CONVERTIBLE PROMISSORY NOTE

Exhibit 10.15

THIS CONVERTIBLE PROMISSORY NOTE AND THE SECURITIES INTO WHICH IT MAY BE CONVERTED HAVE NOT BEEN REGISTERED UNDER THE SECURITIES ACT OF 1933, AS AMENDED (THE “SECURITIES ACT”), IN RELIANCE UPON AN EXEMPTION FROM REGISTRATION UNDER THE SECURITIES ACT, AND, ACCORDINGLY, MAY NOT BE OFFERED OR SOLD EXCEPT PURSUANT TO AN EFFECTIVE REGISTRATION STATEMENT UNDER THE SECURITIES ACT OR PURSUANT TO AN AVAILABLE EXEMPTION FROM, OR IN A TRANSACTION NOT SUBJECT TO, THE REGISTRATION REQUIREMENTS OF THE SECURITIES ACT.

CONVERTIBLE PROMISSORY NOTE

L&L Acquisition Corp., a Delaware corporation (“Maker”), promises to pay to the order of LLM Structured Equity Fund L.P. or its registered assigns or successors in interest (“Payee”), or order, the principal sum of Two Hundred Thousand Dollars ($200,000) in lawful money of the United States of America, on the terms and conditions described below. All payments on this Note shall be made by check or wire transfer of immediately available funds or as otherwise determined by Maker to such account as Payee may from time to time designate by written notice in accordance with the provisions of this Note.

1. Principal. The principal balance of this Promissory Note (this “Note”) shall be payable on the earlier of (i) May 29, 2012 or (ii) the date on which Maker consummates a Business Combination (as defined in Maker’s Amended and Restated Certificate of Incorporation), subject to the Warrant Conversion Option as set forth in Section 5 below. The principal balance may be prepaid at any time.

2. Interest. No interest shall accrue on the unpaid principal balance of this Note.

3. Application of Payments. All payments shall be applied first to payment in full of any costs incurred in the collection of any sum due under this Note, including (without limitation) reasonable attorney’s fees, then to the payment in full of any late charges and finally to the reduction of the unpaid principal balance of this Note.

4. Events of Default. The following shall constitute an event of default (“Event of Default”):

(a) Failure to Make Required Payments. Failure by Maker to pay the principal of this Note within five (5) business days following the date when due.

(b) Voluntary Bankruptcy, Etc. The commencement by Maker of a voluntary case under the Federal Bankruptcy Code, as now constituted or hereafter amended, or any other applicable federal or state bankruptcy, insolvency, reorganization, rehabilitation or other similar law, or the consent by it to the appointment of or taking possession by a receiver, liquidator, assignee, trustee, custodian, sequestrator (or other similar official) of Maker or for any substantial part of its property, or the making by it of any assignment for the benefit of creditors, or the failure of Maker generally to pay its debts as such debts become due, or the taking of corporate action by Maker in furtherance of any of the foregoing.

(c) Involuntary Bankruptcy, Etc. The entry of a decree or order for relief by a court having jurisdiction in the premises in respect of Maker in an involuntary case under the Federal Bankruptcy Code, as now or hereafter constituted, or any other applicable federal or state bankruptcy, insolvency or other similar law, or appointing a receiver, liquidator, assignee, custodian, trustee, sequestrator (or similar official) of Maker or for any substantial part of its property, or ordering the winding-up or liquidation of its affairs, and the continuance of any such decree or order unstayed and in effect for a period of 60 consecutive days.

5. Warrant Conversion Option. In the event that Maker enters into a definitive agreement to consummate a Business Combination, then no later than five (5) business days prior to the consummation thereof, Payee, in its sole discretion, may notify Maker of its intent to convert up to the then remaining principal amount of this Note into warrants to purchase shares of common stock of Maker (or, if Maker merges with another

entity in connection with the Business Combination, the surviving entity in such merger) at a price of $0.75 per warrant. Such warrants shall be in the same form as the private placement warrants as described in the prospectus filed by Maker with the Securities and Exchange Commission (the “SEC”) in connection with its initial public offering (the “IPO”). Such conversion shall be effective on the date of consummation of the Business Combination (it being understood and agreed that no amount hereunder shall be convertible into warrants if a Business Combination is not consummated).

