HalogenidPerowskit

Halide perovskites, known in German as Halogenid-Perowskite, describe a class of crystalline materials with a general ABX3 composition. A is a monovalent cation such as formamidinium (FA+), methylammonium (MA+), or cesium (Cs+); B is typically lead (Pb2+), though tin (Sn2+) is investigated as a lead-free alternative; X is a halide, usually iodide, bromide, or chloride, often used in mixed-halide combinations to tune properties.

The compounds adopt the perovskite structure, consisting of corner-sharing BX6 octahedra that form a three-dimensional network. The A cations occupy spaces between the octahedra. Variants include layered two-dimensional or quasi-2D perovskites created with larger organic cations, which can improve moisture resistance but alter electronic properties. Mixed-dimensional hybrids, combining 2D and 3D layers, are also explored.

Halide perovskites exhibit strong direct bandgaps and high optical absorption, allowing very thin films to harvest light efficiently. The bandgap is highly tunable by halide composition, ranging roughly from 1.2 to 2.3 eV. They often show long carrier diffusion lengths and defect-tolerant electronic structures, and can be processed from solution, enabling relatively simple fabrication methods such as spin-coating or vapor-assisted deposition.

Applications span solar cells, light-emitting diodes, lasers, and photodetectors. In photovoltaics, lab-scale single-junction devices have surpassed about 25% efficiency, and tandem configurations with silicon are actively studied. Common device architectures include planar and mesoporous stacks, with performance aided by additives, mixed-cation/halide formulations, and encapsulation.

Key challenges are stability under moisture, heat, and light, and concerns about lead toxicity. Ongoing research focuses on improving environmental stability, developing lead-free alternatives, and establishing environmentally sound recycling and manufacturing practices.