D. Lincot et al. (Paris) Buffer Layers for Cu(In,Ga)(Se,S) 2 /BF/ZnO Solar Cells

Transcription

1 D. Lincot et al. (Paris) In 2 S 3 Buffer Layers for Cu(In,Ga)(Se,S) 2 /BF/ZnO Solar Cells 13 th European PVSEC (1995), p Absorber/surface - CIGS by evaporation (ZSW) β-in 2 S 3 by ALE (Atomic Layer Epitaxy) - indium acetylacetonate and hydrogen sulfide ( T = 150 C) - E g = 3.2 ev (vs. 2 ev known) ZnO bilayer by ALE using diethylzinc and water, n-doping by introducing additional pulses of trimethyl aluminum In 2 S 3 η [%] 13.5 N/A J sc [ma/cm 2 ] 30.6 N/A V oc [mv] 604 N/A FF [%] 73.0 N/A

2 F. Karg et al. (SSG) In 2 S 3 CIS-Module Development within the FORSOL Program: Structure and First Results 14 th European PVSEC (1997), p Absorber/surface - CIS by RTP (ZSW) β-in 2 S 3 by PVD (Pressure Vapor Deposition) ZnO In x S y η [%] 11.7 (-19.7%) 14.0 J sc [ma/cm 2 ] 34.6 (-9.2%) 37.8 V oc [mv] 498 (-4.4%) 520 FF [%] 68.3 (-4.5%) 71.4

3 D. Hariskos et al. (Stuttgart Uni.) In x (OH,S) y A Novel Cadmium Free Buffer Layer for Cu(In,Ga)Se 2 Based Solar Cells 1 24 th IEEE PVSC (1994), p. 91 (data) th European PVSEC (1995), p Absorber/surface - CIGS by thermal evaporation (Ga/(In+Ga) from 10 to 20%) In x (OH,S) y - the deposition takes place in an aqueous InCl 3 and thioacetamide (CH 3 CSNH 2 ) solution at temperatures up to 70 C - (see schematic) - XPS looks closer to In 2 S 3 pattern rather than In(OH) 3 pattern, though the pattern cannot merely be explained by the intermixture of those to phases ZnO In x (OH,S) y η [%] 14.9 (-2.0%) 15.2 J sc [ma/cm 2 ] 32.4 (-7.7%) 34.9 V oc [mv] 630 (+5.6%) 595 FF [%] 73.0 (0%) 73.0

4 Y. Tokita et al (Yamada, Konagai) (Tokio Institute of Technology) In x (OH,S) y High Efficiency Cu(InGa)Se 2 Thin-Film Solar Cells with Novel ZnIn x S y Buffer Layer 1 12 th Int. PVSEC (Jeju, Korea, 2001), p. 95 Absorber/surface - CIGS by 3 stage process in a Molecular Beam Epitaxy system - ZnCl 2 in the succeeding treatment most likely dopes surface with Zn In(OH) 3 :Zn 2+ (60 nm) - from ZnCl 2 (0.01M), InCl 3 4H 2 O (0.01M), and thiouria (0.15M) sln-s. - T s = 60 C - Measured R = 2.1x10 8 Ωcm - XRD showed pure In(OH) 3 In(OH) 3 :Zn 2+ η [%] 14.0 N/A J sc [ma/cm 2 ] 32.1 N/A V oc [mv] 575 N/A FF [%] 75.8 N/A

5 C. Kaufmann et al. (U of Oxford, ) In x (OH,S) y Growth Analysis of Chemical Bath Deposited In(OH) x S y Films as Buffer Layers for CuInS 2 Thin Film Solar Cells 1 28 th IEEE PVSC (2000), p. 688 Absorber/surface - CuInS 2 In(OH) x S y - InCl 3 (0.025M), CH 3 COOH (AcOH) (0.1M), CH 3 CSNH 2 (TA) (0.1M), water - 20 min, T = 70 C - fully deposited layer displays an indirect energy band gap at 2.2 ev, typical value for In 2 S 3 - As a conclusion we suggest, that In(OH) x S y growth initiates in a hydroxide /oxide phase and only after that incubation period, development of a sulphide phase continues rapidly. ZnO/ZnO:Al Ni/Al grids In(OH) x S y η [%] 9.1 N/A J sc [ma/cm 2 ] 21.5 N/A V oc [mv] 685 N/A FF [%] 61.8 N/A

6 C.H. Huang et al (U of Florida) In x (OH,S) y A Comparative Study of Chemical-bathdeposited, (Cd,Zn)S, ZnS, and In(OH) x S y Buffer Layer for CIS-based Solar Cells 28 th IEEE PVSC (2000), p. 696 Absorber/surface - CIGS & CIGSS by ISET & SSI In(OH) x S y by CBD ZnO bilayer by MOCVD ( µm) at 200 C (therefore, the finished cells might have the effect of annealing) In(OH) x S y η [%] 8.6 (-29.1%) 11.1 J sc [ma/cm 2 ] 27.3 (-15.0%) 31.4 V oc [mv] 525 (-1.0%) 530 FF [%] 59.7 (-11.1%) 66.3

