The phrase "the place with no darkness" is actually introduced into this excellent novel in Chapter 2 at the very beginning, when Winston dreams of O'Brien, and is repeated at various other stages throughout the novel. The impact of this dream and phrase is to foreshadow the future that Winston Smith faces and how crucial a part O'Brien will play in that future, even though it is in a radically different way from what Winston imagined. Note how this phrase is introduced in Chapter 2:
Seven years it must be--he had dreamed that he was walking through a pitch-dark room. And someone sitting to one side of him had said as he passed: "We shall meet in the place where there is no darkness." ... It was O'Brien who had spoken to him out of the dark.
As the novel develops this association of the phrase with O'Brien is cemented more and more, so that when Winston finally reaches the Ministry of Love, and meets O'Brien there in a place with no darkness, he instantly feels that he recognises this place. This is one of many ways that Orwell foreshadows the future in this novel and points towards its rather grim and unrelenting close.