OSCs have mainly employed bulk heterojunction (BHJ) structures in the photoactive layers, in which the blend casting (BC) of donor (D) and acceptor (A) materials can form interpenetrating networks with a large D/A interface area for exciton dissociation. However, it is challenging to delicately balance the self-aggregation and miscibility of the two components during the one-step deposition, involving complicated dynamic and kinetic processes. [12] Accordingly, the photovoltaic performances of BC devices depend strongly on the conditions of host solvents, [13] blending ratio of D:A, [14][15][16][17][18] processing additives, [19][20][21][22] and post-treatment. [23] Thus, it is difficult to control the film morphologies, especially the D/A distribution in the vertical direction of BC films, [12] which is closely related to the charge transport and collection.To tailor vertical phase distribution efficiently, the two-step deposition of D and A materials in a sequence, namely, the sequential deposition (SD) method, is considered as an alternative to the BC process. [24][25][26][27][28][29][30][31][32][33] Since the deposition of D and A can be performed independently, the SD OSCs offer unique advantages, including a favored vertical phase distribution and improved film morphology, which provides sufficient D/A interface area, and direct transport pathways for charge carriers. [34][35][36] Obviously, it is beneficial to exciton dissociation and chargeThe variation of the vertical component distribution can significantly influence the photovoltaic performance of organic solar cells (OSCs), mainly due to its impact on exciton dissociation and charge-carrier transport and recombination. Herein, binary devices are fabricated via sequential deposition (SD) of D18 and L8-BO materials in a two-step process. Upon independently regulating the spin-coating speeds of each layer deposition, the optimal SD device shows a record power conversion efficiency (PCE) of 19.05% for binary singlejunction OSCs, much higher than that of the corresponding blend casting (BC) device (18.14%). Impressively, this strategy presents excellent universality in boosting the photovoltaic performance of SD devices, exemplified by several nonfullerene acceptor systems. The mechanism studies reveal that the SD device with preferred vertical components distribution possesses high crystallinity, efficient exciton splitting, low energy loss, and balanced charge transport, resulting in all-around enhancement of photovoltaic performances. This work provides a valuable approach for high-efficiency OSCs, shedding light on understanding the relationship between photovoltaic performance and vertical component distribution.

The development of organic solar cells (OSCs) with thick active layers is of crucial importance for the roll-to-roll printing of large-area solar panels. Unfortunately, increasing the active layer thickness usually results in a significant reduction in efficiency. Herein, we fabricated efficient thick-film OSCs with an active layer consisting of one polymer donor and two non-fullerene acceptors. The two acceptors were found to possess enlarged exciton diffusion length in the mixed phase, which is beneficial to exciton generation and dissociation. Additionally, layer by layer approach was employed to optimize the vertical phase separation. Benefiting from the synergetic effects of enlarged exciton diffusion length and graded vertical phase separation, an efficiency of 17.31% (certified value of 16.9%) is obtained for the 300 nm-thick OSC, with a short-circuit current density of 28.36 mA cm−2, and a high fill factor of 73.0%. Moreover, the device with an active layer thickness of 500 nm also shows an efficiency of 15.21%. This work provides valuable insights into the fabrication of OSCs with thick active layers.

Although organic solar cells (OSCs) have delivered an impressive power conversion efficiency (PCE) of over 19 %, most of them demonstrated rather limited stability. So far, there are hardly any effective and universal strategies to improve stability of state-ofthe-art OSCs. Herein, we developed a hybrid electrontransport layer (ETL) in inverted OSCs using ZnO and a new modifying agent (NMA), and significantly improved the stability and PCEs for all the tested devices. In particular, when applied in the D18 : N3 system, its inverted OSC exhibits so far the highest PCE (18.20 %) among inverted single-junction OSCs, demonstrating an extrapolated T 80 lifetime of 7572 h (equivalent to 5 years under outdoor exposure). This is the first report with T 80 over 5000 h among OSCs with over 18 % PCE. Furthermore, a high PCE of 16.12 % can be realized even in a large-area device (1 cm 2 ). This hybrid ETL strategy provides a strong stimulus for highly prospective commercialization of OSCs.

Organic solar cells (OSCs) are promising candidates for next‐generation photovoltaic technologies, with their power conversion efficiencies (PCEs) reaching 19%. However, the typically used spin‐coating method, toxic halogenated processing solvents, and the conventional bulk‐heterojunction (BHJ), which causes excessive charge recombination, hamper the commercialization and further efficiency promotion of OSCs. Here, a simple but effective dual‐slot‐die sequential processing (DSDS) strategy is proposed to address the above issues by achieving a continuous solution supply, avoiding the solubility limit of the nonhalogen solvents, and creating a graded‐BHJ morphology. As a result, an excellent PCE of 17.07% is obtained with the device processed with o‐xylene in an open‐air environment with no post‐treatment required, while a PCE of over 14% is preserved in a wide range of active‐layer thickness. The unique film‐formation mechanism is further identified during the DSDS processing, which suggests the formation of the graded‐BHJ morphology by the mutual diffusion between the donor and acceptor and the subsequent progressive aggregation. The graded‐BHJ structure leads to improved charge transport, inhibited charge recombination, and thus an excellent PCE. Therefore, the newly developed DSDS approach can effectively contribute to the realm of high‐efficiency and eco‐friendly OSCs, which can also possibly be generalized to other organic photoelectric devices.

Molecule engineering has been demonstrated as a valid strategy to adjust the active layer morphology in all‐small‐molecule organic solar cells (ASM‐OSCs). In this work, two non‐fullerene acceptors (NFAs), FO‐2Cl and FO‐EH‐2Cl, with different alkyl side chains are reported and applied in ASC‐OSCs. Compared with FO‐2Cl, FO‐EH‐2Cl is designed by replacing the octyl alkyl chains with branched iso‐octyl alkyl chains, leading to an enhanced molecular packing, crystallinity, and redshifted absorption. With a small molecule BSFTR as donor, the device of BSFTR:FO‐EH‐2Cl obtains a better morphology and achieves a higher power conversion efficiency (PCE) of 15.78% with a notable fill factor (FF) of 80.44% than that of the FO‐2Cl‐based device with a PCE of 15.27% and FF of 78.41%. To the authors’ knowledge, the FF of 80.44% is the highest value in ASM‐OSCs. These results demonstrate a good example of fine‐tuning the molecular structure to achieve suitable active layer morphology with promising performance for ASM‐OSCs, which can provide valuable insight into material design for high‐efficiency ASM‐OSCs.