Dependence of carrier lifetime on Cu-contacting temperature and ZnTe:Cu thickness in CdS/CdTe thin film solar cells

Gessert, T. A.; Metzger, Wyatt K.; Dippo, P.; Asher, S.; Dhere, R. G.; Young, Matthew R.

doi:10.1016/j.tsf.2008.11.008

Cited by 108 publications

(50 citation statements)

References 7 publications

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“…Low-resistivity contacts to p-CdTe layers are dicult to manufacture. The problem can be solved by depositing p-type ZnTe layer with high carrier concentration of 10 18 10 19 cm −3 [3,4]. On the other hand, p-ZnTe forms heterojunction with n-type CdTe.…”

Section: Introductionmentioning

confidence: 99%

Electrical Properties of p-ZnTe/n-CdTe Photodiodes

et al. 2012

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Currentvoltage (I V ) and capacitancevoltage (C V ) characteristics of photovoltaic, thinlm p-ZnTe/ n-CdTe heterojunctions have been studied in the temperature range of 280400 K. The pn junctions were grown by MBE on (100) semi-insulating GaAs substrates. From the analysis of IV and CV curves the potential barrier height of the junctions and its temperature dependence are determined. The relatively large value of the temperature coecient of the potential barrier height (2.53.0 × 10 −3 eV/K) indicates a high density of defects at the p-ZnTe/n-CdTe interface. The presence of interface defects limits the eciency of the solar energy conversion of these devices.

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Section: Introductionmentioning

confidence: 99%

Electrical Properties of p-ZnTe/n-CdTe Photodiodes

et al. 2012

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“…Originally, Cu has been added to the back contact of CdTe solar cells with the purpose of improving the contact properties of CdTe by forming a degenerate semiconductor layer, for example, in the form of Cu x Te, Cu-doped ZnTe, HgTe:CuTe-doped graphite paste or As 2 Te 3 :Cu 5, [21][22][23][24] . During back contact processing, part of the Cu has also been found to diffuse into CdTe 25,26 , where it increases acceptor concentration and affects carrier lifetime. In substrate configuration Cu is commonly added to the devices using the same approach as developed for devices in superstrate configuration, that is, the use of a Cu-containing layer with an equivalent Cu thickness of several nanometres in the electrical back contact structure 15,16,18 .…”

mentioning

confidence: 99%

Doping of polycrystalline CdTe for high-efficiency solar cells on flexible metal foil

et al. 2013

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Roll-to-roll manufacturing of CdTe solar cells on flexible metal foil substrates is one of the most attractive options for low-cost photovoltaic module production. However, various efforts to grow CdTe solar cells on metal foil have resulted in low efficiencies. This is caused by the fact that the conventional device structure must be inverted, which imposes severe restrictions on device processing and consequently limits the electronic quality of the CdTe layer. Here we introduce an innovative concept for the controlled doping of the CdTe layer in the inverted device structure by means of evaporation of sub-monolayer amounts of Cu and subsequent annealing, which enables breakthrough efficiencies up to 13.6%. For the first time, CdTe solar cells on metal foil exceed the 10% efficiency threshold for industrialization. The controlled doping of CdTe with Cu leads to increased hole density, enhanced carrier lifetime and improved carrier collection in the solar cell. Our results offer new research directions for solving persistent challenges of CdTe photovoltaics.

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“…Calculations were made for the surface recombination velocities S f = 10 7 cm/ s and S f = 0 at the front surface of the CdTe layer. The lifetimes of the charge carriers are assumed to be 10 -10 , 5 9 10 -10 and 2 9 10 -9 s based on the fact that, according to published data, the lifetimes of the charge carriers in thinfilm CdTe are usually in the range from 10 -10 s to 2 9 10 -9 s [48][49][50]. In calculations we use the mobilities of electrons and holes, which in thin-film CdTe are often taken to be 320 and 40 cm 2 /(V s), respectively [51,52].…”

Section: Recombination Losses and Requirements Imposed On Thickness Omentioning

confidence: 99%

“…These results were obtained with CdTe layer thickness d = 10 lm. Having fixed the value of W = 0.3 lm and the recombination velocity at the rear surface of the CdTe layer S b = 10 7 cm/s let us consider how the J sc value will change with decreasing the film thickness d. In the following calculations, we will accept the charge carrier lifetime equal to 2 9 10 -9 s (which is a realistic assumption [48][49][50]) because its shortening leads to a significant reduction of the short-circuit current. Figure 15 shows the results of such calculations of relative decreasing J sc (in percentage).…”

Section: Losses Due To Decrease In the Thickness Of The Cdte Layer Anmentioning

confidence: 99%

Possibilities to decrease the absorber thickness reducing optical and recombination losses in CdS/CdTe solar cells

Kosyachenko

2013

Mater Renew Sustain Energy

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Based on the optical constants, calculations of optical losses in CdS/CdTe solar cells have been carried out taking into account reflections at the interfaces and absorption in the TCO and CdS layers. It has been shown that the losses caused by reflections at the interfaces result in lowering the short-circuit current by *9 %, whereas absorption in the TCO and CdS layers with the typical thicknesses lead to losses of 15-24 %. Calculations of the integrated absorptive capacity of CdTe layer taking into account the spectral distributions of the standard AM1.5 solar radiation and the absorption coefficient of CdTe have been carried out. It is shown that in CdTe, the almost complete absorption of photons (C99.9 %) in the hv [ E g range is observed at a layer thickness of more than 20-30 lm, and the absorptive capacity of photons in a CdTe layer of thickness 1 lm is about 93 %. Based on the continuity equation and taking into account the recombination at the front and rear surfaces of the CdTe layer as well as in the space charge region, the restrictions imposed on the thickness of the absorber layer in CdS/CdTe heterojunction are studied. In all cases, along with the mobilities and lifetimes of charge carriers, the concentration of uncompensated impurities in CdTe plays a key role in the generation of photocurrent. When the CdTe absorber layer is thin (\1 lm), it is impossible to avoid a noticeable decrease of the short-circuit current density. The losses of the short-circuit current are equal to 19-20 % when the thickness of the CdTe layer is 0.5 lm whereas only 5 % for a typical thickness of 2-3 lm.

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Dependence of carrier lifetime on Cu-contacting temperature and ZnTe:Cu thickness in CdS/CdTe thin film solar cells

Cited by 108 publications

References 7 publications

Electrical Properties of p-ZnTe/n-CdTe Photodiodes

Electrical Properties of p-ZnTe/n-CdTe Photodiodes

Doping of polycrystalline CdTe for high-efficiency solar cells on flexible metal foil

Possibilities to decrease the absorber thickness reducing optical and recombination losses in CdS/CdTe solar cells

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