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Schematic of solar cell structure (a) and the corresponding approximate energy level schematic picture of the device (b).
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In this work, silver-bismuth-halide thin films, exhibiting low toxicity and good stability, were explored systemically by gradually substituting iodide, I, with bromide, Br, in AgBi2I7 system. It was found that the optical bandgap can be tuned by varying the I/Br ratio. Moreover, the film quality was improved when introducing a small amount of Br....
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GaAs is often used as a multijunction subcell due to its high material quality on GaAs substrates, despite having a non-optimal bandgap. The bandgap can be beneficially reduced using many layers of thin, strain-balanced GaInAs in a superlattice or quantum well device, but achieving excellent carrier collection without increased recombination has pr...
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... Both valence-and conduction-band edges are expected to be affected by Br substitution, but the changes might be considerably small. [29] The steady-state PL spectra presented in Figure 2(b) show that the thin film with 5 % Br displays the highest PL intensity. The peak positions do not shift with Br substitution. ...
... Br might have slowed down the reaction, resulting in increased grain size. [29] From the cross-sectional SEM image shown in To evaluate the influence of Br substitution on photovoltaic performance, we fabricated solar cells with the following structure: F-doped SnO 2 (FTO) coated glass / compact TiO 2 (c-TiO 2 ) / m-TiO 2 + AgBi(I 1 À x Br x ) 4 / Poly[bis(4-phenyl)(2,4,6trimethylphenyl)amine] (PTAA) / Ag, as shown in Figure 4(a). Notably, the PTAA solutions did not contain any additives because we were concerned about their potential for corroding AgBi(I 1 À x Br x ) 4 . ...
Despite the rapid development of Pb‐based perovskites, the presence of toxic Pb and insufficient stability remain discouraging factors for the commercialization of perovskite solar cells. Therefore, research on Pb‐free absorbers exhibiting long‐term stability is required. Herein, AgBi(I1−xBrx)4 thin films having a hexagonal rudorffite structure were fabricated using a solution process in ambient atmosphere for cost‐effective and environmentally benign photovoltaics. Br substitution increases the grain size and results in a pinhole‐free morphology. Furthermore, photoluminescence analyses confirm that Br substitution reduces the trap‐state density. Consequently, device efficiency is enhanced through Br substitution. Importantly, Br substitution results in considerably improved device stability, with devices maintaining 80 % of their initial efficiency for 26 days in ambient atmosphere without encapsulation.
... Besides, a shift towards a shorter wavelength was observed, indicating the possibility of band-gap tuning. The power conversion efficiency for bromine incorporated solar cell device(10% Br) was found to be almost twice (1.02%) compared to that of pure iodide [156]. ...
Organic-inorganic lead halide perovskite solar cells have paved the way toward producing low-cost thin-film solar cells. The tremendous improvement in power conversion efficiency greater than 25%, suitable optoelectronic properties and easiness of the fabrication method have triggered the aspiration to think thoroughly about the commercialisation stage. However, lead toxicity and poor stability stand as the main obstruction. Therefore, the great way toward commercialisation is by considering all inorganic lead-free halide perovskites solar cells (AILFHP). Since the first AILFHP solar cell was fabricated, several challenges have been conquered by modifying the fabrication techniques and device architecture. This review entails the modification done to fabrication methods, particularly the application of solvent and composition engineering techniques. Several deposition techniques with and without excess reactants and precursor–solvent interaction have been thoroughly discussed. It further discusses the effect of mixed cations and mixed anions, potential application areas, obstacles, and future commercialisation prospects.
... However, AgBiBr 4 [SG:52] and AgBiBr 4 [SG:62] have the potential for use as red-light emitter materials owing to their direct bandgaps, as depicted in figures 9(a) and (b). Despite the relatively large convex hull (0.033 eV/atom), the phase stability of AgBiBr 4 can be improved by applying compositional engineering to the A-and X-sites[92][93][94][95][96]. ...
