Related Experiment Video
Updated: Feb 2, 2026

Low Pressure Vapor-assisted Solution Process for Tunable Band Gap Pinhole-free Methylammonium Lead Halide Perovskite Films
Published on: September 8, 2017
Lead-Free Direct Band Gap Double-Perovskite Nanocrystals with Bright Dual-Color Emission
Bin Yang1, Xin Mao1, Feng Hong1
1University of the Chinese Academy of Sciences , Beijing 100049 , P.R. China.
Abstract:
Lead-free double-perovskite nanocrystals (NCs), that is, Cs2AgIn xBi1- xCl6 ( x = 0, 0.25, 0.5, 0.75, and 0.9), that can be tuned from indirect band gap ( x = 0, 0.25, and 0.5) to direct band gap ( x = 0.75 and 0.9) are designed. Direct band gap NCs exhibit 3 times greater absorption cross section, lower sub-band gap trap states, and >5 times photoluminescence quantum efficiency (PLQE) compared to those observed for indirect band gap NCs (Cs2AgBiCl6). A PLQE of 36.6% for direct band gap NCs is comparable to those observed for lead perovskite NCs in the violet region. Besides the band edge violet emission, the direct band gap NCs exhibit bright orange (570 nm) emission. Density functional theory calculations suggesting forbidden transition is responsible for the orange emission, which is supported by time-resolved PL and PL excitation spectra. The successful design of lead-free direct band gap perovskite NCs with superior optical properties opens the door for high-performance lead-free perovskite optoelectronic devices.
More Related Videos
Related Concept Videos
Band Theory
The energy difference between these bands is known as the band gap.
Conductor, Semiconductor,...
Colors and Magnetism
When atoms or molecules absorb light at the proper frequency, their electrons are excited to higher-energy orbitals. For many main group atoms and molecules, the absorbed photons are in the ultraviolet range of the electromagnetic spectrum, which cannot be detected by the human eye. For coordination compounds, the energy difference between the d orbitals often allows photons in the visible range to be absorbed and emitted, which is seen as colors by the human...
Fixing Double-strand Breaks
Emission Spectra
Gap Junctions
Gap Junctions

