In Situ and Ex Situ Investigations of KF Postdeposition Treatment Effects on CIGS Solar Cells

Karki, Shankar; Paul, Pran K.; Rajan, Grace; Ashrafee, Tasnuva; Aryal, Krishna; Pradhan, Puja; Collins, R. W.; Rockett, Angus; Grassman, Tyler J.; Ringel, S. A.; Arehart, Aaron R.; Marsillac, Sylvain

doi:10.1109/jphotov.2016.2637659

Cited by 44 publications

(13 citation statements)

References 21 publications

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“…[3,17,18] In particular, 6 of the last 8 world record CIGS efficiencies have employed a KF (or RbF) PDT, [1,3,4,12,17,21] ultimately advancing the record efficiency from 20.3 to 22.6% in just ~3.5 yr. KF PDT successes in the laboratory have now been extended to commercially-relevant chalcogenized CIGS absorbers, [12] full size (0.75 m 2 ) modules, [13] and Cd-free Zn(O,S) buffers. [2,12,22] Although the mechanisms responsible for these efficiency improvements are not clear, the KF PDT has been associated with multiple phenomena: increased hole concentration (e.g., by consuming InCu compensating donors to produce KCu neutral defects [23] ), [5,7,8,11,14,15,19,[24][25][26][27] decreased hole concentration (by consuming NaCu to produce InCu compensating donors, [1] or by forming (K-K)Cu dumbbell interstitial donors [28] ), [1,8,10,16] Na depletion or formation of soluble Na chemical(s), [1,5,7,8,10,13,14,25,26,29,30] Ga depletion at the surface, [1, ...…”

Section: Introductionmentioning

confidence: 99%

Surface and bulk effects of K in highly efficient Cu1-xKxInSe2 solar cells

Muzzillo

Mansfield

et al. 2018

Solar Energy Materials and Solar Cells

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To advance knowledge of K bonding in Cu(In,Ga)(Se,S)2 (CIGS) photovoltaic (PV) absorbers, recent Cu-K-In-Se phase growth studies have been extended to PV performance. First, the effect of distributing K throughout bulk Cu1-xKxInSe2 absorbers at low K/(K+Cu) compositions (0 ≤ x ≤ 0.30) was studied.Efficiency, open-circuit voltage (VOC), and fill factor (FF) were greatly enhanced for x ~ 0.07, resulting in an officially-measured 15.0%-efficient solar cell, matching to the world record CuInSe2 efficiency. The improvements were a result of reduced interface and bulk recombination, relative to CuInSe2 (x ~ 0). However, higher x compositions had reduced efficiency, short-circuit current density (JSC), and FF due to greatly increased interface recombination, relative to the x ~ 0 baseline. Next, the effect of confining K at the absorber/buffer interface at high K/(K+Cu) compositions (0.30 ≤ x ≤ 0.92) was researched. Previous work showed that these surface layer growth conditions produced CuInSe2 with a large phase fraction of KInSe2. After optimization (75 nm surface layer with x ~ 0.41), these KInSe2 surface samples exhibited increased efficiency (officially 14.9%), VOC, and FF as a result of decreased interface recombination. The KInSe2 surfaces had features similar to previous reports for KF post-deposition treatments (PDTs) used in world record CIGS solar cells-taken as indirect evidence that KInSe2 can form during these PDTs. Both the bulk and surface growth processes greatly reduced interface recombination. However, the KInSe2 surface had higher K levels near the surface, greater lifetimes, and increased inversion near the buffer interface, relative to the champion bulk CKIS absorber. These characteristics demonstrate that K may benefit PV performance by different mechanisms at the surface and in the absorber bulk.Graphical abstract:

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Section: Introductionmentioning

confidence: 99%

Surface and bulk effects of K in highly efficient Cu1-xKxInSe2 solar cells

Muzzillo

Mansfield

et al. 2018

Solar Energy Materials and Solar Cells

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“…3 shows the DLTS spectra with one dominant trap with EV+0.57 eV activation energy and a minimum trap concentration of 7x10 15 cm -3 . Previously, with scanning-DLTS the E V +0.57 eV was found to be spatially localized and located only in specific intergrain regions [15][16][17]. The inset of Fig.…”

Section: Resultsmentioning

confidence: 76%

Fast C-V method to mitigate effects of deep levels in CIGS doping profiles

Paull

Bailey²,

Zapalac³

et al. 2017

2017 IEEE 44th Photovoltaic Specialist Conference (PVSC)

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In this work, methods to determine more accurate doping profiles in semiconductors is explored where trap-induced artifacts such as hysteresis and doping artifacts are observed. Specifically in CIGS, it is shown that this fast capacitance-voltage (C-V) approach presented here allows for accurate doping profile measurement even at room temperature, which is typically not possible due to the large ratio of trap concentration to doping. Using deep level transient spectroscopy (DLTS) measurement, the deep trap responsible for the abnormal C-V measurement above 200 K is identified. Importantly, this fast C-V can be used for fast evaluation on the production line to monitor the true doping concentration, and even estimate the trap concentration. Additionally, the influence of high conductance on the apparent doping profile at different temperature is investigated.

