Exhibit 4.3


 


THE REGISTERED HOLDER OF THIS PURCHASE
OPTION BY ITS ACCEPTANCE HEREOF AGREES THAT IT WILL NOT SELL, TRANSFER OR ASSIGN THIS PURCHASE OPTION EXCEPT AS HEREIN PROVIDED
AND THE REGISTERED HOLDER OF THIS PURCHASE OPTION AGREES THAT IT WILL NOT SELL, TRANSFER, ASSIGN, PLEDGE OR HYPOTHECATE THIS PURCHASE
OPTION OR CAUSE IT TO BE THE SUBJECT OF ANY HEDGING, SHORT SALE, DERIVATIVE, PUT, OR CALL TRANSACTION THAT WOULD RESULT IN THE
EFFECTIVE ECONOMIC DISPOSITION OF THE PURCHASE OPTION BY ANY PERSON FOR A PERIOD OF ONE HUNDRED EIGHTY DAYS FOLLOWING THE EFFECTIVE
DATE (AS DEFINED HEREIN) TO ANYONE OTHER THAN TO (I) CHARDAN CAPITAL MARKETS, LLC (“CHARDAN”) OR AN UNDERWRITER
OR SELECTED DEALER PARTICIPATING IN THE OFFERING OR (II) AN OFFICER OR PARTNER OF CHARDAN OR OF ANY SUCH UNDERWRITER OR SELECTED
DEALER AND IN ACCORDANCE WITH FINRA RULE 5110(G)(2).


 


THIS PURCHASE OPTION IS NOT EXERCISABLE
PRIOR TO THE LATER OF THE CONSUMMATION BY ORISUN ACQUISITION CORP. (THE “COMPANY”) OF A MERGER, SHARE
EXCHANGE, ASSET ACQUISITION, RECAPITALIZATION, REORGANIZATION OR OTHER SIMILAR BUSINESS COMBINATION (THE “BUSINESS
COMBINATION”) (AS DESCRIBED MORE FULLY IN THE COMPANY’S REGISTRATION STATEMENT (DEFINED HEREIN)) AND FEBRUARY
2, 2020. VOID AFTER 5:00 P.M. NEW YORK CITY LOCAL TIME, ON THE EXPIRATION DATE (DEFINED HEREIN).


 


UNIT PURCHASE OPTION

FOR THE PURCHASE OF

UP TO 300,000 UNITS

OF

ORISUN ACQUISITION CORP.


 


1.
PURCHASE OPTION.


 


THIS CERTIFIES THAT, in consideration of
$100.00 duly paid by or on behalf of Chardan Capital Markets, LLC (the “Holder”), as registered owner
of this Purchase Option, to Orisun Acquisition Corp. (the “Company”), Holder is entitled, at any time
or from time to time upon the later of the consummation of a Business Combination or February 2, 2020 (the “Commencement
Date”), and at or before 5:00 p.m., New York City local time, on the five year anniversary of the effective date
(the “Effective Date”) of the Company’s registration statement (the “Registration Statement”)
pursuant to which Units are offered for sale to the public in the Company’s initial public offering (the “Offering”),
but not thereafter (the “Expiration Date”), to subscribe for, purchase and receive, in whole or in part,
up to Three Hundred Thousand (300,000) units (“Units”) of the Company, each Unit consisting of one (1)
share of common stock, par value $0.00001 per share, of the Company (“Share(s)”), one (1) warrant (“Warrant(s)”),
each Warrant entitling the holder thereof to purchase one-half (1/2) of one Share and one (1) right to receive one-tenth (1/10)
of a Share upon the consummation of a Business Combination (“Right(s)”). Each Right has the same terms
as the rights included in the units being registered for sale to the public by way of the Registration Statement (“Public
Rights”). Each Warrant has the same terms as the warrants included in the Units being registered for sale to the
public by way of the Registration Statement (the “Public Warrants”). Notwithstanding anything to the
contrary, the original Holder of this Purchase Option agrees that it will not be permitted to exercise his Purchase Option or the
Warrants underlying this Purchase Option after the five year anniversary of the Effective Date. During the period ending on the
Expiration Date, the Company agrees not to take any action that would terminate the Purchase Option. This Purchase Option is initially
exercisable at $11.50 per Unit so purchased; provided, however, that upon the occurrence of any of the events specified
in Section 6 hereof, the rights granted by this Purchase Option, including the exercise price per Unit and the number of
Units (and Shares, Warrants and Rights) to be received upon such exercise, shall be adjusted as therein specified. The term “Exercise
Price” shall mean the initial exercise price or the adjusted exercise price, depending on the context.


 


2.
EXERCISE OF PURCHASE OPTION.


 


2.1 Exercise Form. In order to exercise
this Purchase Option, the exercise form attached hereto must be duly executed and completed and delivered to the Company, together
with this Purchase Option and payment of the Exercise Price for the Units being purchased payable in cash or by certified check
or official bank check or pursuant to Section 2.3 hereof. If the subscription rights represented hereby shall not be exercised
at or before 5:00 p.m., New York City local time, on the Expiration Date, this Purchase Option shall become and be void without
further force or effect, and all rights represented hereby shall cease and expire.


 




     


     


    

 


2.2 Legend. Each certificate for
the securities purchased under this Purchase Option shall bear a legend as follows, unless such securities have been registered
under the Securities Act of 1933, as amended (“Act”):


 


“The securities represented by this certificate
have not been registered under the Securities Act of 1933, as amended (“Act”) or the laws of applicable states or other
jurisdictions. The securities may not be offered for sale, sold or otherwise transferred except pursuant to an effective registration
statement under the Act, or pursuant to an exemption from registration under the Act and applicable laws of states or other jurisdictions.”