Toxicity is the main bottleneck for the commercialization of Pb halide perovskites. Bi has been considered a promising metal cation to replace Pb because of its comparable electronic structures with Pb and better stability. Although experimental and theoretical studies have proposed various Bi-based halides, the present achievements in photovoltaic cells and other photoelectronic device fields do not compete with Pb analogs. Thermodynamic stability, bandgap control, and enhancement of carrier transport are fundamental challenges in the context of intrinsic material properties for developing highly efficient Bi-based devices. This study evaluates the potential of Bi-based halide compounds with good stability and electronic properties through high-throughput density functional theory calculations. Lattice structures and compositions are selected based on previous reports and an open material database. Then, we expanded our dataset to cover all possible compositional variations of A- and X-sites and alloying to B-sites. We examined over six-hundred candidates and found ten new candidates that have not been reported previously. Rb 3 SbBiI 9 exhibits the best-expected efficiency for high-efficiency solar cells among selected compounds, and other compounds can be used as visible-light-generation sources. Analysis of the screening procedure revealed that vacancy-ordered (A 3 B 2 X 9 )-type Bi-halides exhibit significantly favorable characteristics when compared with those of double perovskites and rudorffite-like structures for Bi-based photoelectronic devices.
... Figure 23 depicts the energy band levels of each composition compared to MA 3 Bi 2 I 9 . Sansom et al reported absorption coefficients for AgBiI 4 to be in the range of 10 5 -10 6 cm −1 comparable to lead perovskites and the VB mainly consist of I 5p and Ag 4d while CB consists of Bi 6p and I 5p orbitals, which was similarly presented for AgBi 2 I 7 [331,336]. A broad PL emission at 720 nm was observed in Ag 3 BiI 6 thin films with lifetimes between 1 to 200 ns [332,333]. ...
... It was shown that Br 4p states contribute to the VB and CB edges and thus influence the band gap energy, while not changing the crystal structure for amounts lower than 20%. Higher amounts lead to AgI and BiBr 3 impurities because of the instability of the pure bromide based compound [336]. In order to reduce the band gap and raise the VB level, Pai et al used sulfur doping into the rudorffite materials to obtain A a B b I a+3b−2x S x employing bismuth tris(4methylbenzodithitoate) along with BiI 3 and AgI precursors. ...
... Several other preparation techniques were introduced to fabricate rudorffite based solar cells such as microwave-assisted annealing [328], dual-source evaporation [348] and dynamic spin-coating with ramped annealing [337]. Additionally, PTAA was found to be more suitable compared to P3HT in AgBiI 4 solar cells due to lower HOMO level (−5.14 eV for PTAA vs. and compared to all reported methods such as compositional tuning with Br − [336,352] and Cu- [344], alloying with Sb- [343] and Cs- [353], doping with reduced graphene oxide and multi-walled carbon nanotubes [115], sulfur-doping was demonstrated as a most successful strategy to narrow the band gap and upshift the VB levels, which lead to the highest PCE of 5.44% reported so far for Ag 3 BiI 5.92 S 0.04 rudorffite based solar cells. The best performing Ag 3 BiI 5.92 S 0.04 solar cells were fabricated from solution using an HI additive and gasquenching method, and maintained 90% of the initial PCE after 45 days under ambient conditions [342]. ...
The efficiency of organic-inorganic hybrid lead halide perovskite solar cells (PSCs) has increased over 25% within a frame of ten years, which is phenomenal and indicative of the promising potential of perovskite materials in impacting the next generation solar cells. Despite high technology readiness of PSCs, the presence of lead has raised concerns about the adverse effect of lead on human health and the environment that may slow down or inhibit the commercialization of PSCs. Thus, there is a dire need to identify materials with lower toxicity profile and comparable optoelectronic properties in regard to lead-halide perovskites. In comparison to tin-, germanium-, and copper-based PSCs, which suffer from stability issues under ambient operation, bismuth-based perovskite and perovskite-inspired materials have gained attention because of their enhanced stability in ambient atmospheric conditions. In this topical review, we initially discuss the background of lead and various lead-free perovskite materials and further discuss the fundamental aspects of various bismuth-based perovskite and perovskite-inspired materials having a chemical formula of A 3 Bi 2 X 9 , A 2 B′BiX 6 , B′ a Bi b X a+3b (A = Cs ⁺ , MA ⁺ and bulky organic ligands; B′ = Ag ⁺ , Cu ⁺ ; X = I ⁻ , Cl ⁻ , Br ⁻ ) and bismuth triiodide (BiI 3 ) semiconducting material particularly focusing on their structure, optoelectronic properties and the influence of compositional variation on the photovoltaic device performance and stability
... Finally, semiconductors made of non-toxic or low-toxicity elements are most attractive, as they could easily be used in the many environments required by emerging application domains. Among perovskite-inspired solution-processed semiconductors, rudorffites have attracted increasing attention over the last few years particularly because of their three-dimensional structure and because they do not contain heavily toxic elements [14][15][16][17][18][19][20][21][22][23][24]. Their structure relies on metal-halide [MX 6 ] octahedra (where M is a monovalent or trivalent metal, e.g., Bi, Sb, Cu, Ag, and X is a halide) as the building blocks of a three-dimensional lattice featuring an edgesharing packing motif [17][18][19]. ...
