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.
Hydroiodic acid (HI) additive engineering enhances the film morphology and increases the surface coverage of Cu2AgBiI6 (CABI) films. The n‐i‐p photovoltaic cells with CABI active layers with HI achieve a power conversion efficiency of 1.3% under 1 sun illumination and 4.7% under indoor white light‐emitting diode lighting, which is within the same range of commercial indoor photovoltaics.
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 triple‐cation A3Sb2X9‐based perovskite‐inspired material (PIM), with cesium, methylammonium and formamidinium occupying its A‐site, possesses a suitable band gap for indoor photovoltaics (IPVs). Reduced trap‐assisted recombination and high external quantum efficiency of triple‐cation Sb‐based PIM IPVs ensure an indoor power conversion efficiency of 6.4%, which is the highest among pnictohalide based IPVs.
Abstract
The remarkable success of lead halide perovskites (LHPs) in photovoltaics and other optoelectronics is significantly linked to their defect tolerance, although this correlation remains not ...fully clear. The tendency of LHPs to decompose into toxic lead‐containing compounds in the presence of humid air calls for the need of low‐toxicity LHP alternatives comprising of cations with stable oxidation states. To this aim, a plethora of low‐dimensional and wide‐bandgap perovskite‐inspired materials (PIMs) are proposed. Unfortunately, the optoelectronic performance of PIMs currently lags behind that of their LHP‐based counterparts, with a key limiting factor being the high concentration of defects in PIMs, whose rich and complex chemistry is still inadequately understood. This review discusses the defect chemistry of relevant PIMs belonging to the halide elpasolite, vacancy‐ordered double perovskite, pnictogen‐based metal halide, Ag‐Bi‐I, and metal chalcohalide families of materials. The defect‐driven optical and charge‐carrier transport properties of PIMs and their device performance within and beyond photovoltaics are especially discussed. Finally, a view on potential solutions for advancing the research on wide‐bandgap PIMs is provided. The key insights of this review will help to tackle the commercialization challenges of these emerging semiconductors with low toxicity and intrinsic air stability.
The perovskite-inspired Cu
AgBiI
(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 10
cm
. 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) (Sb
) is introduced into the octahedral lattice sites of the CABI structure, leading to CABI-Sb with larger crystalline domains than CABI. The alloying of Sb
with bismuth (III) (Bi
) 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.
Lead-free layered double perovskite nanocrystals (NCs), i.e., Cs
M(II)M(III)
Cl
, have recently attracted increasing attention for potential optoelectronic applications due to their low toxicity, ...direct bandgap nature, and high structural stability. However, the low photoluminescence quantum yield (PLQY, <1%) or even no observed emissions at room temperature have severely blocked the further development of this type of lead-free halide perovskites. Herein, two new layered perovskites, Cs
CoIn
Cl
(CCoI) and Cs
ZnIn
Cl
(CZnI), are successfully synthesized at the nanoscale based on previously reported Cs
CuIn
Cl
(CCuI) NCs, by tuning the M(II) site with different transition metal ions for lattice tailoring. Benefiting from the formation of more self-trapped excitons (STEs) in the distorted lattices, CCoI and CZnI NCs exhibit significantly strengthened STE emissions toward white light compared to the case of almost non-emissive CCuI NCs, by achieving PLQYs of 4.3% and 11.4% respectively. The theoretical and experimental results hint that CCoI and CZnI NCs possess much lower lattice deformation energies than that of reference CCuI NCs, which are favorable for the recombination of as-formed STEs in a radiative way. This work proposes an effective strategy of lattice engineering to boost the photoluminescent properties of lead-free layered double perovskites for their future warm white light-emitting applications.
Ag 3 BiI 6 (ABI) is one of the most widely explored lead‐free perovskite‐inspired materials for eco‐friendly solar cell applications. However, despite the intense research efforts, the photovoltaic ...performance of ABI‐based devices remains very modest, primarily due to poor film morphology and ineffective charge extraction. This work aims at investigating the potential benefits of a thermally evaporated cesium iodide (CsI) interlayer on the performance of ABI‐based solar cells. Upon the addition of CsI atop the ABI layer in the device stack, the solar cells deliver a power conversion efficiency (PCE) of 2.27%. This is the highest efficiency reported for ABI solar cells employing a similar device architecture. It is found that the enhancement in PCE is largely due to improvement in the ABI|hole transport layer interface upon the introduction of CsI interlayer. The improvement is largely ascribed to enhanced surface coverage upon introduction of CsI interlayer, as evidenced by our comprehensive microscopy studies. Furthermore, impedance spectroscopy analysis is employed to provide further insights into the changes in charge transfer dynamics interlayer that dictate the enhancement of fill factor and short‐circuit current density in the devices. The findings indicate that the addition of CsI promotes charge transfer and minimizes recombination losses.