7 K. Kushiya et al. (Showa Shell Sekiyu K.K.) Development of Cu(InGa)Se 2 Thin-Film Solar Cells with Zn-Compound Buffer ZnS 13 th European PVSEC, p (1995) CIGS/surface - CIGS by two-stage method (1-2 µm) CBD-ZnS (Zn compound) (< 30 nm) - Zn salts, S compounds and ammonia sln. to form a complex ion at the solution temperatures of 70 to 90 C - Anneal in air at 200 C for 15 min ZnO: Al by DC Magnetron sputtering at T s =200 C (1-2 µm) Ni/Al top metal grids by vacuum evaporation sulfur improved the p-n heterojunction quality between CIGS thin-film absorber and Zn-compound buffer. Zn(O,S,OH) η [%] 12.3 N/A J sc [ma/cm 2 ] 37.3 N/A V oc [mv] 493 N/A FF [%] 66.9 N/A

8 K. Kushiya et al. (Showa Shell Sekiyu K.K.) Formation of Robust Junction Between Cu(InGa)Se 2 -Based Absorber and Zn(O,S,OH) x Buffer Prepared on a 30cmx30cm Submodule ZnS 28 th IEEE PVSC, p. 424 (2000) Absorber/surface - CIGS CBD-Zn(O,S,OH) The FF depended on the bath transparency (%T) at 650 nm. Monitoring of the %T led to remarkable reduction of the deviation of FF. ZnO 30cm x 30cm substrate (860 cm 2 aperture area) Zn(O,S,OH) η [%] 12.5 N/A J sc [ma/cm 2 ] 32.7 N/A V oc [mv] V (587 mv/cell) N/A FF [%] 65.0 N/A

9 Tokio Nakada and Masayuki Mizutani (AGU, Japan) ZnS Improved Efficiency of Cu(In,Ga)Se 2 Thin Film Solar Cells with Chemically Deposited ZnS Buffer Layers by Air-Annealing -Formation of Homojunction by Solid Phase Diffusion- 28 th IEEE PVSC (2000), p.529 CIGS by 3-stage process using Molecular Beam Epitaxy (MBE) CBD-ZnS - from ZnSO 4 ( M)- ammonia (5-8M)- thiouria ( M) aqueous solution at 80 C (15 min in the bath) nm - really Zn(O,S,OH) though Eg = 3.8 ev Anneal in air at 200 C for 10 min It was evident that Zn was present inside of the CIGS layer at a position nm Furthermore, diffusion of S into the CIGS was found, suggesting the effect of surface passivation of the CIGS absorber layer. ZnO:Al MgF % cell has been reported CBD-ZnS η [%] 16.9 (+0.6%) 16.8 J sc [ma/cm 2 ] 35.2 (+4.5%) 33.6 V oc [mv] 647 (-3.3%) 668 FF [%] 74.3 (-0.8%) 74.9

10 Hans-J. Muffler et al. (Hahn Meitner s Institute, Germany) ZnS ILGAR Technology, VIII Sulfidic Buffer Layers for Cu(InGa)(S,Se) 2 Solar Cells Prepared by Ion Layer Gas Reaction (ILGAR) 28 th IEEE PVSC, p. 610 (2000) CIGS/surface - CIGSSe from SSG - Cleaned in deionized water or dimethylsulfoxide (DMSO) - CBD-Zn-Pretreatment: ZnCl 2 (40 mm), NH3 (5M), aqueous ammonia, DI-water a significant increase of open circuit voltage with increasing bath temperature is obtained. ILGAR-ZnS - 4 mm Zn(ClO 4 ) 2 is dissolved in acetonitride - 3 cycles are used with 5 sec sulfurization period at 125 C ZnCl 2 (solid) + H 2 S (gas) => ZnS (solid) + 2 HCl (gas) ILGAR - ZnS η [%] 14.2 (+0.7%) 14.1 J sc [ma/cm 2 ] 35.9 (+8.4%) 32.9 V oc [mv] 559 (-5.2%) 588 FF [%] 70.7 (-3.4%) 73.1

11 A.Ennaoui et al. (Hahn Meitner s Institute, Germany) ZnS Cd-Free Cu(Ga,In)(S,Se) 2 Thin Film Solar Cells and Mini-modules 16 th European PVSEC, p.682 (2000) CIGS/surface - CIGSS CBD-Zn(S,OH) - from ZnSO 4, NH 3, NH 2 NH 2 and SC(NH 2 ) 2 precursor - both NH 3, N 2 H 4 had to be present for the film to grow - best T = 70 C This self limiting process has the advantage to yield a good surface coverage at a minimum thickness. ZnO by MOCVD or DC-sputtering from ceramic targets (MOCVD had better efficiencies) Cells were interconnected monolithically. Zn(S,OH) η [%] 14.2 N/A J sc [ma/cm 2 ] 34.9 N/A V oc [mv] N/A FF [%] 71 N/A

12 C.H. Huang et al (U of Florida) A Comparative Study of Chemical-bathdeposited, (Cd,Zn)S, ZnS, and In(OH) x S y Buffer Layer for CIS-based Solar Cells ZnS 28 th IEEE PVSC (2000), p. 696 Absorber/surface - CIGS & CIGSS by ISET & SSI ZnS by CBD - ZnSO 4 (2.5x10-2 M), thiourea (3.5x10-2 M), NH 3 (1M), hydrazine (3M) - T varied between 70 and 80 C ZnO bilayer by MOCVD ( µm) at 200 C (therefore, the finished cells might have the effect of annealing) ZnS η [%] 9.8 (-13.3%) 11.1 J sc [ma/cm 2 ] 27.7 (-13.4%) 31.4 V oc [mv] 520 (-1.9%) 530 FF [%] 66.4 ( 0%) 66.3

13 R.A. Mickelsen et al. (Boeing) Large Area CuInSe 2 Thin-Film Solar Cells CdZnS 19 th IEEE PVSC (1987), p. 744 Absorber/surface - CIS by elemental co-evaporation Zn from and ZnS furnaces (evaporation) Al CdZnS η [%] 9.6 N/A J sc [ma/cm 2 ] 35.3 N/A V oc [mv] 432 N/A FF [%] 62.6 N/A

