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Abstract: Simultaneously optimizing the processing parameters of functional thin films remains a challenge. The design and utilization of a fully automated platform called SPINBOT is presented for the engineering of solution‐processed functional thin films. The SPINBOT is capable of performing experiments with high sampling variability through the unsupervised processing of hundreds of substrates with exceptional experimental control. Through the iterative optimization process enabled by the Bayesian optimization (BO) algorithm, the SPINBOT explores an intricate parameter space, continuously improving the quality and reproducibility of the produced thin films. This machine learning (ML)‐guided reliable SPINBOT platform enables the acceleration of the optimization process of perovskite solar cells via a simple photoluminescence characterization of films. As a result, this study arrives at an optimal film that, when processed into a solar cell in an ambient atmosphere, immediately yields a champion power conversion efficiency (PCE) of 21.6% with satisfactory performance reproducibility. The unsealed devices retain 90% of their initial efficiency after 1100 h of continuous operation at 60–65 °C under metal‐halide lamps. It is anticipated that the integration of robotic platforms with the intelligent algorithm will facilitate the widespread adoption of effective autonomous experimentation to address the evolving needs and constraints within the materials science research community.

Suppressing deep-level defects at the perovskite bulk and surface is indispensable for reducing the non-radiative recombination losses and improving efficiency and stability of perovskite solar cells (PSCs). In this study, two Lewis bases based on chalcogen-thiophene (n-Bu4S) and selenophene (n-Bu4Se) having tetra-pyridine as bridge are developed to passivate defects in perovskite film. The uncoordinated Pb2+ and iodine vacancy defects can interact with chalcogen-concave group and pyridine group through the formation of the Lewis acid-base adduct, particularly both the defects can be surrounded by concave molecules, resulting in effective suppression charge recombination. This approach enables a power conversion efficiency (PCE) as high as 25.37% (25.18% certified) for n-i-p PSCs with stable operation at 65 °C and 1-sun illumination for 1300 hours in N2 (ISOS-L-2 protocol), retaining 94% of the initial efficiency. Our work provides insight into the bowl-shaped Lewis base in defects passivation by coordinated strategy for high-performance photovoltaic devices. Suppressing deep-level defects at the perovskite bulk and surface is critical to reduce the non-radiative recombination losses in perovskite solar cells. Here, authors employ concave-shaped chalcogen molecules for defect passivation, achieving certified efficiency of 25.18% for stable n-i-p devices. [ABSTRACT FROM AUTHOR]

Upscaling the coating of formamidinium lead triiodide (FAPbI3) thin film is essential to realizing full printing and thereby roll‐to‐roll production of perovskite photovoltaics. However, thin‐film FAPbI3 processed from antisolvent‐free, printing methods suffer from undesirable degradation to the non‐photoactive phase, particularly in ambient processing conditions. Here, the most critical stage in thin‐film processing is identified as the gas‐quenching treatment of the as‐cast wet film. It is crucial to achieve both the nucleation of α‐phase nanocrystals and their sufficient growth at room temperature, which are indispensable for templating the growth of a highly crystalline and stable α‐FAPbI3 film during subsequent thermal annealing. The gas‐quenching‐treated film without these α‐phase nanocrystals can only be converted to meta‐stable α‐FAPbI3 by thermal annealing. By precisely identifying the spontaneous doping of cesium ion (Cs+) as a key factor in triggering α‐FAPbI3 nucleation and the role of chloride ion (Cl−) in enhancing nanocrystal growth, a generalized mechanism for additive engineering for the precursor ink is theorized. The identified mechanism translates to a power conversion efficiency of 19.36% for fully printed carbon‐electrode solar cells, 16.23% for carbon‐electrode minimodules, and excellent operational stability, showing the promising potential of this proposed fabrication route in the upscaling of perovskite photovoltaics. [ABSTRACT FROM AUTHOR]

Lithium bis(trifluoromethane)sulfonimide (Li-TFSI) is extensively employed as a p-type dopant to enhance the conductivity of hole-transporting materials (HTMs) in n–i–p perovskite solar cells (PSCs). Despite its effectiveness, the hygroscopic and migratory nature of Li-TFSI compromise the long-term stability of PSCs. Herein, a new p-type dopant, namely, lithium tetrakis(pentafluorophenyl)borate (Li-BCF), was constructed for use in a poly[bis(4-phenyl)(2,4,6-trimethylphenyl)amine] (PTAA)-based PSC by replacing the anion unit TFSI− of Li-TFSI with the fluorinated boric acid anion BCF−. It was found that the BCF− anion has stronger interactions with Li+ and PTAA˙+ compared with the TFSI− anion, resulting in weakened moisture absorption and migration of Li+ as well as improved doping stability of the PTAA:Li-BCF combination when subjected to elevated temperatures up to 85 °C. With this anionic engineering, a fabricated Li-BCF-doped PTAA-based device achieved improved efficiency and retained 95% of its initial power conversion efficiency during 1000 h of one-sun operation at its maximum power point (ISOS-L-1), yielding up to a 12-fold increase in T80 operational lifetime. Our findings provide valuable insights for the future design of p-type dopants and for their optimized use in photovoltaic applications. [ABSTRACT FROM AUTHOR]

High-performance wide-bandgap (WBG) perovskite solar cells are used as top cells in perovskite/silicon or perovskite/perovskite tandem solar cells, which possess the potential to overcome the Shockley-Queisser limitation of single-junction perovskite solar cells (PSCs). However, WBG perovskites still suffer from severe nonradiative recombination and large open-circuit voltage (Voc) losses, which restrict the improvement of PSC performance. Herein, we introduce 3,3'-diethyl-oxacarbo-cyanine iodide (DiOC2(3)) and multifunctional groups (C=N, C=C, C-O-C, C-N) into perovskite precursor solutions to simultaneously passivate deep level defects and reduce recombination centers. The multifunctional groups in DiOC2(3) coordinate with free Pb2+ at symmetric sites, passivating Pb vacancy defects, effectively suppressing nonradiative recombination, and maintaining considerable stability. The results reveal that the power conversion efficiency (PCE) of the 1.68 eV WBG perovskite solar cell with an inverted structure increases from 18.51% to 21.50%, and the Voc loss is only 0.487 V. The unpackaged device maintains 95% of its initial PCE after 500 h, in an N2 environment at 25°C. [ABSTRACT FROM AUTHOR]

Li-TFSI/tBP is a classic doping system for the hole transport materials in efficient perovskite solar cells (PSCs), but the ultra-hygroscopicity and Li+ migration of Li-TFSI, the volatility of tBP, and the polarity of acetonitrile promoting the solubility of Li-TFSI in chlorobenzene have negative impacts on the performances of PSCs. Herein, by replacing the hygroscopic Li+ in Li-TFSI with a benzene ring, we developed a novel non-ionic p-dopant (N-phenyl-bis(trifluoromethanesulfonimide)), (Ph-TFSI), which solves the above problems existing in the Li TFSI/tBP doping system due to the absence of hygroscopic Li+ and good solubility in chlorobenzene. In addition, owing to the lower HOMO energy level of Ph-TFSI, it can accept electrons from PTAA to generate [PTAA]+ radicals for effective doping without post-treatment of oxygen and light. PSCs based on Ph-TFSI doped PTAA achieved an efficiency of 21.82%, which is better than those of PSCs based on Li-TFSI/tBP doped PTAA (20.11%). Furthermore, due to the absence of hygroscopic Li+, tBP and acetonitrile, the long-term stability of PSCs based on Ph-TFSI doped PTAA is significantly improved, retaining 88% of the initial efficiency after 30 days of exposure in air, while PSCs based on Li-TFSI/tBP doped PTAA only maintains 63% of the initial efficiency under the same aging conditions. Finally, the universality of Ph-TFSI was studied by doping another classic hole transport material Spiro-OMeTAD. The results showed that Ph-TFSI can also effectively dope Spiro-OMeTAD, and the corresponding PSC achieved good device performance. [ABSTRACT FROM AUTHOR]

Mixed lead and tin (Pb/Sn) hybrid perovskites exhibit a great potential in fabricating all‐perovskite tandem devices due to their easily tunable bandgaps. However, the energy deficit and instability in Pb/Sn perovskite solar cells (PSCs) constrain their practical applications, which renders defect passivation engineering indispensable to develop highly efficient and long‐term stable PSCs. Herein, the mechanisms of strain tailoring and defect passivation in Pb/Sn PSCs by 2D ligands are investigated. The 2D ligands include electroneutral cations with long alkyl chain (LAC), iodates with relatively short alkyl chain (SAC) and their mixtures. This study reveals that LAC ligands facilitate the relaxation of tensile strain in perovskite films while SAC ligands cause strain buildup. By mixing LAC/SAC ligands, tensile strain in perovskite films can be balanced which improves solar cell performance. PSCs with admixed β‐guanidinopropionic acid (GUA)/phenethylammonium iodide (PEAI) exhibit enhanced open circuit voltage and fill factor, which is attributed to reduced nonradiative recombination losses in the bulk and at the interfaces. Furthermore, the operational stability of PSCs is slightly improved by the mixed 2D ligands. This work reveals the mechanisms of 2D ligands in strain tailoring and defect passivation toward efficient and stable narrow‐bandgap PSCs. [ABSTRACT FROM AUTHOR]