Layer‐by‐layer (LBL) deposition strategy enabling favorable vertical phase distributions has been regarded as promising candidates for constructing high‐efficient organic photovoltaic (OPV) cells. However, solid additives with the merits of good stability and reproducibility have been rarely used to fine‐tune the morphology of the LBL films for improved efficiency and stability. Herein, hierarchical morphology control in LBL OPV is achieved via a dual functional solid additive. Series of LBL devices are fabricated by introducing the solid additive individually or simultaneously to the donor or acceptor layer to clarify the functions of additives. Additive in the donor layer can facilitate the formation of preferable vertical component distribution, and that in the acceptor layer will enhance the molecular crystallinity for better charge transport properties. The optimized morphology ultimately contributed to high PCEs of 16.4% and 17.4% in the binary and quaternary LBL devices. This reported method provides an alternative way to controllably manipulate the morphology of LBL OPV cells.

Low work-function metal oxides have been widely used as electron transport layer (ETL) in organic solar cells (OSCs). However, the ubiquitous contact barrier and intrinsic surface defects of such ETLs...

The last decades have witnessed the rapid development and the gradually improved efficiencies of organic solar cells (OSCs), which show great potentials in the fabrication of eco-friendly and flexible photovoltaic panels. Layer-by-layered (LBL) structure via sequential processing of the donor and acceptor layers becomes an advisable option to construct pseudo-bilayer configurations in OSC active layer. Favorable vertical phase separation and sufficient exciton dissociation interfaces can be simultaneously realized in such aggregation morphology via different processing technologies and strategies. High efficiencies of over 18% in ternary LBL device and 11.9% in LBL-processed module (11.52 cm 2 ) have been successfully achieved in recent works. Moreover, the unique merits of LBL structure in individual layer processing enable it a promising candidate for large-scale printing and further industrialization of OSCs. This perspective provides the recent advance of LBL OSCs with the focus on fabrication technologies and strategies for morphology control and also proposes the current thinking and perspective on LBL structures for future development.

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as a potential green energy-generating technology, proving to be a game-changer in photovoltaics. [1][2][3] Significant efforts, including material design, thin-film growth control, and interface engineering, have been devoted to promoting device performance. [4][5][6] Within only a few years, the power conversion efficiencies (PCEs) of single-junction PerSCs have been enhanced to 20% threshold. [7][8][9][10] Despite the leaps and bounds in efficiency, the stability of PerSCs, especially moisture/ water and thermal stability, is still a severe concern, since a long-term environmental atmosphere potentially makes degradation or phase transition of the perovskite. [11][12][13] Accordingly, device instability issues must be overcome along with the improvement of the PCE of PerSCs.Interface and grains control plays a vital role in achieving highly efficient and stable PerSCs. Nonradiative recombination caused by traps/defects existing at the interface and grain boundaries (GBs) impairs charge-density buildup and diminishes the photo-voltage of devices. [14][15][16] Moreover, these defects are the attack points of external factors such as water and thermal, resulting in the decomposition of perovskite. [17,18] Uncoordinated Pb 2+ ion is one typical ion defect on the surface and GBs of perovskite which seriously injures the device performance. [19] Previous studies have been carried out toward solving uncoordinated Pb 2+ ions in achieving high-efficiency PerSCs. [20] A series of organic molecules containing lone pair electrons on oxygen, sulfur, or nitrogen (such as pyridine, thiophene, benzoquinone, and crown ether) have been selected to reduce those defect sites by coordination bonds. [21][22][23] For instance, a series of crown ethers were employed to suppress uncoordinated surface defects, yielding an improved PCE exceeding 23% and achieving enhanced stability under ambient and operational conditions. [24] Moreover, as for the n-i-p structured PerSCs, SnO 2 has been regarded as a promising candidate for electron transport material. [25] However, surface traps/defects existing at the SnO 2 / perovskite interface are disadvantageous for charge transport. Therefore, optimizing the SnO 2 /perovskite interface to suppress the formation of surface traps/defects is vital to boosting device performance. [26,27] Generally, further modificationThe organic-inorganic halide perovskite solar cell (PerSC) is the state-of-theart emerging photovoltaic technology. However, the environmental water/ moisture and temperature-induced intrinsic degradation and phase transition of perovskite greatly retard the commercialization process. Herein, a dual-functional organic ligand, 4,7-bis((4-vinylbenzyl)oxy)-1,10-phenanthroline (namely, C1), with crosslinkable styrene side-chains and chelatable phenanthroline backbone, synthesized via a cost-effective Williamson reaction, is introduced for collaborative electrode interface and perovskite grain boundaries (GBs) engineering. C1 can chemically chelate with Sn 4+ in the SnO 2 electron transport...