Defects Activity in Metal Halide Perovskites
Annamaria Petrozza a
a Istituto Italiano di Tecnologia, Via Morego, 30, Genova, Italy
Invited Speaker, Annamaria Petrozza, presentation 052
Publication date: 24th October 2023

Bandgap tuning is a crucial characteristic of metal-halide perovskites, with benchmark lead-iodide compounds having a bandgap of 1.6 eV. To increase the bandgap up to 2.0 eV a straightforward strategy is to partially substitute iodine with bromine in so-called mixed-halide lead perovskites. Such compounds are prone, however, to defect-induced halide segregation resulting in bandgap instabilities, which limits their application in tandem solar cells and a variety of optoelectronic devices. The optimization of the perovskite composition and surface passivating agents can effectively slow down, but not completely stop, such light-induced instabilities. Here I will show how we identify the defect and the relative intra-gap electronic state/charge carrier dynamics that triggers the material transformation and bandgap shift. It allows us to engineer the perovskite band edge energetics by engineering the chemical composition of the perovskite crystalline unit to radically deactivate the photo-activity of such electronic states and stabilize the perovskite bandgap over the entire spectral range above 1.6 eV. Overall, I will show how the photo-instability of lead based single and mixed halide perovskites, which can been seen as photo-degradation and bandgap photo-destabilization, has the same root. Then, I will conclude my lecture showing how, by halides alloying, we can achieve photo-stable bandgaps in a broad spectral range from NIR to 2 eV, in tin-based perovskites. Here, the defect chemistry modulates the electronic property of the semiconductor switching from a highly p-doped to an intrinsic one.


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