First Solar, Inc.

Patent Trials and Appeals Board

Jul 20, 2021

2021002627 (P.T.A.B. Jul. 20, 2021)

UNITED STATES PATENT AND TRADEMARK OFFICE
UNITED STATES DEPARTMENT OF COMMERCE
United States Patent and Trademark Office
Address: COMMISSIONER FOR PATENTS
P.O. Box 1450
Alexandria, Virginia 22313-1450
www.uspto.gov
APPLICATION NO. FILING DATE FIRST NAMED INVENTOR ATTORNEY DOCKET NO. CONFIRMATION NO.
16/305,455 11/29/2018 Kenneth Ring 57721-US-PCT 4091
109944 7590 07/20/2021
MacMillan, Sobanski and Todd, LLC - FIRST SOLAR
One Maritime Plaza, 5th Floor
720 Water St.
Toledo, OH 43604
EXAMINER
SMITH, ERIC R
ART UNIT PAPER NUMBER
1726
NOTIFICATION DATE DELIVERY MODE
07/20/2021 ELECTRONIC
Please find below and/or attached an Office communication concerning this application or proceeding.
The time period for reply, if any, is set in the attached communication.
Notice of the Office communication was sent electronically on above-indicated "Notification Date" to the
following e-mail address(es):
MST@mstfirm.com
PTOL-90A (Rev. 04/07)

UNITED STATES PATENT AND TRADEMARK OFFICE
____________

BEFORE THE PATENT TRIAL AND APPEAL BOARD
____________

Ex parte KENNETH RING, WILLIAM H. HUBER,
HONGYING PENG, MARKUS GLOECKLER,
GOPAL MOR, FENG LIAO,
ZHIBO ZHAO, and ANDREI LOS

Appeal 2021-002627
Application 16/305,455
Technology Center 1700
____________

Before JEFFREY B. ROBERTSON, DONNA. M. PRAISS, and
JANE E. INGLESE, Administrative Patent Judges.

PRAISS, Administrative Patent Judge.

DECISION ON APPEAL1

1 In this Decision, we refer to the Specification filed Nov. 29, 2018
(“Spec.”), the Final Office Action dated May 4, 2020 (“Final Act.”), the
Appeal Brief filed Oct. 2, 2020 (“Appeal Br.”), the Examiner’s Answer
dated Jan. 15, 2021 (“Ans.”), and the Reply Brief filed Mar. 8, 2021 (“Reply
Br.).
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Application 16/305,455

2
Pursuant to 35 U.S.C. § 134(a), Appellant2 appeals from the
Examiner’s decision to reject claims 1–9. We have jurisdiction under
35 U.S.C. § 6(b).
We AFFIRM.

STATEMENT OF THE CASE
The invention relates to photovoltaic devices. Spec. ¶ 1. According to
the Specification, photovoltaic devices typically include a front contact, a
back contact, and a plurality of semiconductor layers disposed on a
transparent substrate. Id. ¶ 2. The Specification describes an absorber layer
formed between the front contact and the back contact comprising cadmium,
selenium, and tellurium wherein the absorber layer is doped with copper and
silver via any known method. Id. ¶¶ 25, 26. The Specification states that “it
was surprisingly found that less [silver] dopant is required [c]ompared to the
levels of [copper] dopant.” Id. ¶ 50. Independent claim 1, reproduced below,
is illustrative of the subject matter on appeal (emphasis added).
1. A photovoltaic device comprising:
an absorber layer that converts photon energy to
electrical current, wherein:
the absorber layer comprises a II-VI semiconductor
material comprising cadmium, selenium, and tellurium; and
the absorber layer is doped with copper and silver at a
ratio of copper to silver greater than 2:1.
Appeal Br. 9 (Claims Appendix).