 


2.3 Cashless Exercise.


 


2.3.1 Determination of Amount. In lieu
of the payment of the Exercise Price multiplied by the number of Units for which this Purchase Option is exercisable (and in lieu
of being entitled to receive Shares and Warrants) in the manner required by Section 2.1, and subject to Section 6.1
hereof, the Holder shall have the right (but not the obligation) to convert any exercisable but unexercised portion of this Purchase
Option into Units (“Cashless Exercise Right”) as follows: upon exercise of the Cashless Exercise Right,
the Company shall deliver to the Holder (without payment by the Holder of any of the Exercise Price in cash) that number of Units
(or that number of Shares, Warrants and Rights comprising that number of Units) equal to the number of Units to be exercised multiplied
by the quotient obtained by dividing (x) the “Value” (as defined below) of the portion of the Purchase Option being
converted by (y) the Current Market Value (as defined below). The “Value” of the portion of the Purchase
Option being converted shall equal the remainder derived from subtracting (a) (i) the Exercise Price multiplied by (ii) the number
of Units underlying the portion of this Purchase Option being converted from (b) the Current Market Value of a Unit multiplied
by the number of Units underlying the portion of the Purchase Option being converted. As used herein, the term “Current
Market Value” per Unit at any date means: (A) in the event that the Units, Shares, Public Rights and Public Warrants
are still trading, (i) if the Units are listed on a national securities exchange, the average reported last sale price of the Units
in the principal trading market for the Units as reported by the exchange, as the case may be, for the three trading days preceding
the date in question; or (ii) if the Units are not listed on a national securities exchange, but is traded in the over-the-counter
market, the average reported last sale price for Units for the three trading days preceding the date in question for which such
quotations are reported by the OTC Markets Group Inc., or similar publisher of such quotations; (B) in the event that the Units
are not still trading but the Shares, Public Rights, and Public Warrants underlying the Units are still trading, the aggregate
of (i) the product of (x) the Current Market Price of the Share and (y) the number of the Shares underlying one Unit (which shall
include the portion of a Share the holder of a Unit would automatically receive in connection with the Right included in each such
Unit), plus (ii) the product of (x) the Current Market Price of the Public Warrants and (y) the number of Warrants included in
one Unit; or (C) in the event that neither the Units nor the Public Warrants are still trading, the aggregate of (i) the product
of (x) the Current Market Price of the Shares and (y) the number of the Shares underlying one Unit (which shall include the portion
of a Share the holder of a Unit would automatically receive in connection with the Right included in each such Unit), plus (ii)
the remainder derived from subtracting (x) the exercise price of the Warrants multiplied by the number of Shares issuable upon
exercise of the Warrants underlying one Unit from (y) the product of (aa) the Current Market Price of the Shares multiplied by
(bb) the number of Shares underlying the Warrants included in each such Unit. The “Current Market Price” shall mean
(i) if the Shares (or Public Warrants, as the case may be) are listed on a national securities exchange, the average reported last
sale price of the Shares (or Public Warrants) in the principal trading market for the Share (or Public Warrants) as reported by
the exchange, as the case may be, for the three trading days preceding the date in question; (ii) if the Shares (or Public Warrants)
are not listed on a national securities exchange, but are traded in the over-the-counter market, the average reported last sale
price for the Share (or Public Warrants) for the three (3) trading days preceding the date in question for which such quotations
are reported by the OTC Markets Group Inc., or similar publisher of such quotations; and (iii) if the fair market value of the
Share cannot be determined pursuant to clause (i) or (ii) above, such price as the Board of Directors of the Company shall determine,
in good faith. In the event the Public Warrants have expired and are no longer exercisable, no “Value” shall be attributed
to the Warrants underlying this Purchase Option.


 




    2


     


    

 


2.3.2 Mechanics of Cashless Exercise.
The Cashless Exercise Right may be exercised by the Holder on any business day on or after the Commencement Date and not later
than the Expiration Date by delivering the Purchase Option with the duly executed exercise form attached hereto with the cashless
exercise section completed to the Company, exercising the Cashless Exercise Right and specifying the total number of Units the
Holder will purchase pursuant to such Cashless Exercise Right


 


2.4 No Obligation to Net Cash Settle.
Notwithstanding anything to the contrary contained in this Purchase Option, in no event will the Company be required to net cash
settle the exercise of the Purchase Option or Warrants underlying the Purchase Option. The holder of the Purchase Option and Warrants
underlying the Purchase Option will not be entitled to exercise the Purchase Option or the Warrants underlying such Purchase Option
unless it exercises such Purchase Option pursuant to the Cashless Exercise Right or a registration statement is effective, or an
exemption from the registration requirements is available at such time and, if the holder is not able to exercise the Purchase
Option or underlying Warrants, the Purchase Option and/or the underlying Warrants, as applicable, will expire worthless.


 


3.
TRANSFER OF PURCHASE OPTION.


 


3.1 General Restrictions. The registered
Holder of this Purchase Option, by its acceptance hereof, agrees that it will not sell, transfer, assign, pledge or hypothecate
this Purchase Option (or the Shares, Rights and Warrants underlying this Purchase Option), or cause the Purchase Option (or the
Shares, Rights and Warrants underlying this Purchase Option) to be the subject of any hedging, short sale, derivative, put, or
call transaction that would result in the effective economic disposition of the Purchase Option by any person, for a period of
180 days (pursuant to Rule 5110(g)(1) of the Conduct Rules of the Financial Industry Regulatory Authority (FINRA))
following the Effective Date to anyone other than (i) Chardan or an underwriter or selected dealer in connection with the Offering,
or (ii) a bona fide officer or partner of Chardan or of any such underwriter or selected dealer. On and after the 181st day following
the Effective Date, transfers to others may be made subject to compliance with or exemptions from applicable securities laws. In
order to make any permitted assignment, the Holder must deliver to the Company the assignment form attached hereto duly executed
and completed, together with the Purchase Option and payment of all transfer taxes, if any, payable in connection therewith. The
Company shall within 5 business days transfer this Purchase Option on the books of the Company and shall execute and deliver a
new Purchase Option of like tenor to the appropriate assignee(s) expressly evidencing the right to purchase the aggregate number
of Units purchasable hereunder or such portion of such number as shall be contemplated by any such assignment.


 


3.2 Restrictions Imposed by the Act.
The securities evidenced by this Purchase Option shall not be transferred unless and until (i) the Company has received the opinion
of counsel for the Holder that the securities may be transferred pursuant to an exemption from registration under the Act and applicable
state securities laws, the availability of which is established to the reasonable satisfaction of the Company (the Company hereby
agreeing that the opinion of Ellenoff Grossman & Schole LLP shall be deemed satisfactory evidence of the availability of an
exemption), or (ii) a registration statement or a post-effective amendment to the Registration Statement relating to such securities
has been filed by the Company and declared effective by the Securities and Exchange Commission (the “Commission”)
and compliance with applicable state securities law has been established.


