As perovskite solar cells (PSCs) are highly efficient, demonstration of high‐performance printed devices becomes important. 2D/3D heterostructures have recently emerged as an attractive way to relieving the film inhomogeneity and instability in perovskite devices. In this work, a 2D/3D ensemble with 2D perovskites self‐assembled atop 3D methylammonium lead triiodide (MAPbI3) via a one‐step printing process is shown. A clean and flat interface is observed in the 2D/3D bilayer heterostructure for the first time. The 2D perovskite capping layer significantly suppresses nonradiative charge recombination, resulting in a marked increase in open‐circuit voltage (VOC) of the devices by up to 100 mV. An ultrahigh VOC of 1.20 V is achieved for MAPbI3 PSCs, corresponding to 91% of the Shockley–Queisser limit. Moreover, notable enhancement in light, thermal, and moisture stability is obtained as a result of the protective barrier of the 2D perovskites. These results suggest a viable approach for scalable fabrication of highly efficient perovskite solar cells with enhanced environmental stability.
The concept of mixed 2D/3D heterostructures has emerged as an effective method for improving the stability of lead halide perovskite solar cells, which has been, however, rarely reported in lead–tin (Pb–Sn) mixed perovskite devices. Here, we report a scalable process for depositing mixed 2D/3D Pb–Sn perovskite solar cells that deliver remarkably enhanced efficiency and stability compared to their 3D counterparts. The incorporation of a small amount (3.75%) of an organic cation 2-(4-fluorophenyl)ethylammonium iodide induces the growth of highly oriented Pb–Sn perovskite crystals perpendicularly aligned with the substrate. Moreover, for the first time, phase segregation is observed in pristine 3D Pb–Sn perovskites, which is suppressed due to the presence of the 2D perovskites. Accordingly, a high current density of 28.42 mA cm–2 is obtained due to the markedly enhanced spectral response and charge extraction. Eventually, mixed 2D/3D Pb–Sn perovskite devices with a band gap of 1.33 eV yield efficiencies as high as 17.51% and in parallel exhibit good stability.
Metal halide perovskite solar cells (PSCs) have raised considerable scientific interest due to their high cost‐efficiency potential for photovoltaic solar energy conversion. As PSCs already are meeting the efficiency requirements for renewable power generation, more attention is given to further technological barriers as environmental stability and reliability. However, the most major obstacle limiting commercialization of PSCs is the lack of a reliable and scalable process for thin film production. Here, a generic crystallization strategy that allows the controlled growth of highly qualitative perovskite films via a one‐step blade coating is reported. Through rational ink formulation in combination with a facile vacuum‐assisted precrystallization strategy, it is possible to produce dense and uniform perovskite films with high crystallinity on large areas. The universal application of the method is demonstrated at the hand of three typical perovskite compositions with different band gaps. P‐i‐n perovskite solar cells show fill factors up to 80%, underpinning the statement of the importance of controlling crystallization dynamics. The methodology provides important progress toward the realization of cost‐effective large‐area perovskite solar cells for practical applications.
Halide perovskites are one of the ideal photovoltaic materials for constructing flexible solar devices due to relatively high efficiencies for low‐temperature solution‐processed devices. However, the overwhelming majority of flexible perovskite solar cells are produced using spin coating, which represents a major hurdle for upscaling. Here, a scalable approach is reported to fabricate efficient and robust flexible perovskite solar cells on a polymer substrate. Thiourea is introduced into perovskite precursor solution to modulate the crystal growth, resulting in dense and uniform perovskite thin films on rough surfaces. As a decisive step, a cascade energy alignment is realized for the hole extraction layer by rationally designing a bilayer interface comprised of PEDOT:PSS/PTAA with a distinct offset in the highest occupied molecular orbital levels, enabling markedly enhanced charge extraction and spectral response. An efficiency as high as 19.41% and a record fill factor up to 81% are achieved for flexible perovskite devices processed by a scalable printing method. Equally important, the bilayer interface reinforces the bendability of the indium tin oxide substrate, leading to enhanced mechanical robustness of the flexible devices. These results underpin the importance of morphology control and interface design in constructing high‐performance flexible perovskite solar cells.
Sequential deposition is demonstrated as an effective technology for preparation of high-performance perovskite solar cells based on lab-scale spin coating. However, devices fabricated by scalable methods are lagging far behind their state-of-the-art spin-coated counterparts, largely due to the difficulty in obtaining high-quality thin films of perovskites crystallized from printed precursors. Here, a generic strategy that allows sequential deposition of dense and uniform perovskite films via two-step blade coating is reported. The rational selection of solvent combined with a mild vacuum extraction process enables us to produce uniform lead iodide (PbI 2 ) films over large areas. Significantly, the resulting PbI 2 films possess a mesoporous structure that is highly beneficial for the insertion reaction with methylammonium iodide (MAI). It is further identified that the deposition temperature of MAI plays an important role in determining the morphology and crystallinity of the perovskite films. Solar cells using these sequentially bladed perovskite layers yield efficiencies over 16% with high fill factors up to 78%. These results represent important progress toward the largescale deposition of perovskite thin films for practical applications. Photovoltaic Perovskite Layers
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