Excited State Properties of Hybrid Perovskites

• DOI: 10.1021/acs.accounts.5b00445
• Publication Date: 2015-12-22T14:17:22Z
• Authors: Michele Saba; Francesco Quochi; Andrea Mura; Giovanni Bongiovanni
• Keywords: 01 natural sciences; 7. Clean energy; 0104 chemical sciences

ConspectusMetal halide perovskites have come to the attention of scientific community for progress achieved in solar light conversion. Energy sustainability is one priorities our society, and materials advancements resulting low-cost but efficient cells large-area lighting devices represent a major goal applied research. From basic point view, are an exotic class hybrid combining some merits organic inorganic semiconductors: large optical absorption, mobilities, tunable band gap together with possibility be processed solution. When novel promising semiconductors comes into limelight, lively discussions ensue on photophysics band-edge excitations, because just states close edge entailed energy/charge transport emission. This was case several decades ago III–V semiconductors, it has been up 10 years organics, currently perovskites.Our aim this Account rationalize body experimental evidence perovskite coherent theoretical framework, borrowing from knowledge acquired over optoelectronics. A crucial question whether photon absorption leads population unbound, conductive free charges or instead excitons, neutral insulating bound created by Coulomb interaction below energy gap. We first focus estimates exciton binding (Eb): at room temperature, Eb comparable thermal kBT MAPbI3 increases values 2–3kBT wide MAPbBr3 MAPbCl3. Statistical considerations predict that these values, even though larger than energy, let carriers prevail excitons all levels excitation densities relevant devices. The analysis confirms behave as free-charge semiconductors. Thanks such property, combination energies covering entire spectrum, platform highly efficient, single multijunction cells. Concerning use color-tunable emitting devices, free-charges not preferred species, they recombine radiatively through bimolecular process inefficient charge-injection typical LED operation. Strategies overcome limit, thus extend beyond conversion, could borrowed semiconductor optoelectronics include fabrication nanostructures reduced dimensionality alter electronic density states, well engineering composite materials.