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In a recent paper published in Energy & Environmental Science, Ávila et al. report a fully vacuum-processed dual-junction CH₃NH₃PbI₃/CH₃NH₃PbI₃ tandem solar cell featuring an unprecedentedly high open-circuit voltage of 2.30 V. This work demonstrates the promise of vacuum-based process for fabricating light-weight and flexible all-perovskite tandem solar cells with ultra-high power-conversion efficiencies.

The instability of the 3D α phase of narrow-bandgap inorganic perovskites such as CsPbI₃ and CsPbI₂Br limits the development of inorganic PSCs. We found that europium doping of the all-inorganic CsPbI₂Br perovskite results in stabilization of its black photoactive phase and significant improvement of its photovoltaic performance. Applying solid-state magic-angle spinning nuclear magnetic resonance, we show for the first time that europium is incorporated as B cation into the perovskite lattice on the atomic level, making it a promising modulator of the intrinsic material properties. Electroluminescence and time-resolved photoluminescence decay measurements show that incorporation of europium suppresses non-radiative charge-carrier recombination by eliminating tail states, which explains the resulting high open-circuit voltage of 1.27 V.

All-inorganic perovskite films hold promise for improving the stability of perovskite solar cells (PSCs). However, the 3D α phase of narrow-bandgap inorganic perovskites is thermodynamically unstable at room temperature, limiting the development of high-performance inorganic PSCs. Here, we show that europium doping of CsPbI₂Br stabilizes the α phase of this inorganic perovskite at room temperature. We rationalize it by using solid-state nuclear magnetic resonance and high-angle annular dark-field scanning transmission electron microscopy, which show that europium is incorporated into the perovskite lattice. We demonstrate a maximum power-conversion efficiency of 13.71% for an inorganic PSC with the CsPb_0.95Eu_0.05I₂Br perovskite and a stable power output of 13.34%. Using electroluminescence we show that incorporation of europium reduces non-radiative recombination, resulting in high open-circuit voltage of 1.27 V. The devices retain 93% of the initial efficiency after 370 hr under 100 mW cm⁻² continuous white light illumination under maximum-power point-tracking measurement.

Organic-inorganic hybrid perovskites have been proven to be multifunctional semiconductors with wide applications. Devices using 3D perovskites exhibit extremely high PCE and can be fabricated with low-cost solution process. After replacing the small organic cations with long-chain organic molecules, the 3D crystal lattice will expand into a 2D structure; these 2D materials have been successfully applied in thin-film transistors and light-emitting diodes. In this work, 3D-2D planar perovskite-perovskite heterojunctions (PPPHs) were constructed by a facile slight solvent-assisted interfacial reaction (SSAIR) using a BAI solution to treat MAPbI₃. By applying these PPPHs in solar cells with modified electrical engineering, it is possible to not only remove the expensive organic hole transport layer but also achieve improved moisture, thermal, and illumination stability. Besides energy harvesting, the PPPH structure also shed light on the design and realization of other opto-electrical devices.

The expensive and unstable organic hole transport layer (HTL) is one of the crucial problems that hampers the wide application of perovskite solar cells. Here, an MAPbI₃-(BA)₂(MA)_n−1Pb_nI_3n+1 3D-2D perovskite-perovskite planar heterojunction (PPPH) through a facile BAI and MAPbI₃ interfacial ion exchange process was conducted. A graded band structure was formed for efficient charge separation, and the conductivity of the 2D perovskite can be tuned by extrinsic FA incorporation, which provides effective conducting channels for holes, making the modified 2D perovskite layer a promising and stable HTL. Optimized solar cells based on 3D-2D PPPH showed a champion power conversion efficiency (PCE) of 13.15% initially and 16.13% after thermal aging, and could maintain 71% output for 50 days under 65% humidity, and 74% for 30 days under 85°C, without encapsulation. This work points to realize low cost and ambient compatible PPPH solar cells with high PCE and robust stability.

The efficiency of organic-inorganic halide perovskite solar cells skyrocketed in the past 6 years, reaching 23.3%. Their pairing with silicon in tandem solar cells offers a promising path for further reducing the levelized cost of electricity of photovoltaics. Strategies such as compositional engineering and charge-transport-layer optimization have been reported to improve the tandem efficiency. However, the large open-circuit voltage deficit of wide-bandgap perovskite cells still limits the tandem performance. Here, we utilize combined additives to smooth the perovskite film, increase its grain size, and lower its defect density. The synergistic effect of the additives leads to increased photocurrent and reduced open-circuit voltage deficit for wide-bandgap perovskite solar cells. When additives are used to form a top cell with a bandgap of 1.64 eV, the perovskite and silicon sub-cells are current matched and yield a perovskite/silicon tandem device with an efficiency of 25.4%.

