TikTok is the international twin of China’s mobile short video app, Douyin, and one of the fastest growing short video platforms in the world. Owned by Chinese tech giant, ByteDance, TikTok and Douyin share many similarities in terms of appearance, functionality, and platform affordances; however, they exist in radically different markets and are governed by radically different forces. Unlike other popular mobile media platforms in China and internationally, TikTok and Douyin are neither part of the big three tech giants in China nor the big five in the US. This provides an interesting case study to investigate how an emerging internet company adapts its products to better fit divergent expectations, cultures, and policy frameworks in China and abroad. Using the app walkthrough method informed by platformization of culture production theory, this study highlights the similarities and distinctions between these two platforms. We argue the co-evolution of Douyin and TikTok is a new paradigm of global platform expansion that differs from strategies of regionalization adopted by previous major social media platforms. We contribute to platformization theory by developing the concept of parallel platformization to explain ByteDance’s strategies for surviving in two opposing platform ecosystems in China and abroad.

The performance of perovskite solar cells (PSCs) strongly depends on the electron transport layer (ETL), perovskite absorber, hole transport layer (HTL), and their interfaces. Herein, the first approach to utilize ultrathin 2D titanium‐carbide MXenes (Ti3C2Tx quantum dots, TQD) by engineering the perovskite/TiO2 ETL interface and perovskite absorber and introducing Cu1.8S nanocrystals to perfect the Spiro‐OMeTAD HTL is represented. A significant hysteresis‐free power conversion efficiency improvement from 18.31% to 21.64% of PSCs is achieved after modifications with the enhanced short‐circuit current density, open‐circuit voltages, and fill factor. Various advanced characterizations, including femtosecond transient absorption spectroscopy, electrochemical impedance spectroscopy, and ultraviolet photoelectron spectroscopy, elucidate that the TQD/Cu1.8S significantly contribute to the improved crystalline quality of the perovskite film with its large grain size and improved electron/holes extraction efficiencies at perovskite/ETL and perovskite/HTL interfaces. Furthermore, the long‐time ambient and light stability of PSCs are largely boosted through the TQD and/or Cu1.8S nanocrystals doping, originating from the better crystallization of perovskite, suppressing the film aggregation and crystallization of HTL, and inhibiting the ultraviolet‐induced photocatalysis of the ETL. The findings highlight the TQD and Cu1.8S can act as a superfast electrons and holes tunnel for the optoelectronic devices.

Hydrochromic materials have attracted widespread attention in the fields of anti-counterfeiting because of their ability of the reversible light absorption and/or emission properties in response to water. Here, for the first it is demonstrated that the ternary copper halides Cs 3 Cu 2 I 5 nanocrystals (NCs) possess excellent hydrochromic properties. The prepared Cs 3 Cu 2 I 5 NCs films can dynamically extract and insert CsI by exposing/removing water to realize the reversible conversion between blue-emissive Cs 3 Cu 2 I 5 and yellow-emissive CsCu 2 I 3 . Interestingly, polymethyl methacrylate (PMMA) coated Cs 3 Cu 2 I 5 can effectively avoid the extraction of CsI and maintain long-term stability in the water. Further, the hydrochromic Cs 3 Cu 2 I 5 and water-resistant Cs 3 Cu 2 I 5 @PMMA are used as the inks to synergistically act on anti-counterfeiting information to achieve multiple encryption effects, which can clearly identify and authenticate the effective information after moisture decryption. Importantly, the pattern can be re-encrypted to the invalid pattern after water evaporation. In addition, the anti-counterfeiting pattern has excellent stability during repeated encryption/decryption conversion cycles, which can not only balance the accessibility of anti-counterfeiting information but also effectively improve the security of information. This new discovery may not only deepen the understanding of Cs 3 Cu 2 I 5 but also provide new options for the design of hydrochromic materials for anti-counterfeiting information.