Ex Parte Varghese et al

Patent Trial and Appeal Board

Apr 29, 2016

12218558 (P.T.A.B. Apr. 29, 2016)

UNITED STA TES p A TENT AND TRADEMARK OFFICE
APPLICATION NO. FILING DATE
12/218,558 07/16/2008
128940 7590 04/29/2016
SolAero Technologies Corp,
10420 Research Road SE
Albuquerque, NM 87123
FIRST NAMED INVENTOR
Tansen Varghese
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
ATTORNEY DOCKET NO. CONFIRMATION NO.
7009 (9456-106293) 3548
EXAMINER
CHERN, CHRISTINA
ART UNIT PAPER NUMBER
1755
MAILDATE DELIVERY MODE
04/29/2016 PAPER
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.
PTOL-90A (Rev. 04/07)
UNITED STATES PATENT AND TRADEMARK OFFICE
BEFORE THE PATENT TRIAL AND APPEAL BOARD
Ex parte TANSEN VARGHESE, MARK A. STAN, ARTHUR
CORNFELD, FRED NEWMAN, and ALLEN A. GRA Y 1
Appeal2014-004860
Application 12/218,558
Technology Center 1700
Before PETER F. KRATZ, BEYERL Y A. FRANKLIN and
MICHAEL P. COLAIANNI, and, Administrative Patent Judges.
COLAIANNI, Administrative Patent Judge.
DECISION ON APPEAL
1 Appellants identify the real party in interest as "Emcore Solar Power, Inc."
(Appeal Brief filed November 20, 2013 ("App. Br.") 1).
Appeal2014-004860
Application 12/218,558
Appellants appeal under 35 U.S.C. § 134 the final rejection of claims
1, 3, 5-16, 18-21 24--28, and 50. We have jurisdiction over the appeal
pursuant to 35 U.S.C. § 6(b).
We AFFIRM.
Appellants' invention relates to solar cell semiconductor devices,
particularly, inverted metamorphic multijunction solar cells. (Spec. 4, 11. 1-
4).
Claims 1, 21 and 50 are the independent claims. Claim 1 is
representative (emphasis added.)
1. A method of forming a multijunction solar cell
comprising an upper subcell, a middle subcell, and a lower
subcell, the method comprising:
providing a first substrate for the epitaxial growth of
semiconductor material;
forming an upper first solar subcell on said first substrate
having a first band gap;
forming a middle second solar subcell over said first
solar subcell having a second band gap smaller than said first
band gap;
forming a graded interlayer over said second solar
subcell, the graded interlayer having a third band gap greater
than said second band gap;
forming a lower third solar subcell over said graded
interlayer having a fourth band gap smaller than said second
band gap such that said third subcell is lattice mismatched with
respect to said second subcell;
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Application 12/218,558
forming a contact layer having a band gap greater than
said second band gap over said third subcell; and
depositing an ohmic metal contact layer over said contact
layer to act as a mirror for reflecting any light reaching the
ohmic metal contact layer back to the adjacent third subcell.
(Claims App'x of App. Br. C-1.)
Appellants appeal the following rejections to the appealed claims.2
I. Claims 1, 3, 5-11, 15, 16, and 50 as unpatentable under
35 U.S.C. § 103(a) over Wanlass. 3 (Final Rejection dated
September 6, 2013 ("Final Rej.") 3-9).
II. Claims 12-14, 21, and 24--28 as unpatentable under 35 U.S.C.
§ 103(a) over Wanlass in view of King4 (Final Rej. 9-11 and 13-19).
III. Claims 18-'20 as unpatentable under 35 U.S.C. § 103(a) over
Wanlass in view of Iles5 (Final Rej. 12-13).
IV. Claims 1, 3, 5-16, 18-21, 24--28, and 50 as provisionally rejected
on the ground of nonstatutory obviousness double patenting as
unpatentable over claims 15-21 and 23 of co-pending application U.S.
11/860,183 in view of Wanlass (Final Rej. 20-22).
2 A 35 U.S.C. § 102 rejection over Wanlass has been withdrawn by the
Examiner. (Examiner's Answer dated January 2, 2014 ("Ans.") 2.)
3 U.S. 2006/0144435 Al to Wanlass, published July 6, 2006.
4 U.S. 2005/0274411 Al to King et al., published December 15, 2005.
5 U.S. 2004/0166681 Al to Iles et al., published August 26, 2004.
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Application 12/218,558
V. Claims 1, 3, 5-16, 18-21, 24--28, and 50 as provisionally rejected
on the ground of nonstatutory obviousness double patenting as
unpatentable over claims of co-pending application U.S. 11/860,142
in view of Wanlass (Final Rej. 22-24). However, this rejection has
been rendered moot in view of the abandoning of the co-pending
application on December 4, 2013.
