Microelectronic assemblies, and related devices and methods, are disclosed herein. For example, in some embodiments, a microelectronic assembly may include a die having a front side and a back side, the die comprising a first material and conductive contacts at the front side; and a thermal layer attached to the back side of the die, the thermal layer comprising a second material and a conductive pathway, wherein the conductive pathway extends from a front side of the thermal layer to a back side of the thermal layer.