Lead-free double perovskite nanocrystals (NCs) of Cs2AgIn1–x Bi x Cl6 (x = 0, 0.05, 0.15, 0.3, 0.6, and 1) were synthesized with control over the size distribution. Detailed structural studies were carried out on the resulting double perovskite NCs to confirm the alloying and structural modification. Alloying of Bi leads to change in optical properties, such as the band gap, and enhancement in oscillator strength of first excitonic transition and the white light emission (WLE) properties. The band gap of the double perovskite NCs was estimated; a direct band gap transition value of ∼3.46 eV is obtained for pure Cs2AgInCl6 NCs. This value of the band gap has reduced with increase of Bi doping, which also leads a band gap transition from direct to indirect band gap. This system exhibits a sub-band gap emission between ∼570 and 620 nm along with band-edge emission, which is strongly dependent on the alloying concentration. A gamut of emission is observed in the alloyed systems. The Commission International de I’Eclairage (CIE) coordinates of (0.36, 0.35) for the 30% Bi-doped sample, with color rendering index values of ∼91, and correlated color temperature of 4443 with D uv of −0.0065 are observed, which are found to be very promising for WLE applications.

Recently, lead free all-inorganic double perovskites have revolutionized photovoltaic research, showing promising light emitting efficiency and tunability via modification of inherent structural and chemical properties. Here, we report a combined experimental and theoretical study on the variation of carrier–lattice interaction and optoelectronic properties of Cs2AgIn1–x Bi x Cl6 double perovskite nanocrystals with varying alloying concentrations. Our UV–vis study confirms the parity allowed first direct transition for x ≤ 0.25. Using a careful analysis of Raman spectra assisted with first-principles simulations, we assign the possible three types of active modes to intrinsic atomic vibrations; 2 T2g modes (one for translational motion of “Cs” and other for octahedral breathing), 1 Eg and 1 A1g mode for various stretching of Ag–Cl octahedra. Ab-initio simulation reveals dominant carrier-phonon scattering via Fröhlich mechanism near room temperature, with longitudinal optical phonons being effectively activated around 230 K. We observe a noticeable increase in hole mobility (∼4 times) with small Bi alloying, attributed to valence band (VB) maxima acquiring Bi-s orbital characteristics, thus resulting in a dispersive VB. We believe that our results should help to gain a better understanding of the intrinsic electronic and lattice dynamical properties of these compounds and provide a base toward improving the overall performance of double perovskite nanocrystals.

The perovskite‐inspired Cu2AgBiI6 (CABI) material has been gaining increasing momentum as photovoltaic (PV) absorber due to its low toxicity, intrinsic air stability, direct bandgap, and a high absorption coefficient in the range of 105 cm−1. However, the power conversion efficiency (PCE) of existing CABI‐based PVs is still seriously constrained by the presence of both intrinsic and surface defects. Herein, antimony (III) (Sb3+) is introduced into the octahedral lattice sites of the CABI structure, leading to CABI‐Sb with larger crystalline domains than CABI. The alloying of Sb3+ with bismuth (III) (Bi3+) induces changes in the local structural symmetry that dramatically increase the formation energy of intrinsic defects. Light‐intensity dependence and electron impedance spectroscopic studies show reduced trap‐assisted recombination in the CABI‐Sb PV devices. CABI‐Sb solar cells feature a nearly 40% PCE enhancement (from 1.31% to 1.82%) with respect to the CABI devices mainly due to improvement in short‐circuit current density. This work will promote future compositional design studies to enhance the intrinsic defect tolerance of next‐generation wide‐bandgap absorbers for high‐performance and stable PVs.

Perovskite-inspired Cu2AgBiI6 (CABI) absorber has recently gained increased popularity due to its low toxicity, intrinsic air stability, and wide bandgap ≈ 2 eV, which makes it ideal for indoor photovoltaics (IPVs). However, the considerable presence of both intrinsic and surface defects is responsible of the still modest indoor power conversion efficiency (PCE(i)) of CABI- based IPVs, with the short-circuit current density (JSC) being nearly half of the theoretical limit. Herein, we introduce antimony (III) (Sb3+) into the octahedral lattice sites of CABI structure, leading to CABI-Sb with substantially larger crystalline domains than CABI. The alloying of Sb3+ with bismuth (III) (Bi3+) induces changes in the local structural symmetry, in turn causing a remarkably increased formation energy of intrinsic defects. This accounts for the overall reduced defect density in CABI-Sb. CABI-Sb IPVs feature an outstanding PCE(i) of nearly 10% (9.53%) at 1000 lux, which represents an almost double PCE(i) compared to that of CABI devices (5.52%) mainly due to an improvement in JSC. This work will promote future compositional design studies to reduce the intrinsic defect tolerance of next-generation wide- bandgap absorbers for high-performance and stable IPVs.

Perovskite-inspired absorbers are promising for sustainable indoor light-harvesting. Defect mitigation and device operational stability need attention to accelerate the development of air-stable and low-toxicity photovoltaics.