Tempelaar develops theory and simulation methods (surface-hopping and vibronic exciton models) for two-dimensional electronic spectroscopy, explaining how vibronic coupling sustains excitonic coherence in photosynthetic light-harvesting complexes such as the Fenna-Matthews-Olson complex and LH2, and extending these ideas to singlet fission and organic-semiconductor aggregates. He is a faculty affiliate of Northwestern's Institute for Quantum Information Research and Engineering (INQUIRE).