Preheat the oven to 350°F (175°C). Grease a 9×5-inch loaf pan and line it with parchment paper, leaving an overhang on the sides for easy removal.
In a large bowl, whisk together the all-purpose flour, unsweetened cocoa powder, baking powder, baking soda, and salt until well combined.
In a separate medium bowl, beat the granulated sugar, light brown sugar, and eggs together until smooth and creamy.
Add the vegetable oil and vanilla extract to the sugar and egg mixture and whisk until fully incorporated.
Alternately add the dry ingredients and the buttermilk to the wet mixture, beginning and ending with the dry ingredients. Mix gently until just combined; do not overmix.
Fold in the semi-sweet chocolate chips evenly into the batter.
Pour the batter into the prepared loaf pan and smooth the top with a spatula.
Bake in the preheated oven for 45-50 minutes, or until a toothpick inserted into the center comes out with a few moist crumbs but no raw batter.
Remove the loaf from the oven and allow it to cool in the pan for 15 minutes.
Using the parchment paper overhang, lift the loaf out of the pan and transfer it to a wire rack to cool completely before slicing.