Although perovskite solar cells (PSCs) have emerged as a promising alternative to widely used fossil fuels, the involved high‐temperature preparation of metal oxides as a charge transport layer in most state‐of‐the‐art PSCs has been becoming a big stumbling block for future low‐temperature and large‐scale R2R manufacturing process. Such an issue strongly encourages scientists to find new type of materials to replace metal oxides. Except for expensive PC61BM with unmanageable morphology and electrical properties, the past investigation on the development of low‐temperature‐processed and highly efficient electron transport layers (ETLs) has met some mixed success. In order to further enhance the performance of all‐solution‐processed PSCs, we propose a novel n‐type sulfur‐containing small molecule hexaazatrinaphtho[2,3‐c][1,2,5]thiadiazole (HATNT) with high electron mobility up to 1.73 × 10−2 cm2 V−1 s−1 as an ETL in planar heterojunction PSCs. A high power conversion efficiency of 18.1% is achieved, which is fully comparable with the efficiency from the control device fabricated with PC61BM as ETL. This superior performance mainly attributes from more effective suppression of charge recombination at the perovskite/HATNT interface than that between the perovskite and PC61 BM. Moreover, high electron mobility and strong interfacial interaction via SI or SPb bonding should be also positive factors. Significantly, our results undoubtedly enable new guidelines in exploring n‐type organic small molecules for high‐performance PSCs.

In fact, the reason that these hybrid perovskites receive so much attention is their excellent optoelectronic properties, such as high carrier mobility, long carrierdiffusion length (>100 µm), small exciton binding energy, and strong light-absorption ability in the UV-vis range. [12][13][14][15][16][17][18][19][20][21][22][23][24][25] The rich optoelectronic properties in their bulky state make scientists believe that reducing their sizes to the nanoscale should bring further unprecedented physical phenomena. Perovskite nanocrystals are tiny particles with dimensional variation from several to hundreds of nanometers, and their corresponding properties are highly correlated to the sizes, shapes, and crystallographic structures of the as-prepared nanocrystals. [26] The first reported synthesis of hybrid perovskite nanocrystals emerged in 2014, where Julia et al. demonstrated how to fabricate 6 nm sized organic-inorganic hybrid perovskite nanocrystals through a simple and fast method based on the use of an ammonium bromide with a medium-length alkyl chain. [27] In 2015, Kovalenko and co-workers firstly realized the synthesis of all-inorganic perovskite nanocrystals. [28] Since then, different perovskite nanocrystals have been successfully prepared in succession. [29,30] As emerging materials, perovskite nanocrystals have received great attention in a very short time due to their remarkable characteristics including high fluorescence quantum efficiency, narrow emission band width, and decent stability. [31,32] Great efforts have been devoted to exploring new synthetic routes, basic material properties, and photophysical behavior. According to the morphologies of the as-obtained perovskite nanocrystals, these nanomaterials can be generally divided into amorphous nanoparticles, nanocubes, nanoplatelets, and nanowires. Because of their diverse morphologies and tunable optical properties, different optoelectronic applications based on perovskite nanocrystals have sprung up. [32] Except for well-developed perovskite photovoltaics, red/green/blue perovskite-based light-emitting diodes have been reported. [32][33][34] Furthermore, amplified spontaneous emission and lasing based on these nanocrystals have also been realized. [35][36][37] Here, we will only focus on the recent progress in perovskite nanocrystals including synthetic methods and their applications beyond solar cells, since numerous scientific articles related to perovskite solar cells have been carefully summarized. Specifically, different synthetic routes to prepare perovskite nanocrystals will be introduced, [38][39][40][41][42][43] followed by their various applications, including perovskite light-emitting diodes, amplified spontaneous emission and lasing, photodetectors, resistance random access memory devices, and piezoelectric nanogenerators.The recent progress in perovskite nanocrystals, including synthetic methods and their applications beyond solar cells, is discussed. Specifically, different synthetic routes to prepare various perovskite nanocrystals ...

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The introduction of CuSCN as the hole injection material significantly improved the turn-on voltage of quantum dot-based LEDs.