14 B. Dimmler et al. (U of Stuttgart) CdZnS Structure and Morphology of Evaporated Bilayer and selenized CuInSe 2 Films 20 th IEEE PVSC (1988), p Absorber/surface - CIS by evaporation of 2 layers CdZnS CdZnS η [%] N/A J sc [ma/cm 2 ] 30.2 N/A V oc [mv] 419 N/A FF [%] 66.4 N/A

15 K. Urabe et al. (Fuji Electric Corporate R&D, Ltd.) CdZnS Properties of CuInSe 2 Films for Solar Cell Applications 25 th IEEE PVSC (1996), p. 893 Absorber/surface - CIS and CIGS by simultaneous elemental evaporation µm Cu rich (T s =350 C for CIS, T s =450 C for CIGS) µm In rich (T s =450 C for CIS, T s =550 C for CIGS) and CdZnS by single-source EB evaporation CdZnS η [%] 10.5 N/A J sc [ma/cm 2 ] 37.8 N/A V oc [mv] 419 N/A FF [%] 66.4 N/A

16 C.H. Huang et al (U of Florida) CdZnS A Comparative Study of Chemical-bathdeposited, (Cd,Zn)S, ZnS, and In(OH) x S y Buffer Layer for CIS-based Solar Cells 28 th IEEE PVSC (2000), p. 696 Absorber/surface - CIGS & CIGSS by ISET & SSI (Cd,Zn)S by CBD - CdCl 2 (1.2x10-3 M), ZnCl 2 (6.27x10-4 M) thiourea (1.2x10-2 M), NH 3 (5.27x10-4 M), NH 4 Cl (1.39x10-3 M) - T varied between 70 and 80 C ZnO bilayer by MOCVD ( µm) at 200 C (therefore, the finished cells might have the effect of annealing) (Cd,Zn)S η [%] 9.5 (-16.8%) 11.1 J sc [ma/cm 2 ] 29.5 (-6.4%) 31.4 V oc [mv] 510 (-3.9%) 530 FF [%] 61.7 (-7.5%) 66.3

17 Review compiled by Alex Pudov, CSU, OCT 2002 superstrate T. Nakada et al. (AGU) Superstrate-Type Cu(In,Ga)Se2 Thin Film Solar Cells with ZnO Buffer Layer a Novel Approach to 10 % Efficiency 1 2nd World Conf. on PVSEC, p.413 Soda-lime glass ZnO:Al by DC magnetron Sputtering,2 µm, C, 2 Ω/sq CBD CdI2 (1.4x10 M), thiouria (.14 M), ammonia (1 M) aqueous sln. at C - Thickness = 300 nm Absorber / surface - CIS by 3-source co-evaporation method at 450 ºC substrate temperature - d (CIGS) µm Au contact -superstrate η [%] Jsc [ma/cm2] Voc [mv] FF [%] At high CIGS deposition temperatures, there is a strong intermixture of CIGS and ; at low T (300 C), the film does not grow as well

18 R.W. Birkmire et al. (IEC) superstrate Options for Fabrication and Design of CuInSe 2 Based Solar Cells 1 21 st IEEE PVSC (1990), p. 550 Soda-lime glass ITO C, 10 Ω/sq by evaporation, 1.0 µm Absorber / surface - CIS by 3-source thermal evaporation method at ºC substrate temperature 0.07 cm 2 Pt dot -superstrate η [%] 5.9 J sc [ma/cm 2 ] 34.6 V oc [mv] 330 FF [%] 53.0

19 Review compiled by Alex Pudov, CSU, OCT 2002 ZnO M. Bar et al. (Hahn Meitner s Institue, Germany) ILGAR-ZnO Window Extension Layer: An Adequate Substitution of the Conventional CBD- Buffer in Cu(In,Ga)(S,Se)2 based Solar Cells with Superior Device Performance (ILGAR Ion Layer Gas Reaction) Progress in Photovoltaics 2002, 10: (data Source) ; also 29th IEEE PVSC, 2002, to be publ. ;12th Int.-l PVSEC, 2001, p.489 Absorber / surface - CIGSSe - Cd2+ treatment in O4 + NH3 + H2O sln. for 10 min. at 80 C - rinsed in DI water ZnO WEL: - dipping in Zn(ClO4) : acetonitride (AN) - drying - exposing to NH3/H2O for 1 min at 155 C - repeat the above steps 25 times RF-sputtered i-zno / ZnO:Ga Ni / Al grids by thermal evaporation Thick ILGAR-ZnO/ Zn-rich CIGS; thin /CIGS; dashed Cd treated, buffer free; Dotted - untreated, buffer free ILGAR 14.6 (+ 3.4 %) η [%] Jsc 34.6 (+ 4.9 %) [ma/cm2] Voc [mv] 587 ( 0 %) FF [%] 72.1 (-1.4 %) g EC CIGS EF EV n+ - ZnO 400 nm WEL Cd diffused region

