PHYSICS AND CHEMISTRY OF DEFECT-TOLERANT PEROVSKITE MATERIALS: CONTROLLING CARRIER DYNAMICS, ION MIGRATION, AND INTERFACIAL RECOMBINATION FOR STABLE OPTOELECTRONICS

Abstract

Halide perovskite semiconductors have become important materials for optoelectronics. These materials can convert power with efficiency over 26 percent. This is impressive because they are made at temperatures. Low temperature processing creates a lot of defects. The number of defects ranges from 10¹¹ to 10¹⁶ per centimeter. This situation is called a paradox. It is known as "defect tolerance." It happens because of the way the electrons are arranged in these materials. The band-edge orbital symmetry is inverted. The valence band maxima are antibonding. The dielectric screening is strong. All of these factors make the natural point defects not harmful. This review looks closely at the physics and chemistry behind defect tolerance in AMX₃ perovskites. It studies how point defects form and the energy needed for that. It also looks at how the lattice moves and how polarons form. These help to hide charged defects. The review examines how carriers recombine. This happens through bimolecular and Auger processes. The review classifies the natural point defects. It separates the ones that are harmless from the deep ones that cause problems. These deep ones are called -radiative killer centers. The review looks at how ions move. This movement happens because of energy needed. The energy ranges from 0.2 to 0.8 electron volts. The review also studies how the materials break down. This includes electric field screening, phase decomposition at interfaces and halide segregation from light. To fix these problems the review looks at solutions. These include making the materials thinner and using dual-phase engineering. A special focus is on self-assembled monolayers. These layers help protect the interface in perovskite solar cells. Carbazole-based monolayers, like 2PACz derivatives and co-assembly methods work well. They reduce the -radiative recombination at the interface. The best devices keep than 93 percent of their original efficiency after 1,000 hours. This review connects defect physics with real-world interface engineering. It gives a plan for making perovskite optoelectronics for use, in the market.