Place orange juice in small saucepan over medium heat; cook and reduce to ¼ cup and cool. 

Melt chocolate over double boiler. 

Line baking sheet with parchment paper. Pour melted chocolate onto the parchment paper to ¼-inch thickness; swirl in the cooled orange juice reduction with a spatula, creating thin channels in the chocolate. 

Sprinkle orange peel and pistachios over chocolate; press into chocolate. 

Cool bark completely until chocolate hardens; break into pieces.