Preheat the oven to 350°F (175°C).
In a medium bowl, combine the chocolate graham cracker crumbs, cocoa powder, 1/4 cup SPLENDA® and melted butter until evenly moistened.
Press the crumb mixture firmly into the bottom and up the sides of a 9-inch pie plate to form a crust.
Bake the crust for 8 to 10 minutes, then remove and let it cool completely.
In a mixing bowl, beat the reduced-fat cream cheese, peanut butter, and ripe banana with an electric mixer until smooth and combined.
Beat in 1/3 cup SPLENDA® and taste; add an extra tablespoon or two of sweetener if desired for personal taste.
Gently fold the sugar-free whipped topping into the peanut butter mixture until evenly incorporated.
Transfer the filling into the cooled crust, smooth the top, and refrigerate for at least several hours until set before slicing and serving.