6. Remedies.

(a) Upon the occurrence of an Event of Default specified in Section 4(a) hereof, Payee may, by written notice to Maker, declare this Note to be due immediately and payable, whereupon the unpaid principal amount of this Note, and all other amounts payable thereunder, shall become immediately due and payable without presentment, demand, protest or other notice of any kind, all of which are hereby expressly waived, anything contained herein or in the documents evidencing the same to the contrary notwithstanding.

(b) Upon the occurrence of an Event of Default specified in Sections 4(b) and 4(c), the unpaid principal balance of this Note, and all other sums payable with regard to this Note, shall automatically and immediately become due and payable, in all cases without any action on the part of Payee.

7. Waivers. Maker and all endorsers and guarantors of, and sureties for, this Note waive presentment for payment, demand, notice of dishonor, protest, and notice of protest with regard to the Note, all errors, defects and imperfections in any proceedings instituted by Payee under the terms of this Note, and all benefits that might accrue to Maker by virtue of any present or future laws exempting any property, real or personal, or any part of the proceeds arising from any sale of any such property, from attachment, levy or sale under execution, or providing for any stay of execution, exemption from civil process, or extension of time for payment; and Maker agrees that any real estate that may be levied upon pursuant to a judgment obtained by virtue hereof, on any writ of execution issued hereon, may be sold upon any such writ in whole or in part in any order desired by Payee.

8. Unconditional Liability. Maker hereby waives all notices in connection with the delivery, acceptance, performance, default, or enforcement of the payment of this Note, and agrees that its liability shall be unconditional, without regard to the liability of any other party, and shall not be affected in any manner by any indulgence, extension of time, renewal, waiver or modification granted or consented to by Payee, and consents to any and all extensions of time, renewals, waivers, or modifications that may be granted by Payee with respect to the payment or other provisions of this Note, and agrees that additional makers, endorsers, guarantors, or sureties may become parties hereto without notice to Maker or affecting Maker’s liability hereunder.

9. Notices. Any notice called for hereunder shall be deemed properly given if (i) sent by certified mail, return receipt requested, (ii) personally delivered, (iii) dispatched by any form of private or governmental express mail or delivery service providing receipted delivery or (iv) sent by telefacsimile or (v) to the following addresses or to such other address as either party may designate by notice in accordance with this Section:

If to Maker:

L&L Acquisition Corp.

265 Franklin Street, 20^th Floor

Boston, MA 02110

Attn: Peter Schofield, Chief Financial Officer

If to Payee:

LLM Structured Equity Fund L.P.

265 Franklin Street, 20^th Floor

Boston, MA 02110

Attn: Peter Schofield, Chief Financial Officer

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Notice shall be deemed given on the earlier of (i) actual receipt by the receiving party, (ii) the date shown on a telefacsimile transmission confirmation, (iii) the date reflected on a signed delivery receipt, or (iv) two (2) Business Days following tender of delivery or dispatch by express mail or delivery service.

10. Construction. THIS NOTE SHALL BE CONSTRUED AND ENFORCED IN ACCORDANCE WITH THE LAWS OF THE COMMONWEALTH OF MASSACHUSETTS, WITHOUT REGARD TO CONFLICT OF LAW PROVISIONS THEREOF.

11. Severability. Any provision contained in this Note which is prohibited or unenforceable in any jurisdiction shall, as to such jurisdiction, be ineffective to the extent of such prohibition or unenforceability without invalidating the remaining provisions hereof, and any such prohibition or unenforceability in any jurisdiction shall not invalidate or render unenforceable such provision in any other jurisdiction.

12. Trust Waiver. Notwithstanding anything herein to the contrary, Payee hereby waives any and all right, title, interest or claim of any kind (“Claim”) in or to any distribution of the trust account in which the proceeds of the IPO conducted by Maker (including the deferred underwriters discounts and commissions) and the proceeds of the sale of the warrants issued in a private placement that occurred prior to the effectiveness of the IPO, as described in greater detail in the registration statement and prospectus filed with the SEC in connection with the IPO, were deposited, and hereby agrees not to seek recourse, reimbursement, payment or satisfaction for any Claim against the trust account for any reason whatsoever.

13. Amendment; Waiver. Any amendment hereto or waiver of any provision hereof may be made with, and only with, the written consent of Maker and Payee.

14. Assignment. No assignment or transfer of this Note or any rights or obligations hereunder may be made by any party hereto (by operation of law or otherwise) without the prior written consent of the other party hereto and any attempted assignment without the required consent shall be void.

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IN WITNESS WHEREOF, Maker, intending to be legally bound hereby, has caused this Note to be duly executed by an authorized officer as of the day and year first above written.