The jobs of 161 workers at Romag, in Leadgate, near Consett, County Durham, were saved when Wearside housing developer Gentoo bought the company, which was facing a cash crisis, in April.
In January, Romag's shares were suspended from trading on the Stock Exchange after it emerged that ex-chairman John Kennair had made a £3.97m payment to help balance the books without informing the board.
In June Romag announced it would take on 20 more staff and install a third production line.
Yesterday the firm said work on the production line, costing more than £1m, had been completed and would treble its production capacity.
Romag said the investmnet demonstrated its commitment to the manufacturing plant here and the future of solar panel technology.