Uncovering Transport Mechanisms in Perovskite Materials and Devices with Recombination-Induced Action Spectroscopies

Although valuable insights are derived from conventional spectroscopic approaches, the understanding of a photovoltaic device's operation mechanisms can be limited in ex situ measurements. For example, the signals measured in transient absorption experiments reflect the concentrations and extinction coefficients of all photoexcited species in a material regardless of functional relevance. Elimination of such ambiguities has motivated the development of various action spectroscopy techniques in which the response of a photovoltaic device to a sequence of laser pulses is directly detected. The class of action spectroscopies described in this Perspective leverages recombination-induced nonlinearities to distinguish lossy (fluorescence) and productive (photocurrent) processes within the active layers of photovoltaic cells. Although recombination processes are problematic in alternate approaches for conducting action spectroscopies, our experiments show that this type of nonlinearity can be exploited to reveal transport mechanisms on nanosecond time scales. Applications to mixtures of layered perovskite quantum wells are presented to demonstrate signatures of energy funneling and longrange carrier drift in photovoltaic devices.

Automated summary

Conventional spectroscopic approaches have limitations in understanding the operation mechanisms of photovoltaic devices. Various action spectroscopy techniques have been developed to overcome these limitations and directly detect the response of photovoltaic devices to laser pulses. This Perspective focuses on a class of action spectroscopies that utilize recombination-induced nonlinearities to distinguish lossy and productive processes in photovoltaic cells. The experiments presented in this Perspective demonstrate the potential of using this nonlinearity to reveal transport mechanisms on nanosecond timescales in photovoltaic devices.