Bandgap Engineering through Halide Double‐Perovskite Alloys: A High‐Throughput First‐Principles Study

Halide double perovskites are a new category of semiconductors that have shown promising optoelectronic properties. Their performance can be further improved by band engineering through alloying. Herein, based on the previous high‐throughput first‐principles study that predicts 118 thermodynamically stable halide double perovskites, 273 halide double‐perovskite pairs with lattice mismatch less than 1% and bandgap difference larger than 0.5 eV are filtered. Low lattice mismatch favors high miscibility and coherent interfaces if made into heterostructures, and large‐bandgap difference means wide tuning range. Further study on bandgap alignments shows that almost all halide double‐perovskite pairs show type‐I alignment, which favors high photoluminescence quantum yield (PLQY) if made into heterostructures. The study not only provides a list of candidate halide double‐perovskite alloys for wide‐range bandgap engineering and heterostructures with coherent interfaces, but also gives insights into developing new optoelectronic materials based on halide double perovskites and their alloys.