Lead‐free perovskite‐inspired materials (PIMs) are gaining attention in optoelectronics due to their low toxicity and inherent air stability. Their wide bandgaps (≈2 eV) make them ideal for indoor light harvesting. However, the investigation of PIMs for indoor photovoltaics (IPVs) is still in its infancy. Herein, the IPV potential of a quaternary PIM, Cu2AgBiI6 (CABI), is demonstrated upon controlling the film crystallization dynamics via additive engineering. The addition of 1.5 vol% hydroiodic acid (HI) leads to films with improved surface coverage and large crystalline domains. The morphologically‐enhanced CABI+HI absorber leads to photovoltaic cells with a power conversion efficiency of 1.3% under 1 sun illumination—the highest efficiency ever reported for CABI cells and of 4.7% under indoor white light‐emitting diode lighting—that is, within the same range of commercial IPVs. This work highlights the great potential of CABI for IPVs and paves the way for future performance improvements through effective passivation strategies.

Antimony‐based perovskite‐inspired materials (PIMs) are solution‐processable halide absorbers with interesting optoelectronic properties, low toxicity, and good intrinsic stability. Their bandgaps around 2 eV make them particularly suited for indoor photovoltaics (IPVs). Yet, so far only the fully inorganic Cs3Sb2ClxI9−x composition has been employed as a light‐harvesting layer in IPVs. Herein, the first triple‐cation Sb‐based PIM (CsMAFA‐Sb) in which the A‐site of the A3Sb2X9 structure consists of inorganic cesium alloyed with organic methylammonium (MA) and formamidinium (FA) cations is introduced. Simultaneously, the X‐site is tuned to guarantee a 2D structure while keeping the bandgap nearly unchanged. The presence of three A‐site cations is essential to reduce the trap‐assisted recombination pathways and achieve high performance in both outdoor and indoor photovoltaics. The external quantum efficiency peak of 77% and the indoor power conversion efficiency of 6.4% are the highest values ever reported for pnictohalide‐based photovoltaics. Upon doping of the P3HT hole‐transport layer with F4‐TCNQ, the power conversion efficiency of CsMAFA‐Sb devices is fully retained compared to the initial value after nearly 150 days of storage in dry air. This work provides an effective compositional strategy to inspire new perspectives in the PIM design for IPVs with competitive performance and air stability.

The considerable potential of perovskite-inspired Cu2AgBiI6 (CABI) photovoltaics under both solar and artificial lighting has been recently highlighted. However, to realistically ensure the suitability of CABI-based indoor photovoltaics (IPVs) to...

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.