With regard to rejections (I) to (III), Appellants focus their arguments on
independent claim 1 (App. Br. 5-12). Rejection (II) includes independent
claim 21, but Appellants merely rely on arguments made regarding claim 1
with the additional statement that King does not cure any alleged deficiency
with Wanlass (App. Br. 12). Any claims not argued separately with regard
to Rejections (I-III) will stand or fall with our analysis regarding the present
independent claim 1.
FINDINGS OF FACT & ANALYSIS
REJECTION (I): Claims 1, 3, 5-11, 15, 16, and 50.
The Examiner finds that Wanlass discloses all the limitations of claim
1, except for the contact layer having a band gap greater than that of the first
or second subcell and the contact layer composed of InGaAlAsas recited in
claims 3 and 66 (Final Rej. 3--4). The Examiner finds, however, that
6 Our discussion of dependent claims 3 and 6 is for purposes of background
in considering the Examiner's findings and obviousness position with
respect to representative claim 1 and consideration of Appellants' arguments
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Application 12/218,558
Wanlass teaches adding aluminum to raise the band gap of Groups II-V
ternary and quaternary alloys without changing the lattice constant (Final
Rej. 4, Wanlass, i-f38). The Examiner additionally finds Wanlass disclosing
depositing a back surface reflector over the contact layer and that the band
gap of a grading layer (non-active semiconductor layer) should be higher
than that of a subcell (active semiconductor layer) in a "preceding layer" so
that the grading layer is transparent to any solar radiation not absorbed by
the subcell and thus incident radiation will not be thermalized and lost as
heat energy (Final Rej. 4; Ans. 3--4; Wanlass, i-fi-134 and 39).
The Examiner concludes that, in accordance with Wanlass' own
teachings, it would have been obvious to modify Wanlass' contact layer by
including aluminum to form an InGaAlAs contact layer having a band gap
greater than the subcells, wherein the contact layer would be transparent to
solar radiation not absorbed by the subcells thereby reducing the amount of
heat and energy lost to the contact layer, which provides for an enhanced
reflection effect by the back surface reflector of the solar radiation to the
solar subcells and an overall more efficient device (Final Rej. 4; Ans. 3-5
and 7-8).
The Examiner further finds that the band gap of the subcells and
contact layer can be modified in accordance with variables, such as the
resistivity of a layer and efficiency of operation, wherein contact layer
resistivity and operating efficiency both increase with increase in band gap
(Final Rej. 4--5; Wanlass, i-fi-162 and 66). The Examiner concludes that,
accordingly, one skilled in the art would consider the band gap of the contact
traversing the Examiner's rejection based on the band gap limitations of
claim 1
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Application 12/218,558
layer as a result effective variable that can be optimized by routine
experimentation to obtain a desired balance between layer resistivity and
operation efficiency (Final Rej. 5).
Appellants contend that, in contrast to Wanlass, the present invention
provides a multijunction solar cell, and methods of manufacturing thereof,
that possess a contact layer having a band gap not only greater than the
adjacent subcell, but also greater than one or more subcells on the opposing
side of a graded interlayer, which allows for the contact layer to fully
transmit light that can be reflected from the ohmic mirror back through
adjacent solar cells (and avoid loss of heat energy) (App. Br. 7-8).
Appellants contend that there is no teaching in Wanlass of such high band
gap contact layers (App. Br. 8).
Appellants further contend that Wanlass does not disclose that "all
layers" below a preceding layer should have a greater band gap and that the
Examiner's analysis of Wanlass is unclear as to the orientation of "preceding
layers" and subcells discussed by Examiner (App. Br. 8-10). Appellants
contend that Wanlass actually suggests its contact layer having a band gap
value that is the same as the lower subcell but does not suggest the contact
layer having a higher band gap than that of a preceding layer. (App. Br. 9-
10). Appellants further contend that the band gap of the contact layer is not
a recognized result effective variable and that the Examiner has not provided
any evidence to support the conclusion that the contact layer band gap would
have been optimized by routine experimentation. (App. Br. 10; Reply Brief
entered February 26, 2014 ("Reply Br.") 3). Appellants also contend that it
would not have been obvious to add aluminum because "accepted wisdom"
teaches against this modification (App. Br. 11 ).
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We have fully considered Appellants' arguments and we find that the
preponderance of the evidence favors the Examiner's conclusion of
obviousness within the meaning of§ 103. Contrary to Appellants'
contentions, the Examiner reasonably established that a person skilled in the
art would have understood from Wanlass' teachings that the band gap of the
contact layer (a non-active semiconductor layer) can be increased by adding
aluminum and arrive at a band gap as high or greater than that of the subcells
(active semiconductor layers) within its multijunction solar cell (Ans. 4--5).
