Carrier density and lifetime for different dopants in single-crystal and polycrystalline CdTe

Burst, James M.; Farrell, S.; Albin, David S.; Colegrove, Eric; Reese, Matthew O.; Duenow, Joel N.; Kuciauskas, Darius; Metzger, Wyatt K.

doi:10.1063/1.4966209

Cited by 56 publications

(26 citation statements)

References 53 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The V Cd intrinsic defect forms an acceptor, and electron paramagnetic resonance estimates a transition energy within 0.47 eV above the valence band maximum 18 , 19 . Measured levels of intrinsically-formed acceptor concentration are often <10 16 cm −3 in single crystal material 20 which is substantially lower than expected from stoichiometric deviation, and higher levels are often not stable 21 . The problem is that while the desired V Cd defect formation is favored, compensating antisite defects such as Te Cd are also favored, leading to the neutral defect V Cd -Te Cd .…”

Section: Resultsmentioning

confidence: 80%

“…In CdTe photovoltaics, a Group V doping approach on the anion site has received little attention until recently. Substitutional defects using P, As, and Sb on Te lattice sites form shallow acceptors with estimated transition energies for (0/-) of 0.07 eV, 0.10 eV, and 0.23 eV above the valence band maximum 21 , 25 , as listed in Table 1 . In this scenario, the challenge is ensuring that both sufficient V Te sites exist and that dopant substitution dominates over interstitial occupancy.…”

Section: Resultsmentioning

confidence: 99%

See 1 more Smart Citation

Overcoming Carrier Concentration Limits in Polycrystalline CdTe Thin Films with In Situ Doping

McCandless

Buchanan

Thompson

et al. 2018

Sci Rep

Self Cite

View full text Add to dashboard Cite

Thin film materials for photovoltaics such as cadmium telluride (CdTe), copper-indium diselenide-based chalcopyrites (CIGS), and lead iodide-based perovskites offer the potential of lower solar module capital costs and improved performance to microcrystalline silicon. However, for decades understanding and controlling hole and electron concentration in these polycrystalline films has been extremely challenging and limiting. Ionic bonding between constituent atoms often leads to tenacious intrinsic compensating defect chemistries that are difficult to control. Device modeling indicates that increasing CdTe hole density while retaining carrier lifetimes of several nanoseconds can increase solar cell efficiency to 25%. This paper describes in-situ Sb, As, and P doping and post-growth annealing that increases hole density from historic 1014 limits to 1016–1017 cm−3 levels without compromising lifetime in thin polycrystalline CdTe films, which opens paths to advance solar performance and achieve costs below conventional electricity sources.

show abstract

Section: Resultsmentioning

confidence: 80%

Section: Resultsmentioning

confidence: 99%

Overcoming Carrier Concentration Limits in Polycrystalline CdTe Thin Films with In Situ Doping

McCandless

Buchanan

Thompson

et al. 2018

Sci Rep

Self Cite

View full text Add to dashboard Cite

show abstract

“…This can reduce harmful Te on Cd (Te Cd ) antisites that may limit lifetime, improve stability, and increase hole density compared to traditional Cu and Te-rich chemistries [9]. Continuing to build fundamental understanding is critical.…”

Section: Introductionmentioning

confidence: 99%

Experimental and theoretical comparison of Sb, As, and P diffusion mechanisms and doping in CdTe