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“…[25] The incorporation of potassium and removal of sodium in the absorber layer was explained by an ion-exchange mechanism that favored the heavier K displacing the lighter Na for the given PDT conditions. [25] While the mechanisms via which potassium affects the performance of the CIGSSe absorber layer is still under debate, some of the KF-PDT induced changes include: i) formation of a passivating K-In-Ga-Se, [229,230] K-In-Se (E g ≈ 2.68 eV), [156,157,165] and In-Se surface layer, [230] ii) Ga-depleted front surface, [25,149,231,232] iii) Cu-depleted front surface, [121,149,196,233] iv) Cu-depleted front surface that facilitates Cd diffusion into the absorber (p-n buried heterojunction), [25,120,234] v) increased hole concentration, [149,235,236] vi) improved charge carrier lifetime, [149,218,235,237] vii) GB passivation, [196,238] and viii) decreased concentration of deep levels. [196,232] A series of record efficiency devices have been made possible using KF-PDTs, including 20.4% (Empa, 2013), [25] 20.8% (Zentrum für Sonnenenergieund Wasserstoff-Forschung Baden-Württemberg (ZSW), 2014), [71] 20.9% (SF, 2014), [73] 21.0% (Solibro, 2014), [239] 22.3% (SF, 2015), [240] and 20.8% (Empa, 2019).…”

Section: Potassiummentioning

confidence: 99%

Extrinsic Doping of Ink‐Based Cu(In,Ga)(S,Se)₂‐Absorbers for Photovoltaic Applications

Rokke

Drew

Alruqobah

et al. 2022

Advanced Energy Materials

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forest fires, and melting glaciers: it is evident that global over-reliance on fossil fuels must shift in favor of carbonfree energy sources to mitigate climate change. [1][2][3] Global energy consumption in 2020 was 162 Petawatt hours (PWh), out of which the electricity consumption was ≈30 PWh. [2,4] It is predicted that by 2050, an additional 30 TW will be required to meet mankind's increasing power demands. [5][6][7] The sun is an inexhaustible clean energy source transmitting nearly 120 000 TW to the earth's surface, far greater in magnitude than all other renewable energy sources combined. [8,9] While this power is abundantly available, harnessing it on terawatt scales with reliable and cost-efficient methods poses a tremendous challenge. [9] Photovoltaics (PVs) harvest the sun's energy by directly converting photons into electricity without the release of greenhouse gases (GHGs). PV systems are reliable, silent (no moving parts), and operate on a zero-cost energy source. These advantages coupled with the falling prices of energy storage systems suggest that PV systems can provide a continuous supply of electricity for residential and commercial applications. [8,9] The levelized cost of energy (LCOE) can be used to evaluate the cost-effectiveness of different energy sources. [10,11] For PV systems, LCOE denotes the discounted lifetime costs associated with the PV system installation divided by the discounted lifetime energy production of the system (typically ≈ 25 years). In sunny regions, the LCOE for utility-scale PV (29 $/MWh) now competes with electricity generated from conventional sources

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In Situ and Ex Situ Investigations of KF Postdeposition Treatment Effects on CIGS Solar Cells

Cited by 44 publications

References 21 publications

Surface and bulk effects of K in highly efficient Cu1-xKxInSe2 solar cells

Surface and bulk effects of K in highly efficient Cu1-xKxInSe2 solar cells

Fast C-V method to mitigate effects of deep levels in CIGS doping profiles

Extrinsic Doping of Ink‐Based Cu(In,Ga)(S,Se)₂‐Absorbers for Photovoltaic Applications

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In Situ and Ex Situ Investigations of KF Postdeposition Treatment Effects on CIGS Solar Cells

Cited by 44 publications

References 21 publications

Surface and bulk effects of K in highly efficient Cu1-xKxInSe2 solar cells

Surface and bulk effects of K in highly efficient Cu1-xKxInSe2 solar cells

Fast C-V method to mitigate effects of deep levels in CIGS doping profiles

Extrinsic Doping of Ink‐Based Cu(In,Ga)(S,Se)2‐Absorbers for Photovoltaic Applications

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Extrinsic Doping of Ink‐Based Cu(In,Ga)(S,Se)₂‐Absorbers for Photovoltaic Applications