Lead-Free Halide Double Perovskite Cs2AgBiBr6 with Decreased Band Gap

• Environmentally friendly halide double perovskites with improved stability are regarded as a promising alternative to lead halide perovskites. The benchmark double perovskite, Cs2AgBiBr6, shows attractive optical and electronic features, making it promising for high-efficiency optoelectronic devices. However, the large band gap limits its further applications, especially for photovoltaics. Herein, we develop a novel crystal-engineering strategy to significantly decrease the band gap by approximately 0.26 eV, reaching the smallest reported band gap of 1.72 eV for Cs2AgBiBr6 under ambient conditions. The band-gap narrowing is confirmed by both absorption and photoluminescence measurements. Our first-principles calculations indicate that enhanced Ag/Bi disorder has a large impact on the band structure and decreases the band gap, providing a possible explanation of the observed band-gap narrowing effect. This work provides new insights for achieving lead-free double perovskites with suitable band gaps for optoelectronic applications. 

Ämnesord

NATURVETENSKAP  -- Kemi -- Materialkemi (hsv//swe)

NATURAL SCIENCES  -- Chemical Sciences -- Materials Chemistry (hsv//eng)

NATURVETENSKAP  -- Kemi -- Teoretisk kemi (hsv//swe)

NATURAL SCIENCES  -- Chemical Sciences -- Theoretical Chemistry (hsv//eng)

Nyckelord

Ag�Bi disorder

band-gap engineering

crystal engineering

Cs2AgBiBr6

lead-free double perovskites

Bismuth compounds

Bromine compounds

Calculations

Cesium compounds

Lead compounds

Optoelectronic devices

Perovskite

Silver compounds

Absorption and photoluminescence

Ambient conditions

Band gap narrowing

Double perovskites

First-principles calculation

Halide perovskites

High-efficiency

Optoelectronic applications

Energy gap

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