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Design of host-guest structure has been an important direction in the development of organic long-persistent luminescence (LPL) materials, which have challenged traditional inorganic materials in some applications, such as anti-counterfeiting and bioimaging. The charge separation of donor-acceptor between host and guest is an effective way to induce LPL emission. Here, three crystalline materials were prepared by a convenient host-guest doping method at room temperature under ambient surrounding, i.e. in the presence of oxygen. Two kinds of crystals with long-lived charge separated states exhibited visible LPL emission with over 8 s and 6 s of duration. The persistent room-temperature phosphorescence effect caused by different generation efficiency of charge separated states was the main reason for the difference of LPL duration time. The crystal without charge separation had no LPL phenomenon because it was not a donor-acceptor system. This work indicates that the generation of charge separated states and their generation efficiency are the two key factors affecting the LPL properties and provides a new understanding for the design of organic LPL materials. [Display omitted] • Three crystalline materials with D-A architecture are prepared by a convenient doping method. • Charge-separation can be directly related to the long-persistent luminescence (LPL). • Generation efficiency of charge-separation can affect the LPL duration time. [ABSTRACT FROM AUTHOR]

Traditional long‐persistent luminescence (LPL) materials, which are based on inorganic systems containing rare elements and with preparation temperatures of at least 1000 °C, exhibit afterglow times of more than 10 h and can be tuned for different applications. However, the development of this field is hindered due to the large thermal energy consumption and the need for nonrenewable resources. Thus, the development of a "green" design and preparation of LPL materials is of some importance. A doped‐crystalline material based on two metal‐free organic small molecules is easily prepared through ultrasonic crystallization at room temperature. It has a high‐quality, single‐crystalline structure, and visible LPL performance with a duration of more than 6 s upon low‐energy photoexcitation. A green, flexible, and convenient screen‐printing technology for controllable pattern anticounterfeiting is then developed from this purely organic material, which improves the prospects for commercial utilization in the future. [ABSTRACT FROM AUTHOR]