Organic-inorganic halide perovskites are promising semiconductors to mate with silicon in tandem photovoltaic cells due to their solution processability and tunable complementary bandgaps. Herein, we show that a combination of two additives, MACl and MAH₂PO₂, in the perovskite precursor can significantly improve the grain morphology of wide-bandgap (1.64–1.70 eV) perovskite films, resulting in solar cells with increased photocurrent while reducing the open-circuit voltage deficit to 0.49–0.51 V. The addition of MACl enlarges the grain size, while MAH₂PO₂ reduces non-radiative recombination through passivation of the perovskite grain boundaries, with good synergy of functions from MACl and MAH₂PO₂. Matching the photocurrent between the two sub-cells in a perovskite/silicon monolithic tandem solar cell by using a bandgap of 1.64 eV for the top cell results in a high tandem V_oc of 1.80 V and improved power conversion efficiency of 25.4%.

Recently, tin perovskite solar cells (PSCs) have attracted a great deal of research interest due to their low toxicity, ideal band gap, and earth-abundant elements. However, the poor stability and high density of defects severely limit the performance of tin PSCs. The incorporation of low-dimensional perovskite with molecule-protecting layers is vital to overcome the obstacles. Herein, we demonstrate a hierarchy structure tin perovskite induced by the removable pseudohalogen regulator NH₄SCN. The hierarchy structure comprising highly parallel-orientation 2D-quasi-2D-3D FASnI₃ significantly enhances stability and oxidation resistance. We then explored the hierarchy structure PSCs and achieved a PCE up to 9.41% with high reproducibility. This work suggests an effective strategy to build tin PSCs with high performance and long-term stability.

The power conversion efficiency (PCE) of tin perovskite solar cells is impeded by the extremely poor resistance to oxidation and high density of intrinsic Sn vacancies. Herein, we grow a 2D-quasi-2D-3D Sn perovskite film using removable pseudohalogen NH₄SCN as a structure regulator. This hierarchy structure remarkably enhances air stability resulting from the parallel growth of 2D PEA₂SnI₄ as the surface layer. We then explore the hierarchy structure perovskite films in planar structural solar cells, which generate a PCE up to 9.41%. The device retains 90% of its initial performance for almost 600 hr. Our results suggest that adding removable NH₄SCN in a perovskite precursor can significantly improve the stability and photovoltaic performance of Sn perovskite. This finding provides a powerful strategy to manipulate the structure of low-dimensional perovskite in order to enhance the performance of perovskite solar cells.

Metal halide hybrid organic-inorganic perovskite solar cells have seen enormous research interest, with more than 10,000 papers published since the report of the first solid-state perovskite cells in 2012. Efficiencies have surpassed 20% in 2015. The major hurdles obviating commercialization are stability and scalability. In this context, we provide a framework bridging domains from economic modeling to materials science. Insights gained by in situ X-ray diffraction allow substitution of spin coating for blade coating and slow thermal annealing for rapid annealing, enabling scale-up without sacrificing cell performance. The high throughputs enabled by this processing route enable cost-effective production of perovskite solar cells, which can help to accelerate the shift to renewable energies.

Cost modeling shows that high-throughput processing of perovskite solar cells is required not only to compete with incumbent technologies in terms of levelized cost of energy, but more importantly, it is the major enabling factor facilitating sustainable growth rates of solar cell manufacturing capacity commensurate with global climate targets. We performed rapid thermal annealing at blade-coating speed to quickly deposit and convert perovskite thin films for scalable manufacturing of perovskite solar cells. In situ X-ray diffraction during film deposition and thermal conversion gave insight into the formation of crystalline intermediates, essential for high-quality films. Parameters were optimized based on the in situ study, allowing perovskite films to be annealed within 3 s with a champion power conversion efficiency of 16.8%. This opens up a clear pathway toward industrial-scale high-throughput manufacturing, which is required to fulfill the projected photovoltaic installation rates needed to reach climate goals.