Ex Parte Varghese et al

Patent Trial and Appeal BoardApr 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. Â§ 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. Â§ 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; 2 Appeal2014-004860 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. Â§ 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. Â§ 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. Â§ 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. Â§ 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. 3 Appeal2014-004860 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 4 Appeal2014-004860 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 5 Appeal2014-004860 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 ). 6 Appeal2014-004860 Application 12/218,558 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 ofÂ§ 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 7 Appeal2014-004860 Application 12/218,558 (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 8 Appeal2014-004860 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. Â§ 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) 9 Appeal2014-004860 Application 12/218,558 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. Â§ 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 Â§ 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. Â§ 1.136(a). AFFIRMED 10