... Their structure relies on metal-halide [MX 6 ] octahedra (where M is a monovalent or trivalent metal, e.g., Bi, Sb, Cu, Ag, and X is a halide) as the building blocks of a three-dimensional lattice featuring an edgesharing packing motif [17][18][19]. In particular, silver-bismuth iodides (Ag a Bi b I x , x = a + 3b) have been identified as particularly promising, as evidenced by their increasing attention in photovoltaic research [14,15,[17][18][19][20][21][22][23][24]. In fact, their potential is confirmed by a rapid rise in solar power conversion efficiency (up to 4.3%) [14,15,[19][20][21][22][23]. ...
... In particular, silver-bismuth iodides (Ag a Bi b I x , x = a + 3b) have been identified as particularly promising, as evidenced by their increasing attention in photovoltaic research [14,15,[17][18][19][20][21][22][23][24]. In fact, their potential is confirmed by a rapid rise in solar power conversion efficiency (up to 4.3%) [14,15,[19][20][21][22][23]. Despite their promising optoelectronic properties, the capabilities of silver-bismuth iodides for photodetection have not been explored to date. ...
Recent years have witnessed intense research efforts in the development of solution-processible semiconductors with perovskite/perovskite-inspired structures for optoelectronics. Among them, silver-bismuth-halides have been identified as particularly promising, as they possess well-conditioned bulk properties and do not comprise heavily toxic elements. While attracting significant attention in photovoltaics, their potential for photodetection has not been explored to date. In view of their strong absorption through the visible, this study investigates their applicability to near-infrared (NIR)-blind visible light photodetection, as particularly significant to emerging application domains, e.g., wearable optoelectronics and the Internet of Things. With a focus on Ag2BiI5, this study realizes self-powered photodetectors with a near-constant ≈ 100 mA W-1 responsivity through the visible, a NIR rejection ratio > 250, a long-wavelength responsivity onset matching standard colorimetric functions, and a linear photoresponse over > 5 orders of magnitude. The optoelectronic characterization presented here additionally provides insight into the workings of Ag2BiI5, allowing the identification of the role played by the carrier collection distance in self-powered operation, and the rationalization of its optoelectronic behavior in terms of one-center models. Therefore, this study provides positive indications on the outlook of Ag2BiI5 toward emerging applications requiring low-cost and low-power NIR-blind visible light photodetectors.
Silver‐bismuth‐based perovskite‐inspired materials (PIMs) are increasingly being explored as non‐toxic materials in photovoltaic applications. However, many of these materials exhibit an ultrafast localization of photogenerated charge carriers that is detrimental for charge‐carrier extraction. In this work, such localization processes are explored for thermally evaporated thin films of compositions lying along the (AgI)x(BiI3)y series, namely BiI3, AgBi2I7, AgBiI4, Ag2BiI5, Ag3BiI6, and AgI, to investigate the impact of changing Ag⁺/Bi³⁺ content. A persistent presence of ultrafast charge‐carrier localization in all mixed compositions and BiI3, together with unusually broad photoluminescence spectra, reveal that eliminating silver will not suppress the emergence of a localized state. A weak change in electronic bandgap and charge‐carrier mobility reveals the resilience of the electronic band structure upon modifications in the Ag⁺/Bi³⁺ composition of the mixed‐metal rudorffites. Instead, chemical composition impacts the charge‐carrier dynamics indirectly via structural alterations: Ag‐deficient compositions demonstrate stronger charge‐carrier localization most likely because a higher density of vacant sites in the cationic sublattice imparts enhanced lattice softness. Unraveling such delicate interplay between chemical composition, crystal structure, and charge‐carrier dynamics in (AgI)x(BiI3)y rudorffites provides crucial insights for developing a material‐by‐design approach in the quest for highly efficient Bi‐based PIMs.
