process of thermal excitation might be too simple for ~$\mu$c-Si :H. By using a new technique, namely voltage modulated PL on solar cells, information on the carrier distributions is obtained. It relates the splitting of the quasi-Fermi-levels of electrons and holes and the respective excess carrier distributions via open circuit voltage V$_{oc}$ and the PL energy. This relationship is studied as a function of SC, temperature and optical generation rate go. An increase of the PL energy and V$_{oc}$ is found for (i) increasing SC, (ii) increasing go and (iii) decreasing temperature. It is suggested that the reason in all cases is the shift of the distribution of electrons and holes to higher energies. We propose that with increasing SC, the density of band tail states is reduced and the carrier distributions shift to higher energies as a result of an increasing generation rate and increasing carrier lifetime with decreasing temperature, respectively. The shift of quasi-Fermi levels to higher energies is always accompanied by a weak shift of carrier distributions in the band tails. It is concluded that the maximum achievable V_ and the PL peak energy are determined by the band tail states. At low temperature, a strongly reduced carrier extraction is observed, which indicates reduced a drift or a diffusion length. Multiple trapping processes in the band tail states are suggested as the reason for this. A simple model is proposed to simulate PL spectra and V$_{oc}$ in $\mu$c-Si:H solar cells as a function of temperature, based on carrier distributions in quasi-equilibrium conditions. In the model is assumed symmetric density of states distributions for electrons and holes in the conduction and the valence band tail states. The best agreement between the model calculations and experimental results for two solar cells with different structural properties was obtained by using a E$_{o}$ $\approx$ 0.03eV for the slope of both exponential band tail states, which fits reasonably well with E$_{o}$ $\approx$ 0.035eV from the temperature dependence of the luminescence intensity.
000049633 536__ $$0G:(DE-Juel1)FUEK247$$2G:(DE-HGF)$$aPhotovoltaik$$cE02$$x0
000049633 655_7 $$aHochschulschrift$$xDissertation (FH)
000049633 8564_ $$uhttps://juser.fz-juelich.de/record/49633/files/Energietechnik_41.pdf$$yOpenAccess
000049633 909CO $$ooai:juser.fz-juelich.de:49633$$pdnbdelivery$$pVDB$$pdriver$$popen_access$$popenaire
000049633 915__ $$0StatID:(DE-HGF)0510$$2StatID$$aOpenAccess
000049633 9141_ $$y2005
000049633 9131_ $$0G:(DE-Juel1)FUEK247$$bEnergie$$kE02$$lErneuerbare Energien$$vPhotovoltaik$$x0
000049633 920__ $$lyes
000049633 9201_ $$0I:(DE-Juel1)VDB46$$d31.12.2006$$gIPV$$kIPV$$lInstitut für Photovoltaik$$x1
000049633 970__ $$aVDB:(DE-Juel1)77644
000049633 9801_ $$aFullTexts
000049633 980__ $$aVDB
000049633 980__ $$aJUWEL
000049633 980__ $$aConvertedRecord
000049633 980__ $$aphd
000049633 980__ $$aI:(DE-Juel1)IEK-5-20101013
000049633 980__ $$aUNRESTRICTED
000049633 980__ $$aFullTexts
000049633 981__ $$aI:(DE-Juel1)IMD-3-20101013
000049633 981__ $$aI:(DE-Juel1)IEK-5-20101013