Colegrove

Yang

Harvey

et al. 2018

J. Phys. D: Appl. Phys.

View full text Add to dashboard Cite

Fundamental material doping challenges have limited CdTe electro-optical applications. In this work, the As atomistic diffusion mechanisms in CdTe are examined by spatially resolving dopant incorporation in both single-crystalline and polycrystalline CdTe over a range of experimental conditions. Densityfunctional theory calculations predict experimental activation energies and indicate As diffuses slowly through the Te sublattice and quickly along GBs similar to Sb. Because of its atomic size and associated defect chemistry, As does not have a fast interstitial diffusion component similar to P. Experiments to incorporate and activate P, As, and Sb in polycrystalline CdTe are conducted to examine if ex-situ Group V doping can overcome historic polycrystalline doping limits. The distinct P, As, and Sb diffusion characteristics create different strategies for increasing hole density. Because fast interstitial diffusion is prominent for P, less aggressive diffusion conditions followed by Cd overpressure to relocate the Group V element to the Te lattice site is effective. For larger atoms, slower diffusion through the Te sublattice requires more aggressive diffusion, however further activation is not always necessary. Based on the new physical understanding, we have obtained greater than 10 16 cm -3 hole density in polycrystalline CdTe films by As and P diffusion.

show abstract

“…Group I dopants tend to self-compensate, and while they can be incorporated at low temperatures due to fast diffusion, the fast diffusion also creates stability issues and self-compensation that can limit hole density [1][2][3][4][5]. Furthermore, these elements form somewhat deep acceptors [6], 100-200 meV above the valance band, which can reduce lifetime [7,8] in addition to the lifetime reducing mid-gap states associated with Te-rich stoichiometry. In CdTe solar technology, the use of Cl and Cu as dopants or passivants has failed to produce hole density greater than 10 15 cm -3 and contributed to the stagnation of open-circuit voltage (V OC ) for 30 years [9][10][11].…”

Section: Introductionmentioning

confidence: 99%

“…Recent results have indicated that CdTe with Group V dopants placed substitutionally on the Te lattice sites can achieve radiatively limited lifetimes and hole concentrations exceeding 10 17 cm -3 [13]. Early data also suggest that Group V dopants appear to remain more stable [8]; however, incorporating these elements is more difficult.…”

Section: Introductionmentioning

confidence: 99%

Phosphorus Diffusion Mechanisms and Deep Incorporation in Polycrystalline and Single-Crystalline CdTe

Colegrove¹,

Harvey²,

Yang³

et al. 2016

Phys. Rev. Applied

Self Cite

View full text Add to dashboard Cite

A key challenge in cadmium telluride (CdTe) semiconductors is obtaining stable and high hole density. Group I elements substituting Cd can form acceptors but easily self-compensate and diffuse quickly. For example, CdTe photovoltaics have relied on copper as a dopant, but this creates stability problems and hole density that has not exceeded 10 15 cm-3. If hole density can be increased beyond 10 16 cm-3 , CdTe solar technology can exceed multicrystalline silicon performance and provide levelized costs of electricity below conventional energy sources. Group V elements substituting Te offer a solution, but they are very difficult to incorporate. Using time-of-flight secondary-ion mass spectrometry, we examine bulk and grain boundary (GB) diffusion of phosphorous (P) in CdTe in Cd-rich conditions. We find that in addition to slow bulk diffusion and fast GB diffusion, there is a critical fast bulk diffusion component that enables deep P incorporation in CdTe. Detailed first-principles calculations indicate the slow bulk diffusion component is caused by substitutional P diffusion through the Te sublattice, whereas the fast bulk diffusion component is caused by P diffusing through interstitial lattice sites following the combination of a kick-out step and two rotation steps. The latter is limited in magnitude by high formation energy, but is sufficient to manipulate P incorporation. In addition to an increased physical understanding, this result opens up new experimental possibilities for Group V doping in CdTe applications.

show abstract

Carrier density and lifetime for different dopants in single-crystal and polycrystalline CdTe

Cited by 56 publications

References 53 publications

Overcoming Carrier Concentration Limits in Polycrystalline CdTe Thin Films with In Situ Doping

Overcoming Carrier Concentration Limits in Polycrystalline CdTe Thin Films with In Situ Doping

Experimental and theoretical comparison of Sb, As, and P diffusion mechanisms and doping in CdTe

Phosphorus Diffusion Mechanisms and Deep Incorporation in Polycrystalline and Single-Crystalline CdTe

Contact Info

Product

Resources

About