Indoor Photovoltaics
In article number 2203768, Paola Vivo and co‐workers propose the use of low‐toxicity copper‐silver‐bismuth iodide (Cu2AgBiI6) light‐harvester for indoor photovoltaics (IPVs). ...When treating Cu2AgBiI6 with hydroiodic acid, the film morphology is enhanced, leading to IPVs with a power conversion efficiency up to 4.7%.
Lead halide perovskite (LHP) photovoltaics deliver high voltages even under low-light illumination intensities, thus emerging as a promising indoor photovoltaic (IPV) technology. The doping of the ...2,2′,7,7′-tetrakis(N,N-di-p-methoxyphenylamino)-9,9′-spirobifluorene (Spiro-OMeTAD) hole-transport layer (HTL) is the most widely adopted strategy for high-performance LHP-based solar cells. Yet, the importance of Spiro-OMeTAD doping is unclear in the context of indoor photovoltaics. In this report, we examine the role of the traditional Spiro-OMeTAD dopants on the performance of LHP-based IPVs. The diminished influence of the series resistance under indoor lighting leads to an improved fill factor of IPV devices even in the absence of the dopants. The pristine (dopant-free) Spiro-OMeTAD HTL ensures a power conversion efficiency (PCE) as high as 25.6% at 1,000 lux, comparable to that of 29.7% in the presence of the dopants, and an open-circuit voltage of ≈0.65 V even at 50 lux. The undoped Spiro-OMeTAD-containing devices exhibit a ≈25% gain in their PCE under long-term and continuous white light illumination at the maximum power point, thus leading to the PCE values on par or higher than those of employing doped Spiro-OMeTAD. Furthermore, the current–voltage hysteresis behavior of the undoped Spiro-OMeTAD-containing devices remains unchanged in the 100 to 1,000 lux light-intensity range, unlike the case of doped Spiro-OMeTAD HTL. Our findings suggest that the dopants in Spiro-OMeTAD HTL are not required to achieve efficient, stable, and reliable IPV performance, and the optimization of the various device constituents for outdoor solar cell applications may not necessarily lead to the best performance for indoor photovoltaics.
This study aims to enhance the performance of perovskite solar cells (PSCs) by optimizing the interface between the perovskite and electron transport layers (ETLs). Additionally, we plan to protect ...the absorber layer from ultraviolet (UV) degradation using a ternary oxide system comprising SnO2, strontium stannate (SrSnO3), and strontium oxide (SrO). In this structure, the SnO2 layer functions as an electron transport layer, SrSnO3 acts as a layer for UV filtration, and SrO is employed to passivate the interface. SrSnO3 is characterized by its chemical stability, electrical conductivity, extensive wide band gap energy, and efficient absorption of UV radiation, all of which significantly enhance the photostability of PSCs against UV radiation. Furthermore, incorporating SrSnO3 into the ETL improves its electronic properties, potentially raising the energy level and improving alignment, thereby enhancing the electron transfer from the perovskite layer to the external circuit. Integrating SrO at the interface between the ETL and perovskite layer reduces interface defects, thereby reducing charge recombination and improving electron transfer. This improvement results in higher solar cell efficiency, reduced hysteresis, and extended device longevity. The benefits of this method are evident in the observed improvements: a noticeable increase in open-circuit voltage (V oc) from 1.12 to 1.16 V, an enhancement in the fill factor from 79.4 to 82.66%, a rise in the short-circuit current density (J sc) from 24.5 to 24.9 mA/cm2 and notably, a marked improvement in the power conversion efficiency (PCE) of PSCs, from 21.79 to 24.06%. Notably, the treated PSCs showed only a slight decline in PCE, reducing from 24.15 to 22.50% over nearly 2000 h. In contrast, untreated SnO2 perovskite devices experienced a greater decline, with efficiency decreasing from 21.79 to 17.83% in just 580 h.
