Adyen's IPO will value the firm at $8.3 billion making it one Europe's biggest technology listings in recent times. : Adyen shares will begin trading on Wednesday in what will be one of Europe's largest technology initial public offerings (IPOs). But you'd be forgiven for not knowing much about the Dutch financial technology or fintech firm as it has flown under the radar for many years. Adyen was founded in 2006 in the Netherlands. Its current CEO, Pieter van der Does, was one of the co-founders.