Abstract
AbstractLead‐free Cs2AgInCl6 and Cs2AgInBr6 double perovskites are studied by a combination of advanced ab‐initio calculations and photoluminescence experiments. We show that they are insulators with direct band gaps of 2.53 and 1.17 eV, respectively; most importantly, they are characterized by unusually low absorption rates in a ~1 eV wide energy region above the band gap, caused by rather peculiar electronic properties. Consequently, this low absorption conveys very long recombination lifetimes, up to milliseconds at low temperature. Our theoretical analysis suggests that such materials can achieve a good compromise between photoconversion efficiency (above 10%) and visible transmittance (above 30%), which makes them potentially suited for lead‐free semitransparent solar cell applications.image
Highlights
The replacement of the harmful lead (Pb) in lead halide perovskites for efficient, yet low cost solar cells and LEDs1-5 is one of the most pressing issues in todays' materials science
We focus on two interesting double perovskites, featuring the Ag/In combination at the B site, namely Cs2AgInCl6 (CAIC) and Cs2AgInBr6 (CAIB); they can be seen as the reference end-points of a mixed CAI (C/B) series which encompasses a range of uncommon fundamental properties, and have the potential to become the building blocks of a novel stream of lead-free photovoltaic and nanophotonic applications
CAIC was recently put in the spotlight by its reportedly efficient warm-white light emission.[67]. This compound is characterized by a direct band gap, and quite peculiar absorption and photoluminescence properties which, despite several studies already present in literature,[61,62,63,64,65,66,67,68] are in our opinion not yet well clarified, leaving room to substantial uncertainties and speculations; it is sufficient to say that band gap values ranging from 1 to 3.67 eV were reported, according to the specific type of calculation
Summary
The replacement of the harmful lead (Pb) in lead halide perovskites for efficient, yet low cost solar cells and LEDs1-5 is one of the most pressing issues in todays' materials science.
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