20 T. Minemoto (T. Negami) et al. (Ritsumeikan U., Japan) Highly Efficient Cd-Free Cu(In,Ga)Se 2 Solar Cells Using Novel Window Layer of (Zn,Mg)O Films ZnO 16 th European PVSEC, 2000, p.686 (data Source); also, 28 th IEEE PVSC, 2000, p.634 Absorber / surface - CIGS by Physical Vapor Deposition (2 µm) - Dipped in the Cd 2+ sln. to form p-n junction Zn(O,S) by Chemical Bath Deposition (thickness?) Zn 1-x Mg x O (x 0.06, Eg 3.38 ev) by RF cosputtering (0.1 µm) ITO (0.1 µm) *amount of O, S in Zn(O,S), thickness of it not specified in the papers **Mo was 0.8 µm Zn 1-x Mg x O / Zn(O,S) η [%] 16.2 (- 3.6 %) 16.8 J sc [ma/cm 2 ] 37.6 ( 0 %) similar V oc [mv] 632 ( 0 %) similar FF [%] 68.1 (- 4.1 %) 71 Approximate from a chart Normalized to cell parameters

21 K. Ramanathan et al. (NREL) Properties of Cd and Zn Partial Electrolyte Treated CIGS Solar Cells ZnO 1 29th IEEE PVSC, 2002, to be publ. (data source) 2 2 nd World Conf. on PVSEC p.477 (1998) 3 P. Johnson et al. 29 th IEEE PVSC, 2002, to be publ. Current Density (ma/cm2) ZnO Cd PE/ZnO Absorber / surface - CIGS (2-5 µm thick) - Dipped into Cd Partial Electrolyte for 22 min. at 80 C RF- sputtered i-zno ( nm) RF- sputtered ZnO:Al (200 nm) Ni / Al grid Internal QE (%) Voltage (V) Cd PE Cd PE 20 η [%] 15.7 (- 4.3 %) 16.4 J sc [ma/cm 2 ] 34.7 (+ 6.8 %) Wavelength (nm) 1000 V oc [mv] 636 (- 7.8 %) 690 FF [%] 72 (-1.9 %) 73.4

22 A. Yamada et al. (Tokyo Inst. Of Technolgy) Buried homojunction in Cu(InGa)Se2 Solar Cells Formed by Intentional Zn Doping ZnO 1 28 th IEEE PVSC, 2000, p S. Chaisitsak et al. 12 th Int-l PVSEC, 2001, p. 97 Absorber / surface - CIGS by Co-evaporation, grown in Molecular Beam Epitaxy system, using In-Ga-Se precursors on Mocoated Na-lime glass - Zn was evaporated onto the SIGS film (T s = 300 C) ZnO window bilayer by MOCVD (300 C) - n- ZnO 100 nm 10 1 Ω*cm - n + - ZnO:B 1500 nm 10 3 Ω*cm We did not grow any buffer layers Anneal at 200 C in air Zn doped η [%] 11.5 N/A J sc [ma/cm 2 ] 32.5 N/A V oc [mv] 540 N/A FF [%] 66.5 N/A A 14.6% efficient ZnO/i-ZnO/CIGS solar cell was achieved when ZnO was deposited by ALD.

23 L. Olson et al. (U. of Delaware) ZnO High Efficiency CIGS and CIS cells with CVD ZnO Buffer Layers 1 26th IEEE PVSC, 1997, p.363 (data source) 2 28th IEEE PVSC, 2000, p th IEEE PVSC, 1994, p.194 Absorber / surface - NREL CIGS - Degreased (rinsing) in TCA, acetone, methanol, DI water i-zno (MOCVD) is deposited by reacting Zn adduct with tetrahydrofuran (THF) Å at 250 ºC in H 2 atmosphere Å at 100 ºC later experiments showed that the following is sufficient: - treating substrate in N 2 at 250 ºC - ZnO growth at 100 ºC resistance of the layer >10 4 Ω*cm n ZnO TCO by RF- sputtering Ni / Al grid MOCVD ZnO η [%] 13.9 (- 9.1%) 15.3 J sc [ma/cm 2 ] 34.5 (+10.9 %) 31.1 V oc [mv] 581 ( %) 665 FF [%] 69.2 (-6.6 %) 74.1

24 J. Kessler et al. (U of Stuttgart) Interface Engineering Between CuInSe2 and ZnO ZnO a : CIS/ZnO/ZnO:Al : direct O 2 free b : CIS/(CBD)/ZnO(O 2 )/ZnO:Al : standard 1 23 th IEEE PVSC, 1993, p.447 Absorber / surface - CIS ZnO by RF (no O 2 atmosphere) ZnO:Al by RF Sputter damage to the CIS layer does not seem to be problematic No buffer η [%] 10.5 ( %) 12.4 J sc [ma/cm 2 ] 39.0 (+ 2.6 %) 38.0 V oc [mv] 398 ( %) 460 FF [%] 68 (- 4.2 %) 71.0 a : CIS/ZnO:Al : direct i free b : CIS/ZnO(O 2 )/ZnO:Al : standard c : CIS/ZnO/ZnO:Al : direct O 2 free a : CIS/(CBD)/ZnO(O 2 )/ZnO:Al : standard b : CIS/(CBD)/ZnO:Al : O 2 free

25 J. Sterner et al. (Uppsala U., Sweden) ZnO Atomic Layer Epitaxy Growth of ZnO Buffer Layers in Cu(In,Ga)Se 2 Solar Cells 1 2 nd World Conf. on PVSEC, p.1145 (data source) Absorber / surface - CIGS (20-30 % Ga, which translates to E g = 1.16 ev) ALE buffer : ZnO from diethylzinc (DEZ), H 2 O, O 2, and N 2 sources at 150 ºC. Sequence: DEZ - H 2 O - O 2 with N 2 purges R Ω*cm ZnO:Al by RF- sputtering Ni / Al grid ZnO η [%] 11.7 (- 3.3 %) 12.1 J sc [ma/cm 2 ] 32.6 (+1.2 %) 32.2 V oc [mv] 512 (- 2.7 %) 526 FF [%] 70 (-1.8 %) 71.3

