A pinboard by
Qingdong Ou

PhD student, Monash University


Metal halide perovskites are an emerging class of layered semiconductors with unique electronic and optical properties that allow for low-cost, highly efficient optoelectronic applications, including photovoltaics, light-emitting diodes (LEDs), photodetectors and solar-to-fuel energy conversion devices. The power conversion efficiency of perovskite solar cells has quickly risen to 22.1% over the past six years. Their high optical emission efficiency makes these perovskites suitable for use in optoelectronic and photonic devices, such as LEDs, photodetectors, waveguides and lasers. For instance, perovskite LEDs have achieved external quantum efficiency over 11%, which is already comparable to that of state-of-the-art organic LEDs. Photodetectors based on planar perovskite films exhibit high gain, fast response time and good flexibility, showing great promise as next-generation highly efficient photodetectors. Perovskites are also considered to be a class of layered materials, whose optical properties can be controlled by varying the number of layers (thickness), particularly at thicknesses lower than their exciton Bohr radius (~few nanometres). It has been known that the rapid progress in graphene has led to exploration of many two-dimensional (2D) materials such as hexagonal boron nitride, transition metal dichalcogenides and black phosphorus, etc. In particular, 2D semiconductor materials are of huge benefit due to strong in-plane quantum confinement and sizable bandgap, which are desired for many optoelectronic applications. Compared with conventional 2D materials that are covalent semiconductors, 2D perovskites are ionic materials, giving them special properties of their own. 2D perovskites can exhibit enhanced fluorescence emission decay rates and higher exciton binding energies compared with their bulk counterparts. In addition, the large surface area of 2D sheets enables stronger interaction with other 2D materials for efficient energy transfer. Controlling of the electronic characteristics of 2D perovskite semiconductors is thus of great importance for future low-energy electronics technology.