Fluorescence detected two-dimensional spectroscopy is a powerful technique that can probe the effects of electronic and vibrational coherences in molecules and molecular aggregates on the external signals. As functionality of systems such as organic light emitting diodes or solar cells depend on the long-lived external signals that include fluorescence and photocurrent, the technique provides a detailed information about the role of coherences on the functioning of the devices. In fact, this unique technique promises to initiate new directions in experiments which enable us to utilize quantum properties of matter in useful devices. However, some challenges in interpreting the results of the measurements have persisted. The main difficulty has been in isolating the nonlinear signals induced by the ultrafast coherences from other nonlinear signals contributed by long lived incoherent processes. A detailed theoretical analysis has shown that it is possible to differentiate the two types of signals by analyzing the phases. In this project, we aim to experimentally test the theoretical prediction and carry out detailed experiments on molecules and molecular aggregates that can be used in LEDs and solar cells.