Prospects for in situ junction formation in CuInSe2 based solar cells

Ramanathan, K.; Noufi, R.; Granata, Jennifer E; Webb, Jennifer M.; Keane, J.

doi:10.1016/s0927-0248(98)00042-7

Cited by 55 publications

(30 citation statements)

References 3 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…All samples with the standard 50 nm CdS buffer show the typical depth-dependence of the dopant concentration already observed in Fig. 2 [13][14][15][16][17][18][19]. Note that the increase in dopant concentration towards smaller apparent depth, i.e., in stronger forward bias, most likely is a measurement artifact due to additional equivalent circuit elements as mentioned above.…”

Section: Capacitance-voltage Analysismentioning

confidence: 53%

“…Theoretical calculations show that Cd acts as a donor in CIGSe [12][13][14], which would thus lead to an increased compensation ratio near the CIGSe/CdS interface and accordingly reduce the net doping in the space charge region. Several studies provide direct evidence for Cd in-diffusion into CIGSe, at least within a few tens of nanometers from the CdS/CIGSe interface [15][16][17][18][19]. Note however, that parts-permillion concentrations of electrically active Cd are sufficient to significantly affect the net doping, which is well below typical detection limits.…”

Section: Capacitance-voltage Analysismentioning

confidence: 99%

See 1 more Smart Citation

What is the dopant concentration in polycrystalline thin-film Cu(In,Ga)Se 2 ?

et al. 2017

View full text Add to dashboard Cite

We compare the dopant concentration of polycrystalline Cu(In,Ga)Se 2 thin film absorbers derived from Hall and capacitance-voltage measurements. Although both measurements techniques appear to be reliable, dopant concentrations determined by capacitance-voltage analysis are significantly lower and vary with probing depth into the absorber. The doping profiles and differences between both measurement techniques are consistent with Cd in-diffusion from the CdS buffer layer during solar cell fabrication. Different doping profiles obtained after a variation of the CdS deposition process support this scenario.

show abstract

Section: Capacitance-voltage Analysismentioning

confidence: 53%

Section: Capacitance-voltage Analysismentioning

confidence: 99%

What is the dopant concentration in polycrystalline thin-film Cu(In,Ga)Se 2 ?

et al. 2017

View full text Add to dashboard Cite

show abstract

“…Abou-Ras et al [8] suggested that the absence of a Cd doping layer on the CIGS surface in PVD-CdS/CIGS heterojunctions, and thus the lack of a p-n homojunction, may explain the efficiency deficit. Indeed, Ramanathan et al [9,10] showed that Cd insertion into the CIGS surface may hold the key to the success of CBD-CdS/CIGS solar cells by comparing the efficiencies of a series of CIGS solar cell devices in which the CIGS surfaces were treated in different CBD solutions. Although the Cd-doped CIGS surface in CBD-CdS/CIGS junction has been experimentally verified [11,12], no direct evidence of Cd doping on the CIGS surface in PVD-CdS/CIGS is available.…”

Section: Introductionmentioning

confidence: 99%

Intermixing and Formation of Cu-Rich Secondary Phases at Sputtered CdS/CuInGaSe₂Heterojunctions

Varley

Ercius

et al. 2016

IEEE J. Photovoltaics

View full text Add to dashboard Cite

We report on direct evidence of Cd doping of the CuInGaSe2 (CIGS) surface in physical vapor deposited (PVD) CdS/CIGS heterojunctions by scanning transmission electron microscopy (STEM) and related techniques. We find Cd doping of the CIGS nearsurface region regardless of the presence or absence of Cu rich domains in the CdS for both zinc-blende (zb) and wurtzite (wz) CdS. However, we find that the Cd penetrates much farther into the CIGS when Cu-rich domains are present in the CdS. This suggests that Cu exchanges with Cd, increasing the concentration gradient for Cd in the CIGS and thus driving Cd into the CIGS surface. The Cd doping is clearly resolved at atomic resolution in aberration-corrected STEM-high angle annular dark field images. In zb-CdS/CIGS heterojunctions, Cd is shown to substitute for both Cu and Ga atoms, while in wzCdS/CIGS heterojunctions Cd seems to predominantly occupy Cu sites. Cd doping in the CIGS surface layer suggests the formation of a p-n homojunction in the CIGS, which may account for the high device efficiencies, comparable to CBD-CdS/CIGS processed structures.

show abstract

“…At the same time, doping of CdS by Cu increases its conductivity. 6 Additionally, Cd diffuses from the CdS into the CIGSe layer, occupying Cu vacancies in the near-interface region, acting as substitutional donor, 20 contributing even more to the CIGSe conductivity-type inversion at the CdS / CIGSe interface. In the case of the airexposed samples the CIGSe surface is inverted by the presence of oxides: KPFM results show that ⌽ CIGSe-surface is lowered by more than half of the E g-CIGSe .…”

mentioning

confidence: 99%

Formation of the physical vapor deposited CdS∕Cu(In,Ga)Se2 interface in highly efficient thin film solar cells

