processes during vapor phase deposition along with the develop- ment of in situ and in-line monitoring techniques for efficient process control are crucial. Next to addressing the aforementioned key cha

The gap

Consensus across the literature

Supporting evidence — 8 representative gaps

• Strategic development of stable and efficient lead-free perovskite solar cells (2026) · doi

  The toxicity of lead-based perovskite solar cells has driven intense research into economical, clean, and sustainable lead-free alternatives to PV tech- nology. Although there are many promising options for LFPSCs, Tin (Sn), bismuth (Bi), Antimony (Sb), and germanium (Ge) are primarily used for this purpose due to their non-toxicity, intrinsic properties, and eco- friendliness. However, many obstacles, such as stability and low efficiency, are holding back their practical application. Our review primarily focuses on strategies to enhance the stability and efficiency of lead-free perovskite solar cells. This paper discusses the limitations of Pb-based perovskites and explores promising lead-free alternatives. It further describes the major issues with lead-free perovskite solar cells and delves into strategies to improve their stability and performance. It also provides an overview of recent developments in lead-free perovskite solar cells. Since the first report on lead-free CsSnI3-based PSC devices, the field has seen rapid growth, and the efficiency of lead-free perovskite solar cells has increased from below 1% to 15%. In this context, lead-free perovskites present a compelling direction due to their intrinsically stable phases and compatibility with existing fab- rication technologies. Despite recent advances in synthetic techniques and device engineer- ing, lead-free perovskites still face challenges, including stability and effi- ciency issues, high cost, complex fabrication processes, and poor physicochemical properties. Figure 6 provides a graphical summary of lead- free alternatives and key strategies to improve the efficiency and stability of LFPSCs. Compositional engineering by varying the cation and anion is an effective approach to stabilizing the perovskite structure. In particular, the mixed-cation or mixed-anion strategy yields a high-quality thin film with phase control and defect suppression. Moreover, the performance of lead- free perovskite solar cells is significantly limited by rapid crystallization and poor film quality. The crystallization process can be controlled by solvent interactions, formation of intermediate adducts, and anion substitution. Selective solvents and organic moieties such as DMSO, chlorobenzene, or carboxylic groups retard crystallization and yield compact, pinhole-free thin films. Film quality can be improved through one- or two-step coating techniques and vapor deposition methods. Many atypical synthesis approaches, such as vapor-assisted solution process (VASP) or high-low vacuum deposition (HLVD), are introduced to facilitate the preparation of high-quality thin films. Sn and Ge-based perovskite solar cells are unstable under environmental conditions because they immediately convert from Sn2+ and Ge2+ states into Sn4+ and Ge4+. The use of additives such as SnF2 can suppress oxidation and increase stability. Bidentate ligands or Lewis bases, such as thiourea, can also chelate Sn and inhibit its conversion, the

  Keywords: lead free perovskite solar cells stability ciency based high quality alternatives strategies perovskites anion thin
• All-perovskite tandem solar cells: from fundamentals to technological progress (2024) · doi

  Many state-of-the-art PV technologies have gradually pro- gressed from single-junction solar cells to double or triple- junction solar cells. The increasing attention on the APTSCs has been proven by the number of published papers annually and the improved device performances. In this review, we introduced the fundamentals of APTSCs, the approaches for the current issues, and the potential of APTSCs in the future. The tandem technology is one of the key methods beyond the single junction S–Q limit. The tunable bandgap of the perovskite provides the privilege of high efficiency towards ideally 45% instead of 33%. Additionally, the low cost originat- lightweight, scale-up ing from the thin film technology, chances, and eco-friendly technology related to a low CO2 footprint are highly attractive. We elaborated on various types of APTSCs considering 2T and 4T architectures and classified APTSCs into bifacial, This journal is © The Royal Society of Chemistry 2024Energy Environ. Sci., 2024, 17, 4390–4425 | 4417Open Access Article. Published on 10 May 2024. Downloaded on 6/14/2026 7:15:07 AM. This article is licensed under a Creative Commons Attribution 3.0 Unported Licence.View Article OnlineEnergy & Environmental Science

