There can be few playwrights as devoted to the magic of live theatre as Ireland's garlanded Conor McPherson, author of acclaimed plays such as The Weir, Port Authority and Shining City. So it is a surprise to learn how strong a pull television now has on the writer.

On the eve of the transfer of the Donmar Theatre's triumphant revival of The Weir to a large West End venue, and following the feted Broadway opening of his latest play, The Night Alive, it is the prospect of writing adaptations for television that is now engaging arguably Ireland's greatest living playwright.

"More and more it seems like television is where all the creative work is happening," he told the Observer. "I am increasingly asked to write for TV, in fact. Years ago it would have been small movies, but there are fewer of those kind of movies being made now."

McPherson is already adapting a run of detective novels written by John Banville under the pseudonym Benjamin Black. The BBC1 series, Quirke, will star Gabriel Byrne in the title role and is being developed with the veteran TV screenwriter Andrew Davies. "It is such a different format to learn," said McPherson. "But box-set television has created a new art form. People really settle down for an hour or so of viewing now."

The playwright's love of historical settings, as seen in the National Theatre's production of The Veil, is also drawing him towards Anthony Trollope. The prolific Victorian wrote four novels set in Ireland, including Phineas Finn, which McPherson especially admires. Written in 1896, it tells of the struggles of a young Irish MP and McPherson is intrigued by the way it shows how politicians shore up their moral standing.

"I love period work, so television adaptations would be the thing for me. It would be attractive, but I would want to do something in four or six parts, not open-ended."

McPherson is not turning his back on the stage, which remains a constant passion: "It would make me miserable not to write for theatre again. My friend, the actor Jim Norton, says: 'Follow your bliss!' and happily my plays have looked after me and so I'm not desperately looking for a payday. I can make a living."

McPherson says he has worked with stage actors since his teens and is still beguiled by what they do: "What is written on the page is never the most important thing. It is a question of what the actors bring to it."

He believes an audience can connect with the mysteries of life in a theatre. "It's like a religious ceremony if it's good. It has the same structure as that sort of ritual. I try to take that energy and push it into the darkness, into the mysterious."

It is theatre that still grips him most: "I would say that a good play almost comes and writes you. You are scribbling notes, but where does it come from when you are inspired? I have talked to other playwrights like Jez Butterworth about this and we are all bewildered. But I hope to God I get more of those ideas that don't leave you alone."

All the same, he admitted it is difficult to get new work into big London theatres: "The West End, I think, is in thrall to celebrity culture. They need a star, and stars are difficult to entice into a new play. It is quite a risk. The National Theatre is the exception."

The warm critical reception in America for The Night Alive (Ben Brantley of the New York Times called it "extraordinary", with "something bright and beautiful pulsing in its shadows") means that McPherson, who also directed the production, has extra bounce in his step.

"The great thing was taking the entire Donmar cast to New York. That made it even more enjoyable," he said. "We haven't really changed it for all the Americans sitting out there watching in the dark. I flatter myself, of course, that my plays go over well there because they have such good taste. Less flatteringly, one might also say they see it through the prism of an idea of Irishness.

You can't argue with that. We should "be very proud. I would like to say the demand for our actors is to do with our high standards of training. American actors tend to base more on their feelings, while British actors tend to think about it much more as a job."

As London audiences await the reopening of The Weir at Wyndhams theatre next week, the playwright has no clear explanation for its success. "The one person who can never actually see it is me," he said. "I wrote it in 1997 and ever since then it has been owned by other people. Audiences just like being in that bar, I think."

His preoccupations with spirits, spectres and secrets are a symptom, he said, of the dual theatrical traditions in Britain and Ireland: "British theatre tends to look at society, and perhaps at politics, in a horizontal way. It flows from the tradition of empiricist thinking, from Locke and Hume, from taking what you see in front of you and investigating it."

In Ireland, he suggested, there is a mystical tradition: "We live on islands so close to each other yet our cultural psyches are so different. Irish plays often ask more vertical questions, like why are we here, where are we going? This is not just me making some kind of pronouncement, it is there in the work you see. If you compare the plays of Sebastian Barry with those of David Hare, you can see it, yet they are both equally powerful."

For McPherson the distinction is not reductive, since any worthy playwright will push at all the boundaries, no matter which side of the Irish Sea they were born: "If you write good plays, you ask more questions than provide answers."