26 T. Nakada et al. (AGU) Superstrate-Type Cu(In,Ga)Se 2 Thin Film Solar Cells with ZnO Buffer Layer a Novel Approach to 10 % Efficiency ZnO 1 2 nd World Conf. on PVSEC, p.413 Soda-lime glass ZnO:Al ZnO Absorber / surface - CIGS by co-evaporation method at 500 ºC substrate temperature - Na 2 S was co-evaporated at the initial stage of CIGS preparation in order to enhance the crystallinity of CIGS films and cell performance. d (CIGS) 0.5 µm the performance was maximized to the Na 2 S total content (62 mg) and to the Ga/In+Ga ratio (0.15) E g (CIGS) = 1.06 ev η [%] No buffer - superstrate 10.2 ( %) superstrate 6-8 (due to /CIGS intermixing) J sc [ma/cm 2 ] 37.6 N/A V oc [mv] 476 N/A FF [%] 57 N/A

27 D. Hariskos et al. (Stuttgart Uni.) Buffer Layers for Cu(In,Ga)(Se,S) 2 /BF/ZnO Solar Cells 13 th European PVSEC (1995), p SnO 2 SnO 2 Absorber/surface - CIGS by thermal evaporation (Ga/(In+Ga) from 10 to 20%) SnO 2 - the deposition takes place in an aqueous SnCl 4, HCl and urea (H 2 NCONH 2 ) solution at a temperature of 70 C Sn(O,S) 2 - urea was replaced by thioacetamide (CH 3 CSNH 2 ) (0.1M) and SnCl 4 by Sn(AcO) 4 (0.005M); (HCl 0.25M); (same T) - O/S in the film can be controlled - E g = 4.0 ± 0.1 ev ZnO CIS CIS Sn(O,S) 2 CIGS CIGS Sn(O,S) 2 η [%] 12.2 (-15.6%) 14.1 J sc [ma/cm 2 ] 31.8 (-5.7%) 33.6 V oc [mv] 567 (-1.4%) 575 FF [%] 68.0 (-7.4%) 73.0

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29 Y. Ohtake, A.Yamada et al. (Tokyo Inst. Of Technolgy) In 2 Se 3 High Efficiency Cu(InGa)Se 2 Thin-Film Solar Cells with Novel ZnIn x Se y Buffer Layer 1 2 nd World Conf. on PVSEC (1998), p th IEEE PVSC (1996), p. 793 Absorber/buffer were formed in one vacuum cycle by co-evaporation. CIGS (Ga/(Ga+In) near the surface was 30%) In x Se y (< 50 nm) - Se/Zn and Se/In ratios were 10 and 15, respectively Textured ZnO by MOCVD Al top grids by vacuum evaporation Anneal in air In x Se y η [%] 13.3 N/A J sc [ma/cm 2 ] 30.5 N/A V oc [mv] 600 N/A FF [%] 72.5 N/A

30 Se Han Kwon et al. (Korea Advanced Institute of Science and Technology) Growth of CuIn 3 Se 5 Layer on the CuInSe3 Film and its Effect on the Photovoltaic Properties of In 2 Se 3 /CuInSe 2 Solar Cells In 2 Se 3 26 th IEEE PVSC (1997), p. 395 Absorber/surface - CIS by three stage co-evaporation: - Co-evaporation of In-Se at T s = 300 C - Co-evaporation of Cu-Se at T s = 550 C - In-Se at T s = 550 C to form an In-rich surface In 2 Se 3 deposited at T s = 350 C w/o breaking the vacuum ZnO/ITO (1 µm) by RF sputtering In 2 Se 3 η [%] 8.5 N/A J sc [ma/cm 2 ] 35.1 N/A V oc [mv] 423 N/A FF [%] 57.0 N/A

31 T. Nakada et al. (AGU) In 2 Se 3 Superstrate-Type CuInSe2 Thin Film Solar Cells with Selenide Buffer Layers 25 th IEEE PVSC (1996), p. 893 Glass ZnO:Al (2 µm) by rf-magnetron sputtering (Ts = 540 C, R = 10 Ω/sq, T > 90%) In x Se y (0.? nm, T s = 350 C) by co-evaporation Absorber/surface - CIS - By co-evaporation with Na 2 Se - No photovoltaic performance was observed for the cells fabricated without or with too much Na 2 Se (these amounts of it produced bad CIS crystallinity) - T s between 300 and 400 C (350 best) Au back contacts In 2 Se 3 η [%] 5.1 N/A J sc [ma/cm 2 ] 28.9 N/A V oc [mv] 375 N/A FF [%] 47.0 N/A

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33 Y. Ohtake, A.Yamada et al. (Tokyo Inst. Of Technology) High Efficiency Cu(InGa)Se 2 Thin-Film Solar Cells with Novel ZnIn x Se y Buffer Layer ZnIn 2 Se nd World Conf. on PVSEC (1998), p th IEEE PVSC (1996), p. 793 Absorber/buffer were formed in one vacuum cycle by co-evaporation. CIGS (Ga/(Ga+In) near the surface was 30%) ZIS (ZnIn 2 Se 4 ) (50 nm) - Se/Zn and Se/In ratios were 10 and 15, respectively Textured ZnO by MOCVD Al top grids by vacuum evaporation Anneal in air ZIS (ZnIn 2 Se 4 ) η [%] 15.1 N/A J sc [ma/cm 2 ] 30.4 N/A V oc [mv] 652 N/A FF [%] 76.3 N/A

