The unavailable long-life, low-energy, super high-capacity, and renewable and sustainable optical data storage remains a severe challenge to be conquered, which promotes researchers to spare no efforts in designing and fabricating novel systems using more remarkable optical storage materials [1,2,3,4,5]. So far, the total amount of annual data produced globally has increased very fast, which has doubled every two years since 2000 [6]. The traditional technologies including magnetic storage and electrical storage have been improved to deal with the explosive growth of mass information; however, the commercialized products are mainly developed via the two technologies with limited capacity, and the strategies for expanding capacity have reached a bottleneck that is extremely hard to be broken [7,8]. Moreover, the serious drawbacks such as strict storage conditions, the high energy consumption of equipment, and low-security level have restricted the further improvement of magnetic storage and electrical storage, which are difficult to adapt to the booming information era [9,10]. Optical storage materials have been one of the most common recording mediums since the beginning of the 21st century, accompanied by the rapid development of laser technology. Optical storage is the technology that is based on the interaction between laser and recording medium, and the investigation on breaking the diffraction limit for conquering the challenge of present data storage has attracted extensive attention in information technology industry [11]. Compared to the traditional means, optical storage technology shows more possibility for satisfying the requirements of data storage equipped with the properties including large capacity, high safety, intense stability, reasonable price, and low energy consumption [12]. In the past decade, researchers have devoted themselves to exploring new functional materials to be applied in recording media. Meanwhile, the representative recording media such as rare-earth doped upconversion nanoparticles (UCNPs) [13,14,15,16,17], graphene derivatives (GDs) [18,19,20,21], and diarylethene derivatives (DTDs) [22,23,24,25,26] are the most potential materials to be further investigated, which are promising to facilitate the development of optical storage technology and exploit valuable strategies for practical applications and industrialized projects [27,28,29,30,31,32].

The low-energy near-infrared light can be transferred to high-energy UV light or visible light by using the functionalized UCNPs, which is developed for the applications in photolithography, photothermal therapy, photoswitch, and optical storage [33,34]. The UCNPs possess distinct fluorescence properties, which can be incorporated into luminescent materials such as quantum dots, organic dyes, and aggregation-induced emission luminogens (AIEgens) to fabricate novel recording materials equipped with large memory capacities. In comparison with common organic fluorescence chromophores, the UCNPs possess wider energy levels to further reduce transition rates, enabling the low power-assisted stimulated emission depletion (STED) effects to play a crucial role in optical storage [35].

So far, the standardization production of graphene has received remarkable achievements, and the representative industrial process derived from chemical vapor deposition and epitaxial growth has gained rapid development [36,37,38]. In order to overcome the challenge of production modes, the architecture of graphene-based materials like graphene nanobelt and graphene quantum dots has been widely reported to be applied in the construction of field effect transistors, bioimaging, and optical writing [39]. Thus, the significance of designing new graphene nanostructures is in urgent need to cooperate with super-resolution microscopy technology, for the extensive imaging of GD substrates. The majority of receptor systems only can be quenched in a narrowed spectral range; however, the GDs are equipped with the feature of broadband absorption to exhibit energy transfer in the whole visible spectrum, possessing great potential to be introduced in macromolecular systems to prepare composite materials for the application in optical storage [40].

Moreover, on the basis of the established UCNPs, the inorganic–organic hybrid materials are well constructed, combining the merits of UCNPs and organic stimuli-responsive molecules for proposing a new approach to advanced optical storage [41]. The DTDs are the most used organic molecules for optical writing because of their photo-isomerization properties. As the typical photoresponsive molecules, DTDs show vital values in the practical application of the reversible memory assisted by the photoswitched “writing–reading–erasing” [42]. Generally, DTDs can finish the rapid transformation between open and close conformations irradiated by the UV light and visible light, respectively. More importantly, DTDs have favorable physicochemical properties, including strong thermal stability, moderate fatigue resistance, a quick responsiveness and reaction rate, a high-conversion ratio of open/close isomers, sufficient quantum yield, and an obvious difference of absorption wavelength between the open/close isomers. The DTD-based composites play a crucial part in optical storage owing to their significant changes of absorption spectra, dielectric constants, and geometrical configuration, and have tremendous commercial values for optical storage revolution in the future [43,44,45].

The optical storage materials are one of the most promising recording media in the digital age [46]. Researchers have been sparing no efforts on the in-depth exploration of the three functional memory materials for pursuing a larger storage density [47,48,49,50,51]. According to the strategies of increasing the number of layers, enhancing the recording dimensions of recording media, and narrowing the diffraction limit, we envision that the ultrahigh storage density of the TB level, even PB level, will eventually be approached in a single disc [6,52].

The technology of high-density optical writing is of great significance in data storage. Additionally, the optical writing technology at nanoscale level based on the far-field super-resolution method provides a unique approach for dealing with memory devices with a large capacity. However, the current nanoscaled optical writing measures generally rely on the mechanism of photo-initiation and photo-inhibition, which seriously restricts their further development due to the disadvantages of the high intensity of laser, large consumption of energy, and short life of devices [53]. Notably, the UCNP-based systems have broad excitation levels to decrease transition rates. Meanwhile, according to the far-field super-resolution technology, the electron transition in UCNP-based systems can be selectively modulated to activate the energy transfer-derived low-power radiation for breaking through the diffraction limit in optical writing. In this section, the diverse UCNP materials used for optical writing and optical storage with particular functions are discussed in detail (Table 1).