  Keywords: aptscs junction technology article single solar cells published energy state technologies gradually gressed double triple
• Vapor phase deposition of perovskite photovoltaics: short track to commercialization? (2024) · doi

  Vapor phase deposition of perovskite photovoltaics: short track to commercialization?† *a David T. Moore, Tobias Abzieher, Jared Silvia,c Hairen Tan, Maximilian T. Hoerantner,g Beom-Soo Kim, Jan Christoph Goldschmidt, Juliane Borchert,op Michael D. McGehee, Jay B. Patel, s Annalisa Bruno *a Marcel Roß, d Quentin Jeangros,e Christophe Ballif,ef b Steve Albrecht, b i Paul Pistor, h Henk J. Bolink, l Yu-Hsien Chiang,mn Samuel D. Stranks, mn jk t and Ulrich W. Paetzold *u q Monica Morales-Masis, r While perovskite-based photovoltaics (PV) is progressing toward commercialization, it remains an open question which fabrication technology – solution-based, vapor-based, or combinations – will pave the way to faster economic breakthrough. The vast majority of research studies make use of solution- processed perovskite thin films, which benefit from a rapid optimization feedback and inexpensive to procure tools in modern research laboratories, but vapor phase deposition processes dominate today’s established thin-film manufacturing. As research and development of vapor phase processed perovskite thin films are still strongly underrepresented in literature, their full potential is yet to be identified. In this collaborative perspective of academic influenced by industrial views, we convey a balanced viewpoint on the prospects of vapor-based processing of perovskite PV at an industrial scale. Our perspective highlights the conceptual advantages of vapor phase deposition, discusses the most crucial process parameters in a technology assessment, contains an overview about relevant global industry clusters, and provides an outlook on the commercialization perspectives of the perovskite technology Received 27th September 2023, Accepted 2nd January 2024 DOI: 10.1039/d3ee03273f rsc.li/ees in general. a National Renewable Energy Laboratory (NREL), Golden, CO, USA. E-mail: [email protected], [email protected] b Helmholtz Zentrum Berlin (HZB), Berlin, Germany c BlueDot Photonics Inc, Seattle, WA, USA d Nanjing University, Nanjing, China e Centre Suisse d’Electronique et de Microtechnique (CSEM), Neuchaˆtel, Switzerland f E´cole Polytechnique Fe´de´rale de Lausanne (EPFL), Institute of Electrical and Micro Engineering (IEM), Photovoltaics and Thin-Film Electronics Laboratory, Neuchaˆtel,

  Keywords: vapor perovskite phase based thin deposition photovoltaics commercialization technology david moore tobias abzieher solution processed
• Vapor phase deposition of perovskite photovoltaics: short track to commercialization? (2024) · doi

  Fig. B1 General concept of vapor processing of perovskite solar cells. (a) Concept for the in-line fabrication of fully vapor-processed perovskite solar cells together with the general processes taking place during the co-evaporation of organic and inorganic compounds (see enlarged detail). (b) Sample layer stack sequence for opaque perovskite solar cells. processing and the present TEA for vapor processing. Specifi- cally, the following discussion is based on very conservative assumptions with regard to key factors such as production yield (90% for both, solution and vapor processing), material usage (same for both techniques), and post-treatment or annealing (disregarded but critical for solution processing) that are more likely to be favorable for solution processing in these calcula- tions, thus, more likely to result in a rather conservative outcome for the case of vapor processing. A detailed discussion about these assumptions is found in the ESI.† In terms of overall costs, the principal differences between vapor and solution processing are the production costs, mostly affected by throughput (accurately expressed in industrial deposition equipment by the dynamic deposition rate in nm m min(cid:2)1, which is the thickness of the deposited film multiplied by the substrate speed) and yield, and the CAPEX associated with the vacuum equipment. Under the assumption that all other layers in the device stack are the same for both absorber deposition routes, these differences only impact the deposition of the absorber layer. Both at the research and industrial scales, high production yields are easier to achieve via vapor-based deposition methods, resulting in a decisive cost advantage of these methods over solution processing. On the other hand, production throughput, which impacts both the total production costs and the CAPEX, is typically lower for vapor processing given the generally lower deposition rates of common vapor processing methods. However, production throughput in vapor processing can be readily manipulated by placing multiple deposition sources in series, by applying deposition sources with larger evaporation zones, or by increas- ing the deposition rate for each individual source (as long as the employed materials feature sufficiently high temperature resistances). In fact, there have been demonstrations, at the laboratory scale, of deposition rates above 100 nm min(cid:2)1 by sputtering, flash sublimation, and vapor transport techniques, all methods that operate between 1 (cid:3) 10(cid:2)4 and 1 (cid:3) 10(cid:2)5 Torr.43–45 Therefore, the herein employed CAPEX model refrains from considering ultra-high-vacuum equipment and only considers the use of less expensive high-vacuum equip- ment. Given these preliminary notes, deposition rates and the number of sources are obviously the most important para- meters that need to be optimized in order to bring production costs and CAPEX to a competitive level. It is highlighted that combinati