34 A. Delahoy et al. (EPV) ZnIn 2 Se 4 Ternary Source Materials for CIGS Buffer Layers 1 16 th European PVSEC (2000), p.767 Absorber/surface - CIGS ZIS by evaporation - they say it s somewhere between In 2 Se 3 :Zn and InSe:Zn - T S = 300 C? ZIS created better junction in terms of field for carrier collection η [%] 11.5 (-15.7%) 13.3 J sc [ma/cm 2 ] 32.1 (-6.2%) 34.1 V oc [mv] 560 (-1.6%) 569 FF [%] 64.3 (-5.1%) 68.1

35 W.Eisele et al. (Hahn Meitner s Inst., Ger.) XPS, TEM and NRA Investigations of the Cu(In,Ga)(S,Se) 2 /ZnSe Heterostructure for Highly Efficient Solar Cells ZnSe 1 12 th Int. PVSEC, Jeju, Korea, p.371 (2001) 2 28 th IEEE PVSC, p.692 (2000) ** Absorber/surface - CIGSS by Siemens Solar - Zn-treatment from ZnSO 4 metal precursor solution, NH 3, NH 2 NH 2, water - T = 70 C Zn(Se,OH) is deposited by adding to the Zntreatment solution the Se source - SeC(NH 2 ) 2 (the solution turns milky indicating the precipitation of ZnSe). To avoid the decomposition of selenourea in the aqueous solution, Na 2 SO 3 is added to the chalcogenide precursor solution. (20-50 nm) coverage, seems to be complete) before ZnSe there is a 5 nm Zn(OH) 2 *comes from 1 st reference ** comes from 2 nd reference ** Zn treatment **ZnSe w/o Zn treat-t η [%] J sc [ma/cm 2 ] V oc [mv] FF [%] ** ZnSe standard 14.5 ( 0%) 35.2 (+4.3%) 570 (-3.2%) 72.3 (-1.9%) *CBD- Reference

36 A.Ennaoui et al. (Hahn Meitner s Inst., Ger.) Cd-Free Cu(Ga,In)(S,Se) 2 Thin Film Solar Cells and Minimodules ZnSe 16 th European PVSEC, p.682 (2000) Absorber/surface - CIGSS CBD-Zn(Se,OH) - from ZnSO 4, NH 3, NH 2 NH 2 and SeC(NH 2 ) 2 precursor - both NH 3, N 2 H 4 had to be present for the film to grow - best T = 70 C This self limiting process has the advantage to yield a good surface coverage at a minimum thickness. ZnO by MOCVD or DC-sputtering from ceramic targets (CVD had better efficiencies) Cells were interconnected monolithically. ZnSe (cell) 14.2 η [%] (11.7 (-8.6%)) mini-m (12.7) mini-m J sc [ma/cm 2 ] 36.6 N/A V oc [mv] 570 N/A FF [%] 69 N/A

37 L.Olson, W.Addis, D.Huber (Washington State U.) Investigation of Polycrystalline Thin Film CuInSe 2 Solar Cells Based on ZnSe Windows 23 rd IEEE PVSC, p.603 (1003) Absorber/surface - CIS from Siemens Solar (2000 nm) - etched in KCN or Br ZnSe by MOCVD (20 nm) - Zn adduct reacted with H 2 Se n-zno by MOCVD (1000 nm) It should be noted that the device involved MOCVD growth of ZnO onto a ZnSe/CIS heterojunction at 350 C for one hour. Thus, it appears that the ZnSe/CIS interface can be very stable. Al/Ag grids MOCVD- ZnSe ZnSe η [%] 14.1 N/A J sc [ma/cm 2 ] 41.9 N/A V oc [mv] 506 N/A FF [%] 66.3 N/A

38 F.Engelhardt et al. (Oldenberg/SSG) ZnSe Interface Characterization of Cu(In,Ga)Se 2 Solar Cells Containing a New ZnSe Buffer Layer 2 nd World Conf. on PVSEC, p.1153 (1998) Absorber/surface - CIGS by Rapid Thermal Processing (RTR) of stacked elemental layers - Ga/Ga+In was about 15% - No Ga on the surface was observed ZnSe by Metal Organic Vapor Pressure Epitaxy (MOPVE) - T(growth) = 280 C ZnO by CVD Al grids ZnSe (10 nm) η [%] 11.6 ( 0%) 11.8 J sc [ma/cm 2 ] V oc [mv] FF [%]

39 Yasutoshi Ohtake et al. (Tokyo Inst. of Technology) Development of ZnO/ZnSe/CuIn 1-x Ga x Se 2 Thin-Film Solar Cells with Band Gap of 1.3 to 1.5 ev ZnSe 24 th IEEE PVSC, p.218 (1994) data source; also 13 th European PVSEC, p.2088 (1995) (In x Se y ) Absorber/surface - CIGS by a coevaporation method ( 2 µm) ZnSe by the ALD - in the same vacuum cycle - T = 250 C - < 50 nm Textured ZnO by MOCVD ( 2 µm) Al grids by vacuum evaporation ZnSe η [%] 11.6 N/A J sc [ma/cm 2 ] 35.2 N/A V oc [mv] 502 N/A FF [%] 65.4 N/A

40 K. Mitchel et al. (ARCO Solar, Inc.) ZnSe Single and Tandem Junction CuInSe 2 Cell and Module Technology 20 th IEEE PVSC, p (1988) ZnO/thin ZnSe/CIS Process? Thin ZnSe Thin η [%] 10.0 (-41%) 14.1 J sc [ma/cm 2 ] 40.1 (-2.2%) 41.0 V oc [mv] 391 (-29.9%) 508 FF [%] 64.1 (-5.6%) 67.7