Cu2AgBiI6 (CABI) is a promising perovskite-inspired absorber for solar cells due to its direct band gap and high absorption coefficient. However, the nonradiative recombination caused by the high extrinsic trap density limits the performance of CABI-based solar cells. In this work, we employ halide engineering by doping bromide anions (Br–) in CABI thin films, in turn significantly improving the power conversion efficiency (PCE). By introducing Br– in the synthetic route of CABI thin films, we identify the optimum composition as CABI-10Br (with 10% Br at the halide site). The tailored composition appears to reduce the deep trap density as shown by time-resolved photoluminescence and transient absorption spectroscopy characterizations. This leads to a dramatic increase in the lifetime of charge carriers, which therefore improves both the external quantum efficiency and the integrated short-circuit current. The photovoltaic performance shows a significant boost since the PCE under standard 1 sun illumination increases from 1.32 to 1.69% (∼30% relative enhancement). Systematic theoretical and experimental characterizations were employed to investigate the effect of Br– incorporation on the optoelectronic properties of CABI. Our results highlight the importance of mitigating trap states in lead-free perovskite-inspired materials and that Br– incorporation at the halide site is an effective strategy for improving the device performance.
Indoor photovoltaics (IPVs) have garnered significant attention in recent years due to their potential to empower small portable electronic devices and the Internet of Things (IoT). After silicon solar cells, it is now widely acknowledged that the dominant technology in the field of outdoor/indoor photovoltaics is hybrid lead (Pb) halide perovskites. Despite the fascinating characteristics of hybrid Pb‐halide perovskites, the presence of toxic Pb is regarded as one of the major factors that prevent commercialization. Low‐toxic, Pb‐free, and stable perovskites are also being used in outdoor solar cells (ODSCs), but their efficiencies are low due to large bandgap (i.e. ∽2.0 eV). Recently, some of the stable, Pb‐free perovskite materials have drawn great interest due to their initial performance across various fields, including light‐emitting diodes (LEDs), photodetectors, X‐rays, photocatalysis, ODSCs, and in IPVs. In this perspective, we summarized the current status and prospects for Pb‐free halide perovskites, chalcogen perovskites, silver bismuth halide (A a B b X a+3b ) family, and other chalcogen materials are being explored to speed up the progress of IPVs.
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Leveraging the dimensionality-modulation method to further boost the device efficiency and stability is the future roadmap for the development of lead-free perovskite solar cells.
Quaternary copper‐silver‐bismuth‐iodide compounds represent a promising new class of wide‐bandgap (2 eV) semiconductors for photovoltaic and photodetector applications. In this study, vapor phase co‐evaporation is utilized to fabricate Cu2AgBiI6 thin films and photovoltaic devices. The findings show that the properties of vapor‐deposited films are highly dependent upon processing temperature, exhibiting increased pinhole density and transforming into a mixture of quaternary, binary, and metallic phases depending on the post‐deposition annealing temperature. This change in phase is accompanied by an enhancement in photoluminescence (PL) intensity and charge‐carrier lifetime, along with the emergence of an additional absorption peak at high energy (≈3 eV). Generally, increased PL is a desirable property for a solar absorber material, but this change in PL is ascribed to the formation of CuI impurity domains, whose defect‐mediated optical transition dominates the emission properties of the thin film. Via optical pump terahertz probe spectroscopy, it is revealed that CuI impurities hinder charge‐carrier transport in Cu2AgBiI6 thin films. It is also revealed that the predominant performance limitation in Cu2AgBiI6 materials is the short electron‐diffusion length. Overall, the findings pave the way for potential solutions to critical issues in copper‐silver‐bismuth‐iodide materials and indicate strategies to develop environmentally compatible wide‐bandgap semiconductors.