2 We use the word “Appellant” to refer to “applicant” as defined in
37 C.F.R. § 1.42. Appellant identifies First Solar, Inc. as the real party in
interest. Appeal Br. 3.
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ANALYSIS
We review the appealed rejections for error based upon the issues
Appellant identifies, and in light of the arguments and evidence produced
thereon. Ex parte Frye, 94 USPQ2d 1072, 1075 (BPAI 2010) (precedential)
(cited with approval in In re Jung, 637 F.3d 1356, 1365 (Fed. Cir. 2011)
(“[I]t has long been the Board’s practice to require an applicant to identify
the alleged error in the examiner’s rejections.”)). After considering the
argued claims in light of each of Appellant’s arguments, we are not
persuaded Appellant has identified reversible error in the appealed rejection.
The Examiner rejects claims 1 and 2 under 35 U.S.C. § 103 as
unpatentable over Cheng (WO 2014/165225 A1, published Oct. 9, 2014) in
combination with Blaydes (US 2014/0326315 A1, published Nov. 6, 2014)
for the reasons provided in the Final Office Action. Final Act. 2–3. The
Examiner rejects claims 3–9 under 35 U.S.C. § 103 over Cheng and Blaydes
in combination with additional secondary references.3 Final Act. 3–6.
Appellant only presents arguments with respect to the rejection of claims 1
and 2. Appeal Br. 3, 8. Accordingly, we summarily affirm the rejections of
claims 3–9.
We address Appellant’s arguments below.
Independent Claim 1
The Examiner finds that Cheng discloses a photovoltaic device
comprising an absorber layer comprising cadmium and tellurium that is

3 Zhong (US 2010/0055826 A1, pub. Mar. 4, 2010); Chin (US
2012/0042950 A1, pub. Feb. 23, 2012); and Compaan (US 2013/0174895
A1, pub. July 11, 2013).
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doped with copper and silver. Final Act. 2. The Examiner acknowledges that
Cheng does not specifically teach the absorber layer comprises selenium or a
particular ratio of copper to silver. Id. at 3. The Examiner finds a person
having ordinary skill in the art would have modified Cheng with Blaydes’
teaching to include selenium with cadmium and tellurium in an absorber
layer for the purpose of minimizing the thickness of the window layer,
improving the passivation of grain boundaries, and increasing efficiency. Id.
(citing Blaydes ¶¶ 36–39, 48). The Examiner determines it would have been
obvious to a person having ordinary skill in the art to vary the amount of
copper and silver in the absorber layer to achieve the desired stability of a
back contact. Id. (citing Chen 9:15–10:3).
According to Appellant, the Examiner erred by failing to explain (1)
how varying the ratio of copper to silver would result in the claimed ratio
and (2) why a person of ordinary skill in the art would have had a reasonable
expectation of success to formulate the claimed absorber doped with copper
and silver at a copper to silver ratio greater than 2:1 as required by claim 1.
Appeal Br. 5. Appellant asserts even if the Examiner established prima facie
obviousness, unexpected results based on the claimed ratios of copper to
silver is sufficient to rebut obviousness. Id. at 6. According to Appellant,
examples in Appellant’s Specification test different ratios of copper to silver
and the Specification’s paragraph 57 indicates that the literature suggests the
equivalency, not superiority, of silver in place of copper as a dopant in
cadmium tellurium absorber solar cells. Id. at 7. Appellant also argues that
because Chen does not specify a ratio of copper to silver, Chen’s disclosure
is “too broad.” Id. at 8.