Rusu

Glatzel

Neisser

et al. 2006

Applied Physics Letters

View full text Add to dashboard Cite

We report on the buffer/absorber interface formation in highly efficient ͑14.5%, air mass 1.5͒ ZnO/CdS/Cu͑In, Ga͒Se 2 solar cells with a physical vapor deposited CdS buffer. For Se-decapped Cu͑In, Ga͒Se 2 ͑CIGSe͒ absorbers we observe sulfur passivation of the CIGSe grain boundaries during CdS growth and at the interface a thermally stimulated formation of a region with a higher band gap than that of the absorber bulk, determining the height of the potential barrier at the CdS / CIGSe interface. For air-exposed CIGSe samples the grain boundary passivation is impeded by a native oxide/adsorbate layer at the CIGSe surface determining the thermal stability of the potential barrier height. © 2006 American Institute of Physics. ͓DOI: 10.1063/1.2190768͔ Cu͑In, Ga͒Se 2 ͑CIGSe͒ thin film solar cells achieve efficiencies up to 19.5% when using a "wet" chemical bath deposited ͑CBD͒ CdS buffer layer between the p-type absorber and the n-type ZnO window. 1 Surprisingly, CIGSe polycrystalline thin film solar cells exhibit higher internal quantum efficiencies ͑QEs͒ than devices from single crystalline CIGSe films. 2 Recent theoretical 3 and experimental 4 studies propose an explanation based on a model where Cu depleted polar grain boundary ͑GB͒ interfaces lead to a valence band offset between GB and grain interior ͑GI͒, repeling holes from the GB and thus diminishing GB recombination. Other experiments observed light induced changes in the conduction band at GBs. 5 Nevertheless, when a CdS buffer is deposited by a "dry" physical vapor deposition ͑PVD͒ the CI͑G͒Se solar cells show significantly lower efficiency. 6 The highest reported efficiency using a PVD-CdS is ϳ12.4%. 7 This shows that differently deposited CdS buffers provide differences at the related interfaces and finally in the device operation.In this Letter we show that ͑1͒ not only the initial state of the absorber GBs has a decisive role but that additionally a GB passivation process, which occurs during the CdS buffer deposition, enhances the absorber electronic properties; ͑2͒ the condition of the absorber surface strongly influences the passivation process and the potential barrier of recombination at the CdS / CIGSe interface; and ͑3͒ the preparation of highly efficient solar cells with PVD-CdS buffers is possible.CIGSe thin films ͓Ga/ ͑Ga+ In͒ =24%͔ were deposited by a three-stage coevaporation process 8 on Mo-coated soda lime glass substrates. An ϳ300 nm Se cap protection layer was deposited on top of the CIGSe absorber. Se decapping and in situ thermal deposition of a CdS layer from a single source were performed in an ultrahigh vacuum ͑UHV͒ ͑p ϳ 10 −9 mbar͒ system. Samples comparable to those in standard solar cell production were prepared by exposure to air for 40 min prior to CdS deposition. This results in the formation of Na 2 CO 3 and also of In 2 O 3 , Ga 2 O 3 , and SeO x native oxides at the absorber surface. 9 For the deposition of the CdS layers, the CdS source and substrate temperatures were kept constant at 680 and 100°C, respectively, providin...

show abstract

Prospects for in situ junction formation in CuInSe2 based solar cells

Cited by 55 publications

References 3 publications

What is the dopant concentration in polycrystalline thin-film Cu(In,Ga)Se 2 ?

What is the dopant concentration in polycrystalline thin-film Cu(In,Ga)Se 2 ?

Intermixing and Formation of Cu-Rich Secondary Phases at Sputtered CdS/CuInGaSe₂Heterojunctions

Formation of the physical vapor deposited CdS∕Cu(In,Ga)Se2 interface in highly efficient thin film solar cells

Contact Info

Product

Resources

About

Prospects for in situ junction formation in CuInSe2 based solar cells

Cited by 55 publications

References 3 publications

What is the dopant concentration in polycrystalline thin-film Cu(In,Ga)Se 2 ?

What is the dopant concentration in polycrystalline thin-film Cu(In,Ga)Se 2 ?

Intermixing and Formation of Cu-Rich Secondary Phases at Sputtered CdS/CuInGaSe2Heterojunctions

Formation of the physical vapor deposited CdS∕Cu(In,Ga)Se2 interface in highly efficient thin film solar cells

Contact Info

Product

Resources

About

Intermixing and Formation of Cu-Rich Secondary Phases at Sputtered CdS/CuInGaSe₂Heterojunctions