41 A.Rumberg et al. ZnSe ZnSe Buffer Prepared by Iodine Enhanced Chemical Vapour Deposition for CIGSS Based Solar Cells 12 th Int. PVSEC, Jeju, Korea, p.89 (2001) Absorber/surface - CIGS ZnSe by iodine enhanced CVD - from ZnSe powder - source/substrate temperature 500/280 C microscope images of ZnSe buffers revealed an inhomogeneous and uncompleted coverage of these films lower carrier densities compared to devices were measured with C-V (higher depletion width) CVD- ZnSe η [%] 9.0% J sc [ma/cm 2 ] N/A N/A V oc [mv] N/A N/A FF [%] N/A N/A Voc and FF apparently were low

42 Acknowledgements: All the authors of the summarized articles are acknowledged. The review supported by the U.S. National Renewable Energy Lab. Acknowledgements For convenience, the list of the reviewed articles is following below. We appreciate comments and suggestions about the value and completeness of the review.

43 List of References: In2S3 D. Lincot et al. (Paris) Buffer Layers for Cu(In,Ga)(Se,S) 2 /BF/ZnO Solar Cells 13 th European PVSEC (1995), p F. Karg et al. (SSG) CIS-Module Development within the FORSOL Program: Structure and First Results 14 th European PVSEC (1997), p Inx(OH,S)y D. Hariskos et al. (Stuttgart Uni.) A Novel Cadmium Free Buffer Layer for Cu(In,Ga)Se 2 Based Solar Cells 1 24 th IEEE PVSC (1994), p. 91 (data) th European PVSEC (1995), p Y. Tokita et al (Yamada, Konagai) (Tokio Institute of Technology) High Efficiency Cu(InGa)Se 2 Thin-Film Solar Cells with Novel ZnIn x S y Buffer Layer 12 th Int. PVSEC (Jeju, Korea, 2001), p. 95 C. Kaufmann et al. (U of Oxford, ) Growth Analysis of Chemical Bath Deposited In(OH) x S y Films as Buffer Layers for CuInS 2 Thin Film Solar Cells 28 th IEEE PVSC (2000), p. 688 C.H. Huang et al (U of Florida) A Comparative Study of Chemical-bath-deposited, (Cd,Zn)S, ZnS, and In(OH) x S y Buffer Layer for CISbased Solar Cells 28 th IEEE PVSC (2000), p. 696 ZnS K. Kushiya et al. (Showa Shell Sekiyu K.K.) Development of Cu(InGa)Se 2 Thin-Film Solar Cells with Zn-Compound Buffer 13 th European PVSEC, p (1995) K. Kushiya et al. (Showa Shell Sekiyu K.K.)Formation of Robust Junction Between Cu(InGa)Se 2 -Based Absorber and Zn(O,S,OH) x Buffer Prepared on a 30cmx30cm Submodule 28 th IEEE PVSC, p. 424 (2000) Tokio Nakada and Masayuki Mizutani (AGU, Japan) Improved Efficiency of Cu(In,Ga)Se 2 Thin Film Solar Cells with Chemically Deposited ZnS Buffer Layers by Air-Annealing -Formation of Homojunction by Solid Phase Diffusion- 28 th IEEE PVSC (2000), p.529 Hans-J. Muffler et al. (Hahn Meitner s Institute, Germany) ILGAR Technology, VIII Sulfidic Buffer Layers for Cu(InGa)(S,Se) 2 Solar Cells Prepared by Ion Layer Gas Reaction (ILGAR) 28 th IEEE PVSC, p. 610 (2000)

44 A.Ennaoui et al. (Hahn Meitner s Institute, Germany) Cd-Free Cu(Ga,In)(S,Se) 2 Thin Film Solar Cells and Mini-modules 16 th European PVSEC, p.682 (2000) C.H. Huang et al (U of Florida) A Comparative Study of Chemical-bath-deposited, (Cd,Zn)S, ZnS, and In(OH) x S y Buffer Layer for CISbased Solar Cells 28 th IEEE PVSC (2000), p. 696 CdZnS R.A. Mickelsen et al. (Boeing) Large Area CuInSe 2 Thin-Film Solar Cells 19 th IEEE PVSC (1987), p. 744 B. Dimmler et al. (U of Stuttgart) Structure and Morphology of Evaporated Bilayer and selenized CuInSe 2 Films 20 th IEEE PVSC (1988), p K. Urabe et al. (Fuji Electric Corporate R&D, Ltd.) Properties of CuInSe 2 Films for Solar Cell Applications 25 th IEEE PVSC (1996), p. 893 C.H. Huang et al (U of Florida) A Comparative Study of Chemical-bath-deposited, (Cd,Zn)S, ZnS, and In(OH) x S y Buffer Layer for CISbased Solar Cells 28 th IEEE PVSC (2000), p. 696 superstrate T. Nakada et al. (AGU) Superstrate-Type Cu(In,Ga)Se 2 Thin Film Solar Cells with ZnO Buffer Layer a Novel Approach to 10 % Efficiency 2 nd World Conf. on PVSEC, p.413 R.W. Birkmire et al. (IEC) Options for Fabrication and Design of CuInSe 2 Based Solar Cells 21 st IEEE PVSC (1990), p. 550 ZnO M. Bar et al. (Hahn Meitner s Institue, Germany) ILGAR-ZnO Window Extension Layer: An Adequate Substitution of the Conventional CBD- Buffer in Cu(In,Ga)(S,Se) 2 based Solar Cells with Superior Device Performance, Progress in Photovoltaics 2002, 10: (data Source); 29 th IEEE PVSC, 2002, to be publ. ;12 th Int.-l PVSEC, 2001, p.489 T. Minemoto (T. Negami) et al. (Ritsumeikan U., Japan) Highly Efficient Cd-Free Cu(In,Ga)Se 2 Solar Cells Using Novel Window Layer of (Zn,Mg)O Films 16 th European PVSEC, 2000, p.686 (data Source); also, 28 th IEEE PVSC, 2000, p.634 K. Ramanathan et al. (NREL) Properties of Cd and Zn Partial Electrolyte Treated CIGS Solar Cells 1 29 th IEEE PVSC, 2002, to be publ. (data source) 2 nd 2 World Conf. on PVSEC p.477