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Appellant’s arguments do not persuade us that the Examiner
reversibly erred in rejecting claim 1 as obvious over Cheng and Blaydes.
The preponderance of the evidence in this Appeal record supports the
Examiner’s determination that, in view of the cited prior art references, it
would have been obvious for a person having ordinary skill in the art to use
any proportion of copper to silver and vary the ratio through the course of
routine optimization. Ans. 8. Appellant asserts that silver and copper were
expected to function equally well as a dopant in cadmium tellurium absorber
solar cells. Appeal Br. 7 (citing Spec. ¶ 57). Therefore a person having
ordinary skill in the art would have had a reasonable expectation of success
using any ratio of copper to silver as a dopant, including a greater proportion
of copper compared to silver as claimed. Appellant acknowledges that the
“too broad” scope of Chen’s disclosure is not “finite” with respect to the
proportion of copper to silver and, thus, encompasses the claimed
proportion. Id. at 8. Accordingly, Appellant’s argument that the Examiner
failed to set forth a prima facie case of obviousness of claim 1 over the
combination of Cheng and Blaydes is not supported by the record.
Turning to Appellant’s objective evidence comparing silver and
copper as dopants, Appellant represents that literature “suggests the
equivalency––not superiority––of Ag in place of Cu as a dopant.” Spec.
¶ 56; Appeal Br. 6–7. Appellant does not direct us to any particular aspect or
scale on which the purported expected “equivalency” was measured or
understood in the prior art. That silver and copper both function as dopants
in absorber solar cells is not disputed and their use separately or together is
taught by Cheng. Cheng 12:24–25. Appellant’s Specification compares the
performance of silver and copper as dopants and reports the initial efficiency
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of silver devices was about 6% higher than comparative copper-doped
devices and, after an accelerated stress test, the copper devices showed an
efficiency deterioration of more than 15% while the silver-doped devices
showed a deterioration of about 8%. Spec. ¶ 59. According to the
Specification’s paragraph 56, that silver outperforms copper as a dopant “is
somewhat unexpected considering that the electron shell configurations are
very similar.” Id. ¶ 56 (emphasis added).
Appellant has not established that the outer limits of its claimed range
of “greater than 2:1” provide unexpected results compared to the prior art
range because Appellant has not compared the claimed compositions to the
closest prior art, which is Cheng. The burden of establishing that unexpected
results support a conclusion of nonobviousness rests with Appellant. In re
Huang, 100 F.3d 135, 139 (Fed. Cir. 1996). “[W]hen unexpected results are
used as evidence of nonobviousness, the results must be shown to be
unexpected compared with the closest prior art.” In re Baxter Travenol
Labs., 952 F.2d 388, 392 (Fed. Cir. 1991). “[I]t is not enough to show that
results are obtained which differ from those obtained in the prior art: that
difference must be shown to be an unexpected difference.” See In re Klosak,
455 F.2d 1077, 1080 (CCPA 1972) (emphasis in original). Additionally, the
relied-upon results must be commensurate in scope with the claims. See In
re Peterson, 315 F.3d 1325, 1329–31 (Fed. Cir. 2003). “Establishing that
one (or a small number of) species gives unexpected results is inadequate
proof, for ‘it is the view of [the CCPA] that objective evidence of non-
obviousness must be commensurate in scope with the claims which the
evidence is offered to support.’” See In re Greenfield, 571 F.2d 1185, 1189
(CCPA 1978) (quoting In re Tiffin, 448 F.2d 791, 792 (CCPA 1971)).
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Finally, “it is well settled that unexpected results must be established by
factual evidence. ‘Mere argument or conclusory statements in the
specification does not suffice.’” See In re Geisler, 116 F.3d 1465, 1470 (Fed.
Cir. 1997) (quoting In re De Blauwe, 736 F.2d 699, 705 (Fed. Cir. 1994));
see also In re Pearson, 494 F.2d 1399, 1405 (CCPA 1974) (“Attorney’s
argument in a brief cannot take the place of evidence.”).
At most, Appellant’s objective evidence shows that silver “somewhat
unexpected[ly]” performs better than copper as a dopant. How this
difference between the two known dopants translates into unexpected results
over the recited “greater than 2:1” range is not sufficiently explained or
supported by Appellant. Given the breadth of the range claimed, we agree
with the Examiner that Appellant’s data is neither commensurate with the
scope of the claim nor compared to the closest prior art, which is Cheng’s
disclosure of using copper and/or silver as dopants. Ans. 10 (“A skilled
artisan would reasonably expect the properties of an absorber layer with an
extremely small amount of silver as compared to copper to have similar
properties to an absorber layer with only copper.”). Accordingly, we do not
find Appellant’s objective evidence of non-obviousness of the claimed
“greater than 2:1” ratio of copper to silver to be adequate, in light of all of
the evidence of record, to support a reversal of the obviousness rejection.
In sum, Appellant’s arguments are not persuasive of error in the
Examiner’s conclusion of obviousness. Accordingly, we affirm the
Examiner’s rejection of claim 1 under 35 U.S.C. § 103 over Cheng and
Blaydes.