In view of Wanlass' teachings, the ordinarily skilled artisan would have
appreciated that increasing the band gap of the contact layer would allow
more light to be transmitted to the mirror layer and thus reflected back to the
subcells to avoid unnecessarily heating the solar cell, as found by the
Examiner (Ans. 5). The prior art's recognition that grading layers (non-
active semiconductor layers) should possess a higher band gap than adjacent
subcells (active semiconductor layers) to permit transmission of light is a
strong suggestion to modify the band gap of the contact layer accordingly so
that non-absorbed solar radiation is reflected back to the subcells thereby
minimizing loss of energy (Ans. 5; Wanlass, i-fi-134, 62 and 66).
We further find unpersuasive Appellants' arguments as to the
orientation of the preceding layers. We agree with the Examiner that, as
evidenced by Figure 3d, reference numbers 34 and 36 clearly demonstrate
that the light is entering from the bottom of the solar photovoltaic converter
depicted in Wanlass' Figure 1 and that the band gaps are decreasing for the
subcells as light goes through the converter (Ans. 6-8). Consequently, the
band gaps for the subcells decrease as the light is transmitted from the
substrate towards the back portion of Wanlass' multijunction solar cell
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(contact layer). We further agree with the Examiner that Wanlass, in the
embodiment represented by Fig. 1, is disclosing the active semiconductor
layers (e.g., subcells) as decreasing in band gap whereas non-active
semiconductor layers (e.g., grading layers) have higher band gaps in
comparison to the non-active semiconductor layers (Ans. 7-8). We further
agree with the Examiner that the presence of the reflecting mirror in
Wanlass' solar cell would have suggested to one in the art to select/prepare a
contact layer with a high band gap value (e.g. by adding aluminum as
suggested by Wanlass) so that more solar radiation is transmitted through the
contact layer and reflected back to the subcells for electricity production
instead of undesirably heating of the solar cells (Ans. 9-11).
We are also not persuaded by Appellants' arguments traversing the
Examiner's finding of the band gap value for the contact layer as a result-
effective variable. We agree with the Examiner that Appellants' reliance on
the disclosure in i-f20 of the Specification as evidence of conventionally low
band gaps for contact layers in order to keep the resistance of the contact
layer low as unpersuasive because this disclosure relates to embodiments not
possessing a reflecting layer over the contact layer (Ans. 9-11; Reply Br. 4).
Appellants' arguments are therefore drawn to contact layers in a solar cell
having a specific embodiment and are not drawn to a general teaching of
band gaps in multijunction solar cells that encompass the embodiment
recited in the present claims. Moreover, contrary to Appellants' position,
Wanlass discloses that exact bandgap values can be the product of empirical
optimization depending upon the operating conditions and subcell
performance (Wanlass, i-fi-162 and 66). In other words, one of ordinary skill in
the art would have understood that Wanlass would have suggested that the
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Application 12/218,558
contact layer in a mirror-backed solar cell have a band gap greater than the
subcells in order to permit solar radiation to pass through the layer and be
reflected back to the subcells for electricity production. The ordinarily
skilled artisan would have understood that the increase in resistance of the
contact layer by the addition of aluminum as argued by Appellants would
have been a trade-off for the increase in solar radiation transmission.
Furthermore, Appellants have not submitted any evidence showing
that the contact layer having a high band gap provides an unexpected result
(see generally App. Br.; Reply Br.). See In re Boesch, 617 F.2d 272, 276
(CCPA 1980). Note also Jn re Woodruff, 919 F.2d 1575, 1578 (Fed. Cir.
1990), and ln re Aller, 220 F.2d 454, 456 (CCPA 1955).
Accordingly, we affirm the Examiner's rejection of claims 1, 3, 5-11,
15, 16 and 50 under 35 U.S.C. § 103(a) as unpatentable over Wanlass.
REJECTIONS (II) and (III): Claims 12-14, 18-21, and 24--28.
Appellants submit that the deficiencies of Wanlass as applied to
independent claim 21, and dependent claims 12-14, 18-20 and 24--28, are
the same or similar to the deficiencies of Wanlass as applied in Rejection I
and that neither King nor Iles provide that which is missing from Wanlass.
However, as discussed previously, Appellants' arguments traversing
the Examiner's findings in Rejection I have been deemed unavailing.
Thus, based on this record, we sustain these rejections.
REJECTION (IV)
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Appellants have not proffered any substantive arguments traversing
the grounds of the obviousness double patenting rejection of the present
claims over U.S. 11/860, 183 and Wanlass.
Thus, we summarily affirm this rejection.
CONCLUSION
Accordingly, on this record and for the above reasons, we sustain the
35 U.S.C. § 103 Rejections (I-III) of the present claims over the cited prior
art and Rejection IV of the present claims on the grounds of nonstatutory
obviousness double patenting.
DECISION
The Examiner's § 103 and obviousness-double patenting rejections are
affirmed.
No time period for taking any subsequent action in connection with
this appeal may be extended under 37 C.F.R. § 1.136(a).
AFFIRMED
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