Au-delà can be used in two ways, as a location adverb.

• au-delà de when the location is specified

  Il est interdit d’aller au-delà de la barrière (It’s forbidden to go beyond the fence)

• au-delà when the location is already known, and doesn’t have to be specified

  Tu peux aller jusqu’à la barrière, mais c’est interdit au-delà. (You can go as far as the fence, but it’s forgotten to go beyond.)

So in your example, the correct form is indeed au-delà de la simplicité matérielle.

See more examples in the Wiktionnaire.