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Dependent Claim 2
Claim 2 depends from claim 1 and recites “wherein the ratio of copper
to silver is between 5:1 and 40:1.” Appeal Br. 9 (Claims Appendix).
Appellant argues that the Examiner’s rejection should be reversed
because the finding that the ratio of copper to silver would also necessarily
be varied by a person having ordinary skill in the art is not a limitation
recited by the claim. Appeal Br. 6.
Appellant’s arguments are not persuasive of error. As discussed above
in connection with claim 1, the Examiner has set forth a prima facie case of
obviousness over the combination of Cheng and Blaydes. Appellant relies on
the same objective evidence of non-obviousness for both claims 1 and 2.
Appeal Br. 6–7. Appellant’s objective evidence shows that silver “somewhat
unexpected[ly]” performs better than copper as a dopant. How this
difference between the two known dopants translates into unexpected results
compared to the recited “between 5:1 and 40:1” range is not adequately
explained or supported by Appellant. Given the breadth of the range
claimed, we agree with the Examiner that Appellant’s data is neither
commensurate with the scope of the claim nor compared to the closest prior
art which is Cheng’s disclosure of using copper and/or silver as dopants.
Ans. 10. As the Examiner points out, only one data point (13:1) falls within
claim 2’s recited range, which is insufficient to establish the criticality of the
narrower range. Id.
Accordingly, we do not find Appellant’s objective evidence of non-
obviousness of the claimed “between 5:1 and 40:1” ratio of copper to silver
to be adequate, in light of all of the evidence of record, to support a reversal
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of the obviousness rejection of claim 2 under 35 U.S.C. § 103 over Cheng
and Blaydes.
Additional Argument in Reply Brief
Finally, we observe that Appellant’s Reply Brief presents an argument
not previously presented in the Appeal Brief regarding the Examiner’s
obviousness rejection over Cheng and Blaydes (Reply Br. 4–5; “Cheng
repeatedly discloses that the use of a metal oxide to form ohmic back
contacts relates to device stability . . . . Cheng never states, as alleged by the
Examiner, that the relative amounts of copper and silver in the absorber
layer effects the stability of the back contact.”). This argument was not
presented in the Appeal Brief, and Appellant has not proffered a showing of
good cause explaining why the argument could not have been presented in
the Appeal Brief. Appellant’s citation to page 5 of the Answer is the portion
of the Answer that restates the rejection from the Final Action. Compare
Ans. 5 with Final Act. 3. Therefore, we will not consider this new and
untimely argument in our assessment of the Examiner's § 103 rejection. 37
C.F.R. § 41.37, § 41.41. Even if we were to consider Appellant’s untimely
argument, the record supports the Examiner’s finding because Cheng
discloses both “[t]he controlled doping and novel ohmic contact are
incorporated to form CdTe solar cells with improved stability.” Chang 9:28–
29 (emphasis added). Thus, contrary to Appellant’s argument, Cheng does
attribute improved stability to the copper and/or silver doping.

CONCLUSION
For these reasons and those provided in the Final Office Action and
the Examiner’s Answer, we uphold the Examiner’s rejections of claims 1–9.
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No time period for taking any subsequent action in connection with
this appeal may be extended under 37 C.F.R. § 1.136(a)(1)(iv).
In summary:
Claim(s)
Rejected 35 U.S.C. § Reference(s)/Basis Affirmed Reversed
1, 2 103 Cheng, Blaydes 1, 2
3, 4 103 Cheng, Blaydes, Chin 3, 4
5, 7–9 103 Cheng, Blaydes, Compaan 5, 7–9
6 103 Cheng, Blaydes, Zhong 6
Overall
Outcome 1–9

AFFIRMED