Structure-induced optoelectronic properties of phenothiazine-based materials

Phenothiazine (PTZ)-based materials have recently received considerable interest owing to their intriguing optoelectronic properties, low-cost, versatility of functionalization, and commercial availability. The advent of molecular engineering concepts in π-conjugated organic materials, such as the “donor-acceptor” approach, propelled the synthesis of a large number of PTZ-derivatives with tailored properties like low bandgap, tunable energy levels, and reversible redox properties. This resulted in the promising application of PTZs as electron donors or acceptors in organic solar cells or as hole-transporting materials in organic light-emitting diodes and perovskite solar cells. In this review, we discuss the recent and most appealing design strategies of PTZ-based materials for optoelectronics, with emphasis on the impact of the structural modifications on the fundamental physicochemical properties (absorption, emission, frontier energy levels, charge carrier mobility). We also highlight the key achievements in the development of solar cells, light-emitting diodes, and batteries employing PTZ core semiconductors. Our final goal is to underpin the reasons that still limit the performance of PTZ-based optoelectronics and to outline future research directions for the next-generation PTZ materials with ever enhanced properties.