Near-infrared (NIR) light has shown great potential for military and civilian applications owing to its advantages in the composition of sunlight, invisibility to human eyes, deeper penetration into biological tissues, and low optical loss in optical fibers. Therefore, organic optoelectronic materials that can absorb or emit NIR light have aroused great scientific interest in basic science and practical applications. Based on these NIR organic optoelectronic materials, NIR optoelectronic devices have been greatly improved in performance and application. In this review, the representative NIR organic optoelectronic materials used in organic solar cells, organic photodetectors, organic light-emitting diodes, organic lasers, and organic optical waveguide devices are briefly introduced, and the potential applications of each kind of device are briefly summarized. Finally, we summarize and take up the development of NIR organic optoelectronic materials and devices.

The stability of organic solar cells (OSCs) remains a major concern for their ultimate industrialization due to the photo, oxygen, and water susceptibility of organic photoactive materials. Usually, antioxidant additives are blended as radical scavengers into the active layer. However, it will induce the intrinsic morphology instability and adversely affect the efficiency and long-term stability. Herein, the antioxidant dibutylhydroxytoluene (BHT) group has been covalently linked onto the side chain of benzothiadiazole (BT) unit, and a series of ternary copolymers D18-Cl-BTBHTx (x = 0, 0.05, 0.1, 0.2) with varied ratio of BHT-containing side chains have been synthesized. It was found that the introduction of BHT side chains would have a negligible effect on the photophysical properties and electronic levels, and the D18-Cl-BTBHT0.05: Y6-based OSC achieved the highest power conversion efficiency (PCE) of 17.6%, which is higher than those based active layer blended with BHT additives. More importantly, the unencapsulated device based on D18-Cl-BTBHTx (x = 0.05, 0.1, 0.2) retained approximately 50% of the initial PCE over 30 hours operation under ambient conditions, significantly outperforming the control device based on D18-Cl (90% degradation in PCE after 30 h). This work provides a new structural design strategy of copolymers for OSCs with simultaneously improved efficiency and stability.

With the emergence of new materials for high-efficiency organic solar cells (OSCs), understanding and finetuning the interface energetics become increasingly important. Precise determination of the so-called pinning energies, one of the critical characteristics of the material to predict the energy level alignment (ELA) at either electrode/organic or organic/organic interfaces, are urgently needed for the new materials. Here, pinning energies of a wide variety of newly developed donors and non-fullerene acceptors (NFAs) are measured through ultraviolet photoelectron spectroscopy. The positive pinning energies of the studied donors and the negative pinning energies of NFAs are in the same energy range of 4.3?4.6 eV, which follows the design rules developed for fullerene-based OSCs. The ELA for metal/organic and inorganic/organic interfaces follows the predicted behavior for all of the materials studied. For organic–organic heterojunctions where both the donor and the NFA feature strong intramolecular charge transfer, the pinning energies often underestimate the experimentally obtained interface vacuum level shift, which has consequences for OSC device performance.With the emergence of new materials for high-efficiency organic solar cells (OSCs), understanding and finetuning the interface energetics become increasingly important. Precise determination of the so-called pinning energies, one of the critical characteristics of the material to predict the energy level alignment (ELA) at either electrode/organic or organic/organic interfaces, are urgently needed for the new materials. Here, pinning energies of a wide variety of newly developed donors and non-fullerene acceptors (NFAs) are measured through ultraviolet photoelectron spectroscopy. The positive pinning energies of the studied donors and the negative pinning energies of NFAs are in the same energy range of 4.3?4.6 eV, which follows the design rules developed for fullerene-based OSCs. The ELA for metal/organic and inorganic/organic interfaces follows the predicted behavior for all of the materials studied. For organic–organic heterojunctions where both the donor and the NFA feature strong intramolecular charge transfer, the pinning energies often underestimate the experimentally obtained interface vacuum level shift, which has consequences for OSC device performance.