 


4.
NEW PURCHASE OPTION TO BE ISSUED.


 


4.1 Partial Exercise or Transfer.
Subject to the restrictions in Section 3 hereof, this Purchase Option may be exercised or assigned in whole or in part.
In the event of the exercise or assignment hereof in part only, upon surrender of this Purchase Option for cancellation, together
with the duly executed exercise or assignment form and funds sufficient to pay any Exercise Price (except to the extent that the
Holder elects to exercise this Purchase Option by means of a cashless exercise as provided in Section 2.3 above) and/or
transfer tax, the Company shall cause to be delivered to the Holder without charge a new Purchase Option of like tenor to this
Purchase Option in the name of the Holder evidencing the right of the Holder to purchase the number of Units purchasable hereunder
as to which this Purchase Option has not been exercised or assigned


 


4.2 Lost Certificate. Upon receipt
by the Company of evidence satisfactory to it of the loss, theft, destruction or mutilation of this Purchase Option and of reasonably
satisfactory indemnification or the posting of a bond, the Company shall execute and deliver a new Purchase Option of like tenor
and date. Any such new Purchase Option executed and delivered as a result of such loss, theft, mutilation or destruction shall
constitute a substitute contractual obligation on the part of the Company.


 




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5.
REGISTRATION RIGHTS.


 


5.1 Demand Registration.


 


5.1.1 Grant of Right. The Company,
upon written demand (“Initial Demand Notice”) of the Holder(s) of at least 51% of the Purchase Option
and/or the underlying Units and/or the underlying securities (“Majority Holders”), agrees to use its
best efforts to register (the “Demand Registration”) under the Act on one occasion, all or any portion
of the Purchase Option requested by the Majority Holders in the Initial Demand Notice and all of the securities underlying such
Purchase Option, including the Units, Shares, Warrants and the Shares underlying the Warrants and Rights (collectively, the “Registrable
Securities”). On such occasion, the Company will use its best efforts to file a registration statement or a post-effective
amendment to the Registration Statement covering the Registrable Securities as expeditiously as possible after receipt of the Initial
Demand Notice and use its best efforts to have such registration statement or post-effective amendment declared effective as soon
as possible thereafter. The demand for registration may be made at any time during a period of five years beginning on the Effective
Date. The Initial Demand Notice shall specify the number of shares of Registrable Securities proposed to be sold and the intended
method(s) of distribution thereof. The Company will notify all holders of the Purchase Option and/or Registrable Securities of
the demand within ten days from the date of the receipt of any such Initial Demand Notice. Each holder of Registrable Securities
who wishes to include all or a portion of such holder’s Registrable Securities in the Demand Registration (each such holder
including shares of Registrable Securities in such registration, a “Demanding Holder”) shall so notify
the Company within fifteen (15) days after the receipt by the holder of the notice from the Company. Upon any such request, the
Demanding Holders shall be entitled to have their Registrable Securities included in the Demand Registration, subject to Section
5.1.4. The Company shall not be required to effect more than one (1) Demand Registration under this Section 5.1 in respect
of all Registrable Securities.


 


5.1.2 Effective Registration. Notwithstanding
Section 5.1.5, a registration will not count as a Demand Registration until the registration statement filed with the Commission,
with respect to such Demand Registration, has been declared effective and the Company has complied with all of its obligations
under this Purchase Option with respect thereto.


 


5.1.3 Underwritten Offering. If the
Majority Holders so elect and such holders so advise the Company as part of the Initial Demand Notice, the offering of such Registrable
Securities pursuant to such Demand Registration shall be in the form of an underwritten offering. In such event, the right of any
holder to include its Registrable Securities in such registration shall be conditioned upon such holder’s participation in
such underwriting and the inclusion of such holder’s Registrable Securities in the underwriting to the extent provided herein.
All Demanding Holders proposing to distribute their securities through such underwriting shall enter into an underwriting agreement
in customary form with the underwriter or underwriters selected for such underwriting by the Majority Holders.


 


5.1.4 Reduction of Offering. If the
managing underwriter or underwriters for a Demand Registration that is to be an underwritten offering advises the Company and the
Demanding Holders in writing that the dollar amount or number of shares of Registrable Securities which the Demanding Holders desire
to sell, taken together with all other Shares or other securities which the Company desires to sell and the Shares, if any, as
to which registration has been requested pursuant to written contractual piggy-back registration rights held by other shareholders
of the Company who desire to sell, exceeds the maximum dollar amount or maximum number of shares that can be sold in such offering
without adversely affecting the proposed offering price, the timing, the distribution method, or the probability of success of
such offering (such maximum dollar amount or maximum number of shares, as applicable, the “Maximum Number of Shares”),
then the Company shall include in such registration: (i) first, the Registrable Securities as to which Demand Registration has
been requested by the Demanding Holders (pro rata in accordance with the number of shares that each such person has requested be
included in such registration, regardless of the number of shares held by each such person (such proportion is referred to herein
as “Pro Rata”)) that can be sold without exceeding the Maximum Number of Shares; (ii) second, to the
extent that the Maximum Number of Shares has not been reached under the foregoing clause (i), the Shares or other securities that
the Company desires to sell that can be sold without exceeding the Maximum Number of Shares; (iii) third, to the extent that the
Maximum Number of Shares has not been reached under the foregoing clauses (i) and (ii), the Shares or other securities registrable
pursuant to the terms of the Registration Rights Agreement between the Company and the initial investors in the Company and Chardan,
dated as of August 2, 2019 (the “Registration Rights Agreement” and such registrable securities, the
“Investor Securities”) as to which “piggy-back” registration has been requested by the holders
thereof, Pro Rata, that can be sold without exceeding the Maximum Number of Shares; and (iv) fourth, to the extent that the Maximum
Number of Shares has not been reached under the foregoing clauses (i), (ii), and (iii), the Shares or other securities for the
account of other persons that the Company is obligated to register pursuant to written contractual arrangements with such persons
and that can be sold without exceeding the Maximum Number of Shares.


