| 1. |
- Salome, Pedro M. P., et al.
(författare)
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A comparison between thin film solar cells made from co-evaporated CuIn1-xGaxSe2 using a one-stage process versus a three-stage process
- 2015
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Ingår i: Progress in Photovoltaics. - : Wiley. - 1062-7995 .- 1099-159X. ; 23:4, s. 470-478
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Tidskriftsartikel (refereegranskat)abstract
- Until this day, the most efficient Cu(In,Ga)Se-2 thin film solar cells have been prepared using a rather complex growth process often referred to as three-stage or multistage. This family of processes is mainly characterized by a first step deposited with only In, Ga and Se flux to form a first layer. Cu is added in a second step until the film becomes slightly Cu-rich, where-after the film is converted to its final Cu-poor composition by a third stage, again with no or very little addition of Cu. In this paper, a comparison between solar cells prepared with the three-stage process and a one-stage/in-line process with the same composition, thickness, and solar cell stack is made. The one-stage process is easier to be used in an industrial scale and do not have Cu-rich transitions. The samples were analyzed using glow discharge optical emission spectroscopy, scanning electron microscopy, X-ray diffraction, current-voltage-temperature, capacitance-voltage, external quantum efficiency, transmission/reflection, and photoluminescence. It was concluded that in spite of differences in the texturing, morphology and Ga gradient, the electrical performance of the two types of samples is quite similar as demonstrated by the similar J-V behavior, quantum spectral response, and the estimated recombination losses.
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| 2. |
- Teixeira, Jennifer P., et al.
(författare)
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Recombination Channels in Cu(In,Ga)Se2 Thin Films : Impact of the Ga-Profile
- 2020
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Ingår i: The Journal of Physical Chemistry C. - : American Chemical Society (ACS). - 1932-7447 .- 1932-7455. ; 124:23, s. 12295-12304
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Tidskriftsartikel (refereegranskat)abstract
- Depth bandgap profiles via a [Ga]/([Ga]+[In]) variation in the Cu(In,Ga)Se-2 (CIGS) absorber layer have been implemented as a strategy to enhance the performance of CIGS solar cells. Since the [Ga]/([Ga]+[In]) determines to a large extent the position of the conduction band minimum, different Ga-profiles lead to different electronic energy levels structures throughout the CIGS layer. In this paper, from the investigation of the dependence of the photoluminescence (PL) on excitation power and temperature, we critically analyze the impact of a notch or a linear Ga-profile on the CIGS electronic energy levels structure and subsequent dominant recombination channels. Notwithstanding, two radiative transitions involving fluctuating potentials were observed for each sample, and significant differences in the luminescence resulting from the two Ga-profiles were identified. For the CIGS absorber with a notch Ga-profile, two tail-impurity radiative transitions involving equivalent donor clusters and the same deep acceptor level were ascribed to the CIGS/CdS interface region and to the notch region. The probability of radiative recombination in these two regions is discussed. For the CIGS absorber with a linear Ga-profile, two band-impurity radiative transitions involving an acceptor, with an ionization energy compatible with the V-Cu defect were ascribed to the CIGS/CdS interface region. Our results show that the dominant acceptor defects are dependent on the Ga-profile, and they also highlight the complexity of the radiative and nonradiative recombination channels revealed by the tight control of the parameters in the experiment.
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