You may be in a tough spot. In order to file jointly, you must treat your spouse as a US resident for tax purposes, and that means reporting all their worldwide income and paying US tax on it. There is a deduction or credit for any taxes they paid in a foreign country that should offset some of the double-taxation problem, but I don't know that it will completely offset it. You may want to test your situation.
If you provide care in your home for a dependent child, and paid more than half the expenses, and your spouse did not live in your home in 2019, you can probably file as head of household and claim the solar credit without needing to report your spouse's income.
To treat your spouse as a US resident for tax purposes and file jointly, your spouse need an International Tax ID number (ITIN). You get this by filling out form W-7, the ITIN application, and attach the W-7 and any required proofs to your tax return, and mail it all to the address for W-7 processing. After the IRS issues the ITIN, they will process the tax return.
