Inverted perovskite solar cells (PSCs) with low‐temperature processed hole transporting materials (HTMs) suffer from poor performance due to the inferior hole‐extraction capability at the HTM/perovskite interfaces. Here, molecules with controlled electron affinity enable a HTM with conductivity improved by more than ten times and a decreased energy gap between the Fermi level and the valence band from 0.60 to 0.24 eV, leading to the enhancement of hole‐extraction capacity by five times. As a result, the 3,6‐difluoro‐2,5,7,7,8,8‐hexacyanoquinodimethane molecules are used for the first time enhancing open‐circuit voltage (Voc) and fill factor (FF) of the PSCs, which enable rigid‐and flexible‐based inverted perovskite devices achieving highest power conversion efficiencies of 22.13% and 20.01%, respectively. This new method significantly enhances the Voc and FF of the PSCs, which can be widely combined with HTMs based on not only NiOx but also PTAA, PEDOTT:PSS, and CuSCN, providing a new way of realizing efficient inverted PSCs.
Instability of rear electrodes undermines the long-term operational durability of efficient perovskite solar cells (PSCs). Here, a composite electrode of copper-nickel (Cu-Ni) alloy stabilized by in situ grown bifacial graphene is designed. The alloying makes the work function of Cu suitable for regular PSCs and Cu-Ni is the ideal substrate for preparing high-quality graphene via chemical vapor deposition, which simultaneously protects the device from oxygen, water and internal components reaction. To rivet the composite electrode with semi-device, a thermoplastic copolymer is employed as an adhesive layer during hot pressing. The resultant device achieved power conversion efficiency of 24.34% with significantly improved stability; the devices without encapsulation retained 97% of their initial efficiency after the damp heat test at 85 o C with relative humidity of 85% for 1440 hours and the encapsulated devices maintained 95% of their initial efficiencies after maximum power point tracking under continuous 1 sun illumination for 5000 hours.Metal halide perovskite solar cells (PSCs) have attracted great attention in both academia and industry owing to their excellent optoelectronic performance and low manufacturing costs 1-6 . However, for PSCs to realize commercialization, they must survive the long-term natural erosion imposed by oxygen, moisture, light and heat 7,8 . Thanks to the optimization of the perovskite materials, charge transport materials and the interface layers 9-12 , the
Lead‐free tin perovskite solar cells (TPSCs) have attracted widespread attention in recent years due to their low toxicity, suitable bandgap, and high carrier mobility. However, the photovoltage and efficiency of TPSCs are still much lower than those of the lead counterparts because of the high trap density and unfavorable band structure in tin perovskite films. To overcome these issues, efficient and stable TPSCs with a graded heterostructure of light‐absorbing layer are reported, in which the narrow‐bandgap tin perovskite dominates at the bulk, whereas the wide‐bandgap tin perovskite is distributed with a gradient from bulk to surface. This heterostructure can selectively extract the photogenerated charge carriers at the perovskite/electron transport layer interface, reduce the density of trap states, and impede the oxidation process of Sn2+ to Sn4+ in air. As a consequence, this graded heterostructure of tin perovskite layer contributes to an increase of 120 mV in the open‐circuit voltage and a maximum power conversion efficiency of 11% for TPSCs with longer operational stability.
Tin halide perovskites are promising candidates for preparing efficient leadfree perovskite solar cells due to their ideal band gap and high charge-carrier mobility. However, the notorious rapid crystallization process results in the inferior power conversion efficiency (PCE) of tin perovskite solar cells (TPSCs). Here, a facile method is employed to manage this crystallization process by using cold precursor solution that raises the critical Gibbs free energy to slow down the nucleation rate, sparing both space and time for crystal growth. In this way, highly oriented FASnI 3 films with micrometer-scale grains are fabricated and an increase of 70 mV in the open-circuit voltage is obtained for TPSCs. This method is compatible with other existed strategies such as additive engineering or the post-treatment method. The best-performing device that combines 0 °C precursor solution and post-treatment method demonstrates a PCE of 12.11%.
Languages using Chinese characters are mostly processed at word level. Inspired by recent success of deep learning, we delve deeper to character and radical levels for Chinese language processing. We propose a new deep learning technique, called "radical embedding", with justifications based on Chinese linguistics, and validate its feasibility and utility through a set of three experiments: two in-house standard experiments on short-text categorization (STC) and Chinese word segmentation (CWS), and one in-field experiment on search ranking. We show that radical embedding achieves comparable, and sometimes even better, results than competing methods.
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