A radiation detector having an energy-integrating detection layer and at least one direct-conversion detection layer is described. In certain embodiments, the direct-conversion layer is impacted first by an incident X-ray beam, such that X-ray photons stopped at the direct-conversion layer are generally lower in energy than those which reach the energy-integrating detection layer. The data acquired using the direct-conversion layers and energy-integrating layers may be combined to provide additional spectral discrimination, such as in material decomposition or contrast-enhancement applications.