 




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5.1.5 Withdrawal. If a majority-in-interest
of the Demanding Holders disapprove of the terms of any underwriting or are not entitled to include all of their Registrable Securities
in any offering, such majority-in-interest of the Demanding Holders may elect to withdraw from such offering by giving written
notice to the Company and the underwriter or underwriters of their request to withdraw prior to the effectiveness of the registration
statement filed with the Commission with respect to such Demand Registration. If the majority-in-interest of the Demanding Holders
withdraws from a proposed offering relating to a Demand Registration, then the Company does not have to continue its obligations
under Section 5.1, provided that, any such withdrawal will not count as the Demand Registration if the Demanding
Holders pay all of the Company’s out-of-pocket expenses, with respect to such withdrawn registration.


 


5.1.6 Terms. The Company shall bear
all fees and expenses attendant to registering the Registrable Securities, including the expenses of one legal counsel selected
by the Holders to represent them in connection with the sale of the Registrable Securities, but the Holders shall pay any and all
underwriting commissions. The Company agrees to use its reasonable best efforts to qualify or register the Registrable Securities
in such states as are reasonably requested by the Majority Holder(s); provided, however, that in no event shall the
Company be required to register the Registrable Securities in a state in which such registration would cause (i) the Company to
be obligated to qualify to do business in such state, or would subject the Company to taxation as a foreign corporation doing business
in such jurisdiction or (ii) the principal shareholders of the Company to be obligated to escrow their shares of capital stock
of the Company. The Company shall use its best efforts to cause any registration statement or post-effective amendment filed pursuant
to the demand rights granted under Section 5.1.1 to remain effective for a period of nine consecutive months from the effective
date of such registration statement or post-effective amendment.


 


5.2 Piggy-Back Registration.


 


5.2.1 Piggy-Back Rights. If at any
time during the seven year period commencing on the Effective Date the Company proposes to file a registration statement under
the Act with respect to an offering of equity securities, or securities or other obligations exercisable or exchangeable for, or
convertible into, equity securities, by the Company for its own account or for shareholders of the Company for their account (or
by the Company and by shareholders of the Company including, without limitation, pursuant to Section 5.1), other than a
registration statement (i) filed in connection with any employee stock option or other benefit plan, (ii) for an exchange offer
or offering of securities solely to the Company’s existing shareholders, (iii) for an offering of debt that is convertible
into equity securities of the Company or (iv) for a dividend reinvestment plan, then the Company shall (x) give written notice
of such proposed filing to the holders of Registrable Securities as soon as practicable but in no event less than ten (10) days
before the anticipated filing date, which notice shall describe the amount and type of securities to be included in such offering,
the intended method(s) of distribution, and the name of the proposed managing underwriter or underwriters, if any, of the offering,
and (y) offer to the holders of Registrable Securities in such notice the opportunity to register the sale of such number of shares
of Registrable Securities as such holders may request in writing within five (5) days following receipt of such notice (a “Piggy-Back
Registration”). The Company shall cause such Registrable Securities to be included in such registration and shall
use its best efforts to cause the managing underwriter or underwriters of a proposed underwritten offering to permit the Registrable
Securities requested to be included in a Piggy-Back Registration on the same terms and conditions as any similar securities of
the Company and to permit the sale or other disposition of such Registrable Securities in accordance with the intended method(s)
of distribution thereof. All holders of Registrable Securities proposing to distribute their securities through a Piggy-Back Registration
that involves an underwriter or underwriters shall enter into an underwriting agreement in customary form with the underwriter
or underwriters selected for such Piggy-Back Registration


 




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5.2.2 Reduction of Offering. If the
managing underwriter or underwriters for a Piggy-Back Registration that is to be an underwritten offering advises the Company and
the holders of Registrable Securities in writing that the dollar amount or number of Shares which the Company desires to sell,
taken together with Shares, if any, as to which registration has been demanded pursuant to written contractual arrangements with
persons other than the holders of Registrable Securities hereunder, the Registrable Securities as to which registration has been
requested under this Section 5.2, and the Shares, if any, as to which registration has been requested pursuant to the written
contractual piggy-back registration rights of other shareholders of the Company, exceeds the Maximum Number of Shares, then the
Company shall include in any such registration:


 


(a) If the registration
is undertaken for the Company’s account: (A) first, Shares or other securities that the Company desires to sell that can
be sold without exceeding the Maximum Number of Shares; (B) second, to the extent that the Maximum Number of Shares has not been
reached under the foregoing clause (A), the Shares or other securities, if any, comprised of Registrable Securities and Investor
Securities, as to which registration has been requested pursuant to the applicable written contractual piggy-back registration
rights of such security holders, Pro Rata, that can be sold without exceeding the Maximum Number of Shares; and (C) third, to the
extent that the Maximum Number of shares has not been reached under the foregoing clauses (A) and (B), the Shares or other securities
for the account of other persons that the Company is obligated to register pursuant to written contractual piggy-back registration
rights with such persons and that can be sold without exceeding the Maximum Number of Shares;


 


(b) If the registration
is a “demand” registration undertaken at the demand of holders of Investor Securities, (A) first, the Shares or other
securities for the account of the demanding persons, Pro Rata, that can be sold without exceeding the Maximum Number of Shares;
(B) second, to the extent that the Maximum Number of Shares has not been reached under the foregoing clause (A), the Shares or
other securities that the Company desires to sell that can be sold without exceeding the Maximum Number of Shares; (C) third, to
the extent that the Maximum Number of Shares has not been reached under the foregoing clauses (A) and (B), the shares of Registrable
Securities, Pro Rata, as to which registration has been requested pursuant to the terms hereof, that can be sold without exceeding
the Maximum Number of Shares; and (D) fourth, to the extent that the Maximum Number of Shares has not been reached under the foregoing
clauses (A), (B) and (C), the Shares or other securities for the account of other persons that the Company is obligated to register
pursuant to written contractual arrangements with such persons, that can be sold without exceeding the Maximum Number of Shares;
and


 


(c) If the registration
is a “demand” registration undertaken at the demand of persons other than either the holders of Registrable Securities
or of Investor Securities, (A) first, the Shares or other securities for the account of the demanding persons that can be sold
without exceeding the Maximum Number of Shares; (B) second, to the extent that the Maximum Number of Shares has not been reached
under the foregoing clause (A), the Shares or other securities that the Company desires to sell that can be sold without exceeding
the Maximum Number of Shares; (C) third, to the extent that the Maximum Number of Shares has not been reached under the foregoing
clauses (A) and (B), collectively the Shares or other securities comprised of Registrable Securities and Investor Securities, Pro
Rata, as to which registration has been requested pursuant to the terms hereof and of the Registration Rights Agreement, as applicable,
that can be sold without exceeding the Maximum Number of Shares; and (D) fourth, to the extent that the Maximum Number of Shares
has not been reached under the foregoing clauses (A), (B) and (C), the Shares or other securities for the account of other persons
that the Company is obligated to register pursuant to written contractual arrangements with such persons, that can be sold without
exceeding the Maximum Number of Shares.


 


5.2.3 Withdrawal. Any holder of Registrable
Securities may elect to withdraw such holder’s request for inclusion of Registrable Securities in any Piggy-Back Registration
by giving written notice to the Company of such request to withdraw prior to the effectiveness of the registration statement. The
Company (whether on its own determination or as the result of a withdrawal by persons making a demand pursuant to written contractual
obligations) may withdraw a registration statement at any time prior to the effectiveness of the registration statement. Notwithstanding
any such withdrawal, the Company shall pay all expenses incurred by the holders of Registrable Securities in connection with such
Piggy-Back Registration as provided in Section 5.2.4.


 




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5.2.4 Terms. The Company shall bear
all fees and expenses attendant to registering the Registrable Securities, including the expenses of one legal counsel selected
by the Holders to represent them in connection with the sale of the Registrable Securities but the Holders shall pay any and all
underwriting commissions related to the Registrable Securities. In the event of such a proposed registration, the Company shall
furnish the then Holders of outstanding Registrable Securities with not less than fifteen days written notice prior to the proposed
date of filing of such registration statement. Such notice to the Holders shall continue to be given for each applicable registration
statement filed (during the period in which the Purchase Option is exercisable) by the Company until such time as all of the Registrable
Securities have been registered and sold. The Holders of the Registrable Securities shall exercise the “piggy-back”
rights provided for herein by giving written notice within ten days of the receipt of the Company’s notice of its intention
to file a registration statement. The Company shall use its best efforts to cause any registration statement filed pursuant to
the above “piggyback” rights to remain effective for at least nine months from the date that the Holders of the Registrable
Securities are first given the opportunity to sell all of such securities.


 


5.3 General Terms.


 


5.3.1 Indemnification. The Company
shall, to the fullest extent permitted by applicable law, indemnify the Holder(s) of the Registrable Securities to be sold pursuant
to any registration statement hereunder and each person, if any, who controls such Holders within the meaning of Section 15 of
the Act or Section 20(a) of the Securities Exchange Act of 1934, as amended (“Exchange Act”), against
all loss, claim, damage, expense or liability (including all reasonable attorneys’ fees and other expenses reasonably incurred
in investigating, preparing or defending against litigation, commenced or threatened, or any claim whatsoever whether arising out
of any action between the underwriter and the Company or between the underwriter and any third party or otherwise) to which any
of them may become subject under the Act, the Exchange Act or otherwise, arising from such registration statement but only to the
same extent and with the same effect as the provisions pursuant to which the Company has agreed to indemnify the underwriters contained
in Section 5 of the Underwriting Agreement between the Company, Chardan and the other underwriters named therein dated the Effective
Date (“Underwriting Agreement”). The Holder(s) of the Registrable Securities to be sold pursuant to such
registration statement, and their successors and assigns, shall severally, and not jointly, indemnify the Company, its officers
and directors and each person, if any, who controls the Company within the meaning of Section 15 of the Act or Section 20(a) of
the Exchange Act, against all loss, claim, damage, expense or liability (including all reasonable attorneys’ fees and other
expenses reasonably incurred in investigating, preparing or defending against any claim whatsoever) to which they may become subject
under the Act, the Exchange Act or otherwise, arising from information furnished by or on behalf of such Holders, or their successors
or assigns, in writing, for specific inclusion in such registration statement or arising from any omission or the alleged omission
to state a material fact required to be stated therein or necessary to make the statement contained therein not misleading in connection
with the registration of the Registrable Securities, to the same extent and with the same effect as the provisions contained in
Section 5 of the Underwriting Agreement pursuant to which the underwriters have agreed to indemnify the Company.


 


5.3.2 Exercise of Purchase Option.
Nothing contained in this Purchase Option shall be construed as requiring the Holder(s) to exercise their Purchase Option or Warrants
underlying such Purchase Option prior to or after the initial filing of any registration statement or the effectiveness thereof.


 


5.3.3 Documents Delivered to Holders.
The Company shall furnish Chardan, as representative of the Holders participating in any of the foregoing offerings, a signed counterpart,
addressed to the participating Holders, of (i) an opinion of counsel to the Company, dated the effective date of such registration
statement (and, if such registration includes an underwritten public offering, an opinion dated the date of the closing under any
underwriting agreement related thereto), and (ii) a “cold comfort” letter dated the effective date of such registration
statement (and, if such registration includes an underwritten public offering, a letter dated the date of the closing under the
underwriting agreement) signed by the independent public accountants who have issued a report on the Company’s financial
statements included in such registration statement, in each case covering substantially the same matters with respect to such registration
statement (and the prospectus included therein) and, in the case of such accountants’ letter, with respect to events subsequent
to the date of such financial statements, as are customarily covered in opinions of issuer’s counsel and in accountants’
letters delivered to underwriters in underwritten public offerings of securities. The Company shall also deliver promptly to Chardan,
as representative of the Holders participating in the offering, the correspondence and memoranda described below and copies of
all correspondence between the Commission and the Company, its counsel or auditors and all memoranda relating to discussions with
the Commission or its staff with respect to the registration statement and permit Chardan, as representative of the Holders, to
do such investigation, upon reasonable advance notice, with respect to information contained in or omitted from the registration
statement as it deems reasonably necessary to comply with applicable securities laws or rules of FINRA. Such investigation shall
include access to books, records and properties and opportunities to discuss the business of the Company with its officers and
independent auditors, all to such reasonable extent and at such reasonable times and as often as Chardan, as representative of
the Holders, shall reasonably request. The Company shall not be required to disclose any confidential information or other records
to Chardan, as representative of the Holders, or to any other person, until and unless such persons shall have entered into reasonable
confidentiality agreements (in form and substance reasonably satisfactory to the Company), with the Company with respect thereto.


 




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5.3.4 Underwriting Agreement. The Company
shall enter into an underwriting agreement with the managing underwriter(s), if any, selected by any Holders whose Registrable
Securities are being registered pursuant to this Section 5, which managing underwriter shall be reasonably acceptable to the Company.
Such agreement shall be reasonably satisfactory in form and substance to the Company, each Holder and such managing underwriters,
and shall contain such representations, warranties and covenants by the Company and such other terms as are customarily contained
in agreements of that type used by the managing underwriter. The Holders shall be parties to any underwriting agreement relating
to an underwritten sale of their Registrable Securities and may, at their option, require that any or all the representations,
warranties and covenants of the Company to or for the benefit of such underwriters shall also be made to and for the benefit of
such Holders. Such Holders shall not be required to make any representations or warranties to or agreements with the Company or
the underwriters except as they may relate to such Holders and their intended methods of distribution. Such Holders, however, shall
agree to such covenants and indemnification and contribution obligations for selling shareholders as are customarily contained
in agreements of that type used by the managing underwriter. Further, such Holders shall execute appropriate custody agreements
and otherwise cooperate fully in the preparation of the registration statement and other documents relating to any offering in
which they include securities pursuant to this Section 5. Each Holder shall also furnish to the Company such information regarding
itself, the Registrable Securities held by it, and the intended method of disposition of such securities as shall be reasonably
required to effect the registration of the Registrable Securities.


 


5.3.5 Rule 144 Sale. Notwithstanding
anything contained in this Section 5 to the contrary, the Company shall have no obligation pursuant to Sections 5.1
or 5.2 to use its best efforts to obtain the registration of Registrable Securities held by any Holder (i) where such Holder
would then be entitled to sell under Rule 144 within any three-month period (or such other period prescribed under Rule 144 as
may be provided by amendment thereof) all of the Registrable Securities then held by such Holder, or (ii) where the number of Registrable
Securities held by such Holder is within the volume limitations under paragraph (e) of Rule 144 (calculated as if such Holder were
an affiliate within the meaning of Rule 144).


 


5.3.6 Supplemental Prospectus. Each
Holder agrees, that upon receipt of any notice from the Company of the happening of any event as a result of which the prospectus
included in the registration statement, as then in effect, includes an untrue statement of a material fact or omits to state a
material fact required to be stated therein or necessary to make the statements therein not misleading in light of the circumstances
then existing, such Holder will immediately discontinue disposition of Registrable Securities pursuant to the registration statement
covering such Registrable Securities until such Holder’s receipt of the copies of a supplemental or amended prospectus, and,
if so desired by the Company, such Holder shall deliver to the Company (at the expense of the Company) or destroy (and deliver
to the Company a certificate of such destruction) all copies, other than permanent file copies then in such Holder’s possession,
of the prospectus covering such Registrable Securities current at the time of receipt of such notice.


 


6.
ADJUSTMENTS.


 


6.1 Adjustments to Exercise Price and
Number of Securities. The Exercise Price and the number of Units underlying the Purchase Option shall be subject to adjustment
from time to time as hereinafter set forth:


 




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6.1.1 Stock Dividends - Split-Ups.
If after the date hereof, and subject to the provisions of Section 6.3 below, the number of outstanding Shares is increased
by a stock dividend payable in Shares or by a split-up of Shares or other similar event, then, on the effective date thereof, the
number of Shares underlying each of the Units purchasable hereunder shall be increased in proportion to such increase in outstanding
shares. In such case, the number of Shares, and the exercise price applicable thereto, underlying the Warrants underlying each
of the Units purchasable hereunder shall be adjusted in accordance with the terms of the Warrants.


 


6.1.2 Aggregation of Shares. If after
the date hereof, and subject to the provisions of Section 6.3, the number of outstanding Shares is decreased by a consolidation,
combination or reclassification of Shares or other similar event, then, on the effective date thereof, the number of Shares underlying
each of the Units purchasable hereunder shall be decreased in proportion to such decrease in outstanding shares and the Exercise
Price shall be proportionately increased. In such case, the number of Shares, and the exercise price applicable thereto, underlying
the Warrants underlying each of the Units purchasable hereunder shall be adjusted in accordance with the terms of the Warrants.


 


6.1.3 Replacement of Securities upon Reorganization,
etc. In case of any reclassification or reorganization of the outstanding Shares other than a change covered by Section
6.1.1 or 6.1.2 hereof or that solely affects the par value of such Shares, or in the case of any merger or consolidation
of the Company with or into another company (other than a consolidation or merger in which the Company is the continuing entity
and that does not result in any reclassification or reorganization of the outstanding Shares), or in the case of any sale or conveyance
to another company or entity of the property of the Company as an entirety or substantially as an entirety in connection with which
the Company is dissolved, the Holder of this Purchase Option shall have the right thereafter (until the expiration of the right
of exercise of this Purchase Option) to receive upon the exercise hereof, for the same aggregate Exercise Price payable hereunder
immediately prior to such event, the kind and amount of shares or other securities or property (including cash) receivable upon
such reclassification, reorganization, merger or consolidation, or upon a dissolution following any such sale or transfer, by a
Holder of the number of Shares of the Company obtainable upon exercise of this Purchase Option and the underlying Warrants immediately
prior to such event; and if any reclassification also results in a change in Shares covered by Section 6.1.1 or 6.1.2,
then such adjustment shall be made pursuant to Sections 6.1.1, 6.1.2 and this Section 6.1.3. The provisions
of this Section 6.1.3 shall similarly apply to successive reclassifications, reorganizations, mergers or consolidations,
sales or other transfers.


 


6.1.4 Changes in Form of Purchase Option.
This form of Purchase Option need not be changed because of any change pursuant to this Section, and a Purchase Option issued after
such change may state the same Exercise Price and the same number of Units as are stated in the Purchase Option as initially issued.
The acceptance by any Holder of the issuance of a new Purchase Option reflecting a required or permissive change shall not be deemed
to waive any rights to an adjustment occurring after the Commencement Date or the computation thereof.


 


6.2 Substitute Purchase Option. In
case of any consolidation of the Company with, or merger of the Company with, or merger of the Company into, another entity (other
than a consolidation or merger which does not result in any reclassification or change of the outstanding Shares), the entity formed
by such consolidation or merger shall execute and deliver to the Holder a supplemental Purchase Option providing that the holder
of each Purchase Option then outstanding or to be outstanding shall have the right thereafter (until the stated expiration of such
Purchase Option) to receive, upon exercise of such Purchase Option, the kind and amount of shares and other securities and property
receivable upon such consolidation or merger, by a holder of the number of Shares of the Company for which such Purchase Option
might have been exercised immediately prior to such consolidation, merger, sale or transfer. Such supplemental Purchase Option
shall provide for adjustments which shall be identical to the adjustments provided in Section 6. The above provision of
this Section shall similarly apply to successive consolidations or mergers.


 


6.3 Elimination of Fractional Interests.
The Company shall not be required to issue certificates representing fractions of Shares or Warrants upon the exercise of the Purchase
Option, nor shall it be required to issue scrip or pay cash in lieu of any fractional interests, it being the intent of the parties
that all fractional interests shall be eliminated by rounding any fraction up to the nearest whole number of Warrants, Rights,
Shares or other securities, properties or rights (or as otherwise provided pursuant to the Warrant Agreement or Rights Agreement,
as the case may be).


 




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7. RESERVATION AND
LISTING. The Company shall at all times reserve and keep available out of its authorized but unissued Shares, solely
for the purpose of issuance upon exercise of the Purchase Option or the Warrants or Rights underlying the Purchase Option, such
number of Shares or other securities, properties or rights as shall be issuable upon the exercise thereof. The Company covenants
and agrees that, upon exercise of the Purchase Option and payment of the Exercise Price therefor, all Shares and other securities
issuable upon such exercise shall be duly and validly issued, fully paid and non-assessable and not subject to preemptive rights
of any shareholder. The Company further covenants and agrees that upon conversion of the Rights or exercise of the Warrants underlying
the Purchase Option and payment of the respective Warrant exercise price therefor, all Shares and other securities issuable upon
such exercise shall be duly and validly issued, fully paid and non-assessable and not subject to preemptive rights of any shareholders.
As long as the Purchase Option shall be outstanding, the Company shall use its best efforts to cause all (i) Units and Shares issuable
upon exercise of the Purchase Option, (ii) Warrants issuable upon exercise of the Purchase Option (iii) Shares issuable upon exercise
of the Warrants included in the Units issuable upon exercise of the Purchase Option, (iv) Rights issuable upon exercise of the
Purchase Option and (v) Shares underlying the Rights included in the Units issuable upon exercise of the Purchase Option to be
listed and/or quoted (subject to official notice of issuance) on all securities exchanges (or, if applicable, on the OTC Bulletin
Board or OTC Markets Group, Inc. or any successor trading market) on which the Units, Shares, Rights or Warrants may then be listed
and/or quoted.


 


8.
CERTAIN NOTICE REQUIREMENTS.


 


8.1 Holder’s Right to Receive Notice.
Nothing herein shall be construed as conferring upon the Holders the right to vote or consent as a shareholders for the election
of directors or any other matter, or as having any rights whatsoever as a shareholders of the Company. If, however, at any time
prior to the expiration of the Purchase Option and its exercise, any of the events described in Section 8.2 shall occur,
then, in each such event, the Company shall give written notice of such event at least fifteen days prior to the date fixed as
a record date or the date of closing the transfer books for the determination of the shareholders entitled to such dividend, distribution,
conversion or exchange of securities or subscription rights, or entitled to vote on such proposed dissolution, liquidation, winding
up or sale. Such notice shall specify such record date or the date of the closing of the transfer books, as the case may be. Notwithstanding
the foregoing, the Company shall deliver to each Holder a copy of each notice given to the other shareholders of the Company at
the same time and in the same manner that such notice is given to the shareholders.


 


8.2 Events Requiring Notice. The
Company shall be required to give the notice described in this Section 8 upon one or more of the following events: (i) if the Company
shall take a record of the holders of its Shares for the purpose of entitling them to receive a dividend or distribution payable
otherwise than in cash, or a cash dividend or distribution payable otherwise than out of retained earnings, as indicated by the
accounting treatment of such dividend or distribution on the books of the Company, or (ii) the Company shall offer to all the holders
of its Shares any additional shares of capital stock of the Company or securities convertible into or exchangeable for shares of
capital stock of the Company, or any option, right or warrant to subscribe therefor, or (iii) a dissolution, liquidation or winding
up of the Company (other than in connection with a consolidation or merger) or a sale of all or substantially all of its property,
assets and business shall be proposed.


 


8.3 Notice of Change in Exercise Price.
The Company shall, promptly after an event requiring a change in the Exercise Price pursuant to Section 6 hereof, send notice to
the Holders of such event and change (“Price Notice”). The Price Notice shall describe the event causing
the change and the method of calculating same and shall be certified as being true and accurate by the Company’s Chief Executive
Officer.


 


8.4 Transmittal of Notices. All notices,
requests, consents and other communications under this Purchase Option shall be in writing and shall be deemed to have been duly
made when hand delivered, or mailed by express mail or private courier service: (i) if to the registered Holder of the Purchase
Option, to the address of such Holder as shown on the books of the Company, or (ii) if to the Company, to the following address
or to such other address as the Company may designate by notice to the Holders:


 




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Orisun Acquisition Corp.


555 Madison Avenue, Room 543


New York, NY 10022


Attn: Wei Chen


Telephone: (631) 220-3541


 


9.
MISCELLANEOUS.


 


9.1 Amendment The Company and Chardan
may from time to time supplement or amend this Purchase Option without the approval of any of the Holders in order to cure any
ambiguity, to correct or supplement any provision contained herein that may be defective or inconsistent with any other provisions
herein, or to make any other provisions in regard to matters or questions arising hereunder that the Company and Chardan may deem
necessary or desirable and that the Company and Chardan deem shall not adversely affect the interest of the Holders. All other
modifications or amendments shall require the written consent of and be signed by the party against whom enforcement of the modification
or amendment is sought.


 


9.2 Headings. The headings contained
herein are for the sole purpose of convenience of reference, and shall not in any way limit or affect the meaning or interpretation
of any of the terms or provisions of this Purchase Option.


 


9.3 Entire Agreement. This Purchase
Option (together with the other agreements and documents being delivered pursuant to or in connection with this Purchase Option)
constitutes the entire agreement of the parties hereto with respect to the subject matter hereof, and supersedes all prior agreements
and understandings of the parties, oral and written, with respect to the subject matter hereof.


 


9.4 Binding Effect. This Purchase
Option shall inure solely to the benefit of and shall be binding upon the Holder and the Company and their permitted assignees,
respective successors, legal representative and assigns, and no other person shall have or be construed to have any legal or equitable
right, remedy or claim under or in respect of or by virtue of this Purchase Option or any provisions herein contained.


 


9.5 Governing Law; Submission to Jurisdiction.
This Purchase Option shall be governed by and construed and enforced in accordance with the laws of the State of New York, without
giving effect to conflict of laws principles thereof. Each of the Holder and the Company hereby agrees that any action, proceeding
or claim against it arising out of, or relating in any way to this Purchase Option shall be brought and enforced in the New York
Supreme Court, County of New York, or in the United States District Court for the Southern District of New York, and irrevocably
submits to such jurisdiction, which jurisdiction shall be exclusive. Each of the Holder and the Company hereby waives any objection
to such exclusive jurisdiction and that such courts represent an inconvenient forum. Any process or summons to be served upon the
Company may be served by transmitting a copy thereof by registered or certified mail, return receipt requested, postage prepaid,
addressed to it at the address set forth in Section 8.4 hereof. Such mailing shall be deemed personal service and shall
be legal and binding upon the Company in any action, proceeding or claim. The Company and the Holder agree that the prevailing
party(ies) in any such action shall be entitled to recover from the other party(ies) all of its reasonable attorneys’ fees
and expenses relating to such action or proceeding and/or incurred in connection with the preparation therefore.


 


9.6 Waiver, Etc. The failure of the
Company or the Holder to at any time enforce any of the provisions of this Purchase Option shall not be deemed or construed to
be a waiver of any such provision, nor to in any way affect the validity of this Purchase Option or any provision hereof or the
right of the Company or any Holder to thereafter enforce each and every provision of this Purchase Option. No waiver of any breach,
non-compliance or non-fulfillment of any of the provisions of this Purchase Option shall be effective unless set forth in a written
instrument executed by the party or parties against whom or which enforcement of such waiver is sought; and no waiver of any such
breach, non-compliance or non- fulfillment shall be construed or deemed to be a waiver of any other or subsequent breach or non-compliance.


 


9.7 Execution in Counterparts. This
Purchase Option may be executed in one or more counterparts, and by the different parties hereto in separate counterparts, each
of which shall be deemed to be an original, but all of which taken together shall constitute one and the same agreement, and shall
become effective when one or more counterparts has been signed by each of the parties hereto and delivered to each of the other
parties hereto.


 




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9.8 Exchange Agreement. As a condition
of the Holder’s receipt and acceptance of this Purchase Option, Holder agrees that, at any time prior to the complete exercise
of this Purchase Option by Holder, if the Company and Chardan enter into an agreement (“Exchange Agreement”)
pursuant to which they agree that all outstanding Purchase Options will be exchanged for securities or cash or a combination of
both, then Holder shall agree to such exchange and become a party to the Exchange Agreement.


 


[Signature Page Follows]


 




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IN WITNESS WHEREOF, the Company has caused this Purchase Option
to be signed by its duly authorized officer as of the 6th day of August, 2019.


 


	 	ORISUN ACQUISITION CORP.
	 	 
	 	By:	/s/
    Wei Chen
	 	 	Name: Wei Chen
	 	 	Title: Chief Executive Officer


 




     


     


    

 


Form to be used to exercise Purchase Option


 


Orisun Acquisition Corp.


555 Madison Avenue, Room 543


New York, NY 10022


 


Date:_________________, 20___


 


The undersigned hereby elects irrevocably
to exercise all or a portion of the within Purchase Option and to purchase ____ Units of Orisun Acquisition Corp. and hereby makes
payment of $____________ (at the rate of $_________ per Unit) in payment of the Exercise Price pursuant thereto. Please issue the
securities as to which this Purchase Option is exercised in accordance with the instructions given below.


 


or


 


The undersigned hereby elects irrevocably
to convert its right to purchase _________ Units purchasable under the within Purchase Option by surrender of the unexercised portion
of the attached Purchase Option (with a “Value” based of $_______ based on a “Market Price” of $_______).
Please issue the securities comprising the Units as to which this Purchase Option is exercised in accordance with the instructions
given below.


 


NOTICE: The signature to this assignment
must correspond with the name as written upon the face of the purchase option in every particular, without alteration or enlargement
or any change whatever


 


Signature(s) Guaranteed:


 


THE SIGNATURE(S) SHOULD BE GUARANTEED BY
AN ELIGIBLE GUARANTOR INSTITUTION (BANKS, STOCKBROKERS, SAVINGS AND LOAN ASSOCIATIONS AND CREDIT UNIONS WITH MEMBERSHIP IN AN APPROVED
SIGNATURE GUARANTEE MEDALLION PROGRAM, PURSUANT TO S.E.C. RULE 17Ad-15).


 


INSTRUCTIONS FOR REGISTRATION OF SECURITIES


 


Name


	 
	(Print in Block Letters)
	
         

        Address

         



 




     


     


    

 


Form to be used to assign Purchase Option:


 


ASSIGNMENT


 


(To be executed by the registered Holder
to effect a transfer of the within Purchase Option):


 


FOR VALUE RECEIVED,______________________________________________
does hereby sell, assign and transfer unto___________________________________________ the right to purchase __________ Units of
Orisun Acquisition Corp.. (“Company”) evidenced by the within Purchase Option and does hereby authorize
the Company to transfer such right on the books of the Company.


 


Dated:___________________, 20___


 


	 	 
	 	Signature


 


	 	 	 
	 	NOTICE: The signature to this assignment must correspond with the name as written upon the face of the purchase option in every particular, without alteration or enlargement or any change whatever.
	 	 


Signature(s) Guaranteed:


	 


THE SIGNATURE(S) SHOULD
BE GUARANTEED BY AN ELIGIBLE GUARANTOR INSTITUTION (BANKS, STOCKBROKERS, SAVINGS AND LOAN ASSOCIATIONS AND CREDIT UNIONS WITH
MEMBERSHIP IN AN APPROVED SIGNATURE GUARANTEE MEDALLION PROGRAM, PURSUANT TO S.E.C. RULE 17Ad-15).