Perovskite solar cells (PSCs) have developed rapidly over the past few years, and the power conversion efficiency of PSCs has exceeded 20%. Such high performance can be attributed to the unique properties of perovskite materials, such as high absorption over the visible range and long diffusion length. Due to the different diffusion lengths of holes and electrons, electron transporting materials (ETMs) used in PSCs play a critical role in PSCs performance. As an alternative to TiO ETM, ZnO materials have similar physical properties to TiO but with much higher electron mobility. In addition, there are many simple and facile methods to fabricate ZnO nanomaterials with low cost and energy consumption. This review focuses on recent developments in the use of ZnO ETM for PSCs. The fabrication methods of ZnO materials are briefly introduced. The influence of different ZnO ETMs on performance of PSCs is then reviewed. The limitations of ZnO ETM-based PSCs and some solutions to these challenges are also discussed. The review provides a systematic and comprehensive understanding of the influence of different ZnO ETMs on PSCs performance and potentially motivates further development of PSCs by extending the knowledge of ZnO-based PSCs to TiO -based PSCs.

optical properties. However, such materials are either expensive or require vacuum equipment, e.g., metal-organic chemical vapor deposition, to fabricate, [7][8][9] which places a restriction on a wide deployment. In recent years, organometal trihalide perovskites (OTPs) (with a structure of ABX 3 , where A is an organic cation CH 3 NH 3 + (MA), B is Pb 2+ , X is a halide anion or mixed halide) have drawn great attention and been a very promising candidate for opto-electronic applications due to low cost and high throughput solution process. Since the discovery of perovskitebased solar cells (PSCs) by Miyasaka and co-workers [10] power conversion efficiencies have exceeded 22% in less than seven years, [11] thanks to the outstanding physics properties, including the low exciton binding energy, strong light absorption, long carrier lifetime, large carrier diffusion coefficient, and low charge recombination rate. [12][13][14][15][16] These features also make the emerging perovskite materials a promising alternative to conventional semiconductors used in PDs. Indeed, solution-processed OTPs have yielded PDs with excellent device performance. [16][17][18][19][20][21][22][23][24] For instance, both polycrystalline films and single crystals of OTPs have been successfully used to fabricate the narrowband and broadband photodetectors. [25][26][27] As one of the earliest discovered and extensively researched perovskite materials, MAPbI 3 has been regarded as one of the most potential materials for PDs due to its broadband absorption and superb light sensitivity. Dong et al. reported a MAPbI 3 -based photodetector with excellent photoconductive properties. [20] Su et al. reported a self-powered photodetector based on MAPbI 3, which exhibited excellent responsivity and rapid response time for wavelength ranging from ultraviolet to visible light. [28] Chen et al. fabricated a flexible UV-vis-NIR photodetector based on MAPbI 3 with excellent mechanical flexibility and durability. [18] However, some issues about this material still exist. MAPbI 3 tends to degrade and dissociate into MAI and PbI 2 in air. [29][30][31] Recent work on FAPbX 3 (FA: CH 3 (NH 2 ) 2 + , X = I, Br, Cl) PSCs demonstrates better thermal durