Single layered organic solar cells (OSCs) using non-fullerene acceptors have This article is protected by copyright. All rights reserved. 35A power conversion efficiency of 16.88% (certified as 16.4%) is achieved based on PM6:Y6 by morphology optimization, which is the top efficient for organic solar cells. Through the study of single structure and film morphology, a well ordered 2D crystal was found, which helps to enhance ultrafast hole and electron transfer, thus improving performance.

The chemical structure of donors and acceptors limit the power conversion efficiencies achievable with active layers of binary donor-acceptor mixtures. Here, using quaternary blends, double cascading energy level alignment in bulk heterojunction organic photovoltaic active layers are realized, enabling efficient carrier splitting and transport. Numerous avenues to optimize light absorption, carrier transport, and charge-transfer state energy levels are opened by the chemical constitution of the components. Record-breaking PCEs of 18.07% are achieved where, by electronic structure and morphology optimization, simultaneous improvements of the open-circuit voltage, short-circuit current and fill factor occur. The donor and acceptor chemical structures afford control over electronic structure and charge-transfer state energy levels, enabling manipulation of hole-transfer rates, carrier transport, and non-radiative recombination losses.

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.

Non-fullerene fused-ring electron acceptors boost the power conversion efficiency of organic solar cells, but they suffer from high synthetic cost and low yield. Here, we show a series of low-cost noncovalently fused-ring electron acceptors, which consist of a ladder-like core locked by noncovalent sulfur–oxygen interactions and flanked by two dicyanoindanone electron-withdrawing groups. Compared with that of similar but unfused acceptor, the presence of ladder-like structure markedly broadens the absorption to the near-infrared region. In addition, the use of intramolecular noncovalent interactions avoids the tedious synthesis of covalently fused-ring structures and markedly lowers the synthetic cost. The optimized solar cells displayed an outstanding efficiency of 13.24%. More importantly, solar cells based on these acceptors demonstrate very low non-radiative energy losses. This research demonstrates that low-cost noncovalently fused-ring electron acceptors are promising to achieve high-efficiency organic solar cells.

Spectroscopic photodetection is a powerful tool in disciplines such as medical diagnosis, industrial process monitoring, or agriculture. However, its application in novel fields, including wearable and bio-integrated electronics is hampered by the use of bulky dispersive optics. Here, we employ solution-processed organic donor-acceptor blends in a resonant optical cavity device architecture for wavelength-tunable photodetection. While conventional photodetectors respond to above-gap excitation, the cavity device exploits weak subgap absorption of intermolecular charge-transfer states of the intercalating Poly[2,5-bis(3-tetradecylthiophen-2-yl)thieno[3,2-b]thiophene] (PBTTT):[6,6]-Phenyl-C61-butyric acid methyl ester (PCBM) bimolecular crystal. This enables a highly wavelength selective, nearinfrared photoresponse with a spectral resolution down to 14 nm, as well as dark currents and detectivities comparable with commercial inorganic photodetectors. A miniaturized spectrophotometer, comprising an array of narrowband photo-detectors is fabricated using blade-coated PBTTT:PCBM thin films with a thickness gradient. As application example, we demonstrate water transmittance spectral measured by this device.