In the past two decades, reversible data hiding (RDH), also referred to as lossless or invertible data hiding, has gradually become a very active research area in the field of data hiding. This has been verified by more and more papers on increasingly wide-spread subjects in the field of RDH research that have been published these days. In this survey paper the various RDH algorithms and researches have been classified into the following six categories: 1) RDH into image spatial domain, 2) RDH into image compressed domain (e.g., JPEG), 3) RDH suitable for image semi-fragile authentication, 4) RDH with image contrast enhancement, 5) RDH into encrypted images, which is expected to have wide application in the cloud computation, and 6) RDH into video and into audio. For each of these six categories, the history of technical developments, the current state of the arts, and the possible future researches are presented and discussed. It is expected that the RDH technology and its applications in the real word will continue to move ahead.

Despite the remarkable performance progress being made, environmental concerns remain for lead halide perovskite solar cells (PSCs) because of the possible water dissolution of lead ions (Pb2+) into the environment. Herein, we succeed in mitigating Pb leakage of PSCs, for the first time, via implanting in situ polymerized networks into perovskites. We strategically transform the dormant monomer additives into chelating polymer networks within perovskite layers, which not only passivate the defects of perovskite but also protect Pb2+ from water dissolution. The resultant perovskite–polymer hybrids have successfully enabled state-of-art power conversion efficiencies (PCEs) for inverted PSCs (PCE of 22.1%) and large-area modules (PCE of 15.7%). More importantly, up to 94% rejection rate of Pb2+ dissolution is achieved upon directly immersing the unencapsulated devices into water, which reasonably simulates the exposure of the broken and unprotected panels to torrential rain for 24 h.

performance, superior flexibility, vivid colors, unique transparency, potential lowcost production with solution processing, etc. [1][2][3][4][5][6][7][8][9] The recent years have witnessed a great leap in device performance and device stability, which are attributed to the delicate molecular structure design, advanced morphology manipulation technology, and device structure evolution. [10][11][12][13][14][15][16][17][18][19] Currently, the best-performed OPVs exhibit a certified efficiency of 19.3% for single junction device and 20.0% for tandem structure, as well as an extrapolated device stability with T 80 over 30 years. [20][21][22] While compared to their inorganic counterparts (e.g., for siliconbased PVs, the efficiency is over 26%), the OPVs are still inferior in efficiency. [23] Therefore, it would be urgent to further improve the device efficiency of OPV, which will require an in-depth understanding on the working principles of OPV, as well as the development of effective strategies to balance the charge generation, transport, and recombination. Among all the strategies, it is generally observed that adding a third component to construct the ternary blend is a very simple but effective method to further boost the device performance of OPVs. [24][25][26][27][28][29][30][31][32] A bunch of benefits have been demonstrated with the multicomponentThe ternary blend is demonstrated as an effective strategy to promote the device performance of organic photovoltaics (OPVs) due to the dilution effect. While the compromise between the charge generation and recombination remains a challenge. Here, a mixed diluent strategy for further improving the device efficiency of OPV is proposed. Specifically, the high-performance OPV system with a polymer donor, i.e., PM6, and a nonfullerene acceptor (NFA), i.e., BTP-eC9, is diluted by the mixed diluents, which involve a high bandgap NFA of BTP-S17 and a low bandgap NFA of BTP-S16 (similar with that of the BTP-eC9). The BTP-S17 of better miscibility with BTP-eC9 can dramatically enhance the open-circuit voltage (V OC ), while the BTP-S16 maximizes the charge generation or the short-circuit current density (J SC ). The interplay of BTP-17 and BTP-S16 enables better compromise between charge generation and recombination, thus leading to a high device performance of 19.76% (certified 19.41%), which is the best among single-junction OPVs. Further analysis on carrier dynamics validates the efficacy of mixed diluents for balancing charge generation and recombination, which can be further attributed to the more diverse energetic landscapes and improved morphology. Therefore, this work provides an effective strategy for highperformance OPV for further commercialization.

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