  Keywords: processing vapor deposition production solution costs capex high perovskite solar cells throughput equipment vacuum rates
• Vapor phase deposition of perovskite photovoltaics: short track to commercialization? (2024) · doi

  Fig. 2 State-of-the-art achievements for vapor processed perovskite-based solar cells. Exemplary comparison of champion solar cells employing single- and double-cation hybrid perovskite absorbers prepared by either solution- (left) or vapor-based (right) approaches with respect to the theoretical detailed balance of the individual solar cell parameters. It is noted here that the figure does not provide a benchmark, but only revisits the state-of-the-art metrics of three prominent examples. MAPbI3 is highlighted here as it is still the most studied vapor processed perovskite material. CsFAPbI3 and CsFAPb(IxBr1(cid:2)x)3 are examples for highly efficient vapor processed standard- and wide-bandgap materials. often-claimed preeminence in thin-film quality of solution- based approaches is most likely not founded on fundamental scientific limitations of vapor-based approaches, but rather just a result of the personnel and monetary disparity in research and development in the field, which resulted in a significant backlog for vapor processing over the years. In fact, one could likewise expect equal or even better thin-film qualities for vapor-processed perovskite materials given their simpler nucleation and thin-film formation processes as well as the absence of residual solvents and pinholes in the final thin film. It should be noted here that the vapor-processed CsFAPbI3 absorber employs PbCl2 as a crystallization agent while the solution-based reference does not. As PbCl2 in vapor processing acts similarly on the crystallization dynamics as the for example the exact choice of solvent systems or anti-solvent treatments in solution processing, the comparison chosen here is believed to be still reasonable. When comparing champion solar cells prepared with solution- or vapor-based perovskite absorbers (see Fig. 2 and Fig. S2 as well as Table S2 in the ESI†), the latter in many cases outperform their solution-based counterparts in terms of fill factor, given the improved uniformity and conformality of vapor-based deposition – characteristics that are of particular importance for the prevention of losses via shunt and series resistances at larger scales. However, lower open-circuit vol- tages and lower short-circuit current densities is often observed for vapor-based absorbers devices (see Tables S3 and S4 in the ESI†). Deficits in open-circuit voltage in vapor-processed per- ovskite solar cells are attributed to a generally lower opto- electronic absorber quality accompanied by the presence of non-passivated defect states inside the absorber as well as at its interfaces with adjacent charge transport layers, resulting in non-radiative recombination and in turn a limited maximum extractable open-circuit voltage of the solar cell.48–50 In fact, both photoluminescence quantum yield (PLQY) and charge carrier lifetimes of vapor-processed perovskite absorbers – especially for co-evaporated hybrid perovskite materials – have been shown to be up to one order of