45 3 P. Johnson et al. 29 th IEEE PVSC, 2002, to be publ. A. Yamada et al. (Tokyo Inst. Of Technolgy) Buried homojunction in Cu(InGa)Se 2 Solar Cells Formed by Intentional Zn Doping 1 28 th IEEE PVSC, 2000, p.462; 2 S. Chaisitsak et al. 12 th Int-l PVSEC, 2001, p. 97 L. Olson et al. (U. of Delaware) High Efficiency CIGS and CIS cells with CVD ZnO Buffer Layers 1 26 th IEEE PVSC, 1997, p.363 (data source) 2 28 th IEEE PVSC, 2000, p th IEEE PVSC, 1994, p.194 J. Kessler et al. (U of Stuttgart) Interface Engineering Between CuInSe 2 and ZnO 23 th IEEE PVSC, 1993, p.447 J. Sterner et al. (Uppsala U., Sweden) Atomic Layer Epitaxy Growth of ZnO Buffer Layers in Cu(In,Ga)Se 2 Solar Cells 2 nd World Conf. on PVSEC, p.1145 (data source) T. Nakada et al. (AGU) Superstrate-Type Cu(In,Ga)Se 2 Thin Film Solar Cells with ZnO Buffer Layer a Novel Approach to 10 % Efficiency 2 nd World Conf. on PVSEC, p.413 SnO2 D. Hariskos et al. (Stuttgart Uni.) Buffer Layers for Cu(In,Ga)(Se,S) 2 /BF/ZnO Solar Cells 13 th European PVSEC (1995), p In2Se3 Y. Ohtake, A.Yamada et al. (Tokyo Inst. Of Technolgy) High Efficiency Cu(InGa)Se 2 Thin-Film Solar Cells with Novel ZnIn x Se y Buffer Layer 1 2 nd World Conf. on PVSEC (1998), p th IEEE PVSC (1996), p. 793 Se Han Kwon et al. (Korea Advanced Institute of Science and Technology) Growth of CuIn 3 Se 5 Layer on the CuInSe 2 Film and its Effect on the Photovoltaic Properties of In 2 Se 3 /CuInSe 2 Solar Cells 26 th IEEE PVSC (1997), p. 395 T. Nakada et al. (AGU) Superstrate-Type CuInSe 2 Thin Film Solar Cells with Selenide Buffer Layers 25 th IEEE PVSC (1996), p. 893 ZIS A. Delahoy et al. (EPV) Ternary Source Materials for CIGS Buffer Layers 16 th European PVSEC (2000), p.767 Y. Ohtake, A.Yamada et al. (Tokyo Inst. Of Technolgy) High Efficiency Cu(InGa)Se 2 Thin-Film Solar Cells with Novel ZnInxSey Buffer Layer 1 2 nd World Conf. on PVSEC (1998), p th IEEE PVSC (1996), p. 793

46 ZnSe W.Eisele et al. (Hahn Meitner s Inst., Ger.) XPS, TEM and NRA Investigations of the Cu(In,Ga)(S,Se) 2 /ZnSe Heterostructure for Highly Efficient Solar Cells 1 12 th Int. PVSEC, Jeju, Korea, p.371 (2001); 2 28 th IEEE PVSC, p.692 (2000) A.Ennaoui et al. (Hahn Meitner s Inst., Ger.) Cd-Free Cu(Ga,In)(S,Se) 2 Thin Film Solar Cells and Mini-modules 16 th European PVSEC, p.682 (2000) L.Olson, W.Addis, D.Huber (Washington State U.) Investigation of Polycrystalline Thin Film CuInSe 2 Solar Cells Based on ZnSe Windows 23 rd IEEE PVSC, p.603 (1003) F.Engelhardt et al. Interface Characterization of Cu(In,Ga)Se 2 Solar Cells Containing a New ZnSe Buffer Layer 2 nd World Conf. on PVSEC, p.1153 (1998) Yasutoshi Ohtake et al. (Tokyo Inst. of Technology) Development of ZnO/ZnSe/CuIn 1-x Ga x Se 2 Thin-Film Solar Cells with Band Gap of 1.3 to 1.5 ev 24 th IEEE PVSC, p.218 (1994) data source; also 13 th European PVSEC, p.2088 (1995) (In x Se y ) K. Mitchel et al. (ARCO Solar, Inc.) Single and Tandem Junction CuInSe 2 Cell and Module Technology 20 th IEEE PVSC, p (1988) A.Rumberg et al. ZnSe Buffer Prepared by Iodine Enhanced Chemical Vapour Deposition for CIGSS Based Solar Cells 12 th Int. PVSEC, Jeju, Korea, p.89 (2001)