FRANKFURT (Reuters) - Ailing solar company Q-Cells said it agreed a deal in principle with major bondholders to restructure its three convertible bonds, a move that could give the group more time to recover from the sector's crisis.

Q-Cells, once the world's largest maker of solar cells, said the agreement included a cash payment of 20 million euros ($26.2 million) to the holders of its convertible bond maturing this year.

Two bonds due in 2014 and 2015 will be restructured through a debt-to-equity swap, the Germany-based company added.

"Following this equitisation, the 2012, 2014 and 2015 bondholders shall collectively hold at least 95 percent of the issued share capital of Q-Cells SE," the company said on Wednesday.

Q-Cells said the agreement needs the approval of the bondholders, its shareholders and relevant authorities, adding it expects the restructuring measures to be put in place in the second half of this year.

Q-Cells last week said it would restructure two convertible bonds and was trying to agree a partial repayment of a third, as the German solar company struggles to secure financing following a sector shakeout that has forced some rivals out of business. ($1 = 0.7639 euros) (Reporting by Christoph Steitz; Editing by Erica Billingham)