  Keywords: vapor based processed perovskite solar solution cells absorbers here thin film circuit approaches materials processing
• Vapor phase deposition of perovskite photovoltaics: short track to commercialization? (2024) · doi

  vapor-based approaches in the range of just one minute) to be able to compete with solution processing approaches as well as other thin-film PV technologies. Such high deposition rates in vapor processes have been demonstrated for other thin-film materials to be achievable in an industrial setting. For example, First Solar, Inc. successfully deposits its cadmium telluride absorbers at rates of 10 000 nm min(cid:2)1 and above using a technique called vapor transport deposition.76,77 Despite these encouraging achieve- ments, for perovskite materials reported so far are rather slow-throughput approaches whose deposition rates typically do not exceed values of 10 nm min(cid:2)1 – particularly for approaches that result in the highest perfor- mance (see Fig. 3). The overall deposition rate of a vapor process is affected by two parameters: (1) geometrical consid- erations of the deposition system and its evaporation sources and (2) fundamental temperature limitations of the employed precursor materials. Deposition rates can be significantly enhanced by increasing the number of consecutive deposition sources, increasing the evaporation area of the source, or by lowering the throw distance between sources and substrate. Up to date, academic research on vapor processing is focused on systems employing point-like evaporation sources, whose appli- cation in an industrial setting is considered to be of less relevance. For the further advancement of the throughput in vapor-processed perovskite absorbers, the development of alter- native (e.g., linear or arial) source geometries and investigation of their suitability for the fabrication of uniform and reprodu- cible perovskite thin films is considered crucial. In that regard, also the continuous operation of these sources (e.g., by adding appropriate powder feeding systems) needs to be investigated, as downtime for material replacement is considered a major bottleneck on the way toward high-throughput vapor proces- sing of perovskite materials – particularly compared to fast solution-based printing techniques. While for the development of industrially capable evapora- tion equipment major learnings can be directly translated from existing thin-film technologies, input from academia is vital for the development of intrinsically faster deposition processes. Most importantly, a thorough understanding of the limitations of established vapor processes and how they can be overcome is required. In that regard, a better understanding of the challen- ging evaporation characteristics of the organic halides is of particular importance. To date, high performance perovskite solar cells prepared by vapor-based approaches rely on the use of organic halides (i.e., methylammonium and formamidinium halides), which have been reported to show at least partial decomposition at elevated temperatures and in turn are limited to lower evaporation source temperatures (typically o200 1C), thus, slow deposition rates.59,60,78,79 The ex

  Keywords: vapor deposition approaches rates perovskite evaporation sources thin materials based film high processes throughput source
• Vapor phase deposition of perovskite photovoltaics: short track to commercialization? (2024) · doi

  Fig. 5 Deposition focuses of industrial manufacturing of perovskite PV and related business sectors. (a) Number of companies employing certain deposition techniques by business sector and region. (b) Worldwide share of different deposition techniques for module and equipment manufacturing for established and early-stage companies. This information has been collected by an industry survey or via publicly available information as outlined in the ESI.† TECHNOLOGIES AG, or the VON ARDENNE GmbH commercia- lize large-area and high throughput process equipment for perovskite deposition.93,118,119 Moreover, other European com- panies like FOM Technologies (Denmark) as well as EVOLAR AB (Sweden), the latter of which was recently acquired by First Solar Inc. (United States), have positioned themselves in the field.92,120 With respect to materials suppliers – particularly for raw materi- als – successful companies are established worldwide ranging from East Asia (e.g., Tokyo Chemical Industry Co. Ltd. (Japan) or the Luminescence Technology Corporation (Taiwan)) to Europe and Australia (e.g., Greatcell Energy Pty. Ltd (Australia) or Dyenamo AB (Sweden)).121–124 For an extended list of companies that were identified to working in the field, the reader is referred to Table S5 in the ESI.† When it comes to the deposition techniques that companies target to employ for the industrial scale deposition of perovs- kite materials, this industry outlook reveals a strong interest in vapor phase deposition processes worldwide (see Fig. 5a). In stark contrast to the previously discussed heavy focus of scientific publications on solution processing, around 40% of all identified module manufacturers and 70% of all equipment manufacturers stated activities in vapor phase deposition or combinations of vapor phase deposition and solution proces- sing for the scalable processing of perovskite thin films. The interest in vapor phase deposition processes is manifested in all large industry clusters worldwide (East Asia, Europe, and North America). Furthermore, among the established solar module manufacturers, i.e., those solar module manufacturers This journal is © The Royal Society of Chemistry 2024Energy Environ. Sci., 2024, 17, 1645–1663 | 1657Open Access Article. Published on 23 January 2024. Downloaded on 6/14/2026 8:54:19 AM. This article is licensed under a Creative Commons Attribution 3.0 Unported Licence.View Article OnlinePerspective Energy & Environmental Science that already have a significant production capacity in place, the importance of vapor phase deposition processes is even stron- ger. Out of the 15 world-largest solar module manufacturers by annual production capacity (i.e., in the silicon and CdTe busi- ness), seven companies have been identified to actively work on perovskite PV, with six companies evaluating either vapor phase processing or a combination of vapor phase and solution processing. The motivation of these major players to rely nearly excl

  Keywords: deposition companies vapor phase module manufacturers perovskite worldwide industry solar processing techniques equipment established energy
• Vapor phase deposition of perovskite photovoltaics: short track to commercialization? (2024) · doi

  Can vapor phase deposition of perovskite thin films be a short track to a successful commercialization of perovskite PV? Here, we highlight the conceptional advantages of vapor phase pro- cessing and rationalize why we believe a stronger focus on these methods is pivotal for of the commercialization of perovskite PV. Worldwide, perovskite PV is progressing rapidly toward commercialization, with the first solar module manufacturers expected to enter the market by 2024/2025. Despite this rapid progress, it is yet unknown which fabrication technology – solution-based, vapor-based, or combinations – will eventually pave the way toward the economic breakthrough at the tera- watts scale. Today, all major global technology clusters, i.e., North America, Europe, and East Asia, encompass stakeholders with a focus on solution-based as well as vapor-based proces- sing of perovskite thin films. This perspective highlights the tremendous technological and economical potential of vapor phase deposition of perovs- kite thin films for PV manufacturing at industrial scale. The prime archetype for scalable, high-yield, and high-throughput perovskite PV manufacturing is the established thin-film PV industry (e.g., CdTe, CIGS, as well as organic PV and OLED industry), which is widely based on vapor phase processing. It is therefore not surprising, that also for perovskite-based PV a notable interest from industry on vapor-based deposition is again observed. The interest is particularly driven by recent advances in performance of vapor-based perovskite solar cells with certified PCEs up to 24.1%, which continue to close the gap to their solution-processed counterparts. A large variety of different vapor phase processes have been explored in research, including co-evaporation, sequential evaporation, and hybrid processing methods. Compared to their solution-based coun- terparts, vapor phase processes stand out due to their solvent- free, homogeneous, and pinhole-free deposition on planar and textured substrates. The latter is particularly critical for the manufacturing of monolithic tandem solar cells in combi- nation with textured silicon, which are expected to become the first commercial perovskite product with major market share. While it is often claimed that solution-based processing promises lower production and lower capital expenditure costs, for high our basic techno-economic analysis reveals that deposition rates and large-scale manufacturing tools, vapor phase processing can compete with solution processing in both categories, provided that key challenges of vapor processing are solved: first, state-of-the-art performance with respect to effi- ciency and durability needs to be achieved, motivating further research efforts with respect to perovskite compositions, charge transport layers, passivation strategies, and device architec- tures. Second, high-rate vapor phase processes (particularly for the organic halides) need to be developed that speed up the deposition by at least one to two orders of magnitude. To date, sequential vapor-phase processes may offer the highest, however, still too slow dynamic deposition rates. Research on new high-rate deposition concepts like closed-space sublimation, flash sublima- tion, or sputtering approaches as well as the exploration of industrial designs for evaporation sources has just started and needs to be emphasized. Finally, in order to enable high-yield and large-scale production, efficient and robust process regimes need to be identified and methods for reliable monitoring developed. In this regard, a better understanding of the evaporation char- acteristics of the precursor materials and the thin-film formation 1658 | Energy Environ. Sci., 2024, 17, 1645–1663This journal is © The Royal Society of Chemistry 2024Open Access Article. Published on 23 January 2024. Downloaded on 6/14/2026 8:54:19 AM. This article is licensed under a Creative Commons Attribution 3.0 Unported Licence.View Article OnlineEnergy & Environmental Science

  Keywords: vapor perovskite based phase deposition solution high processing thin scale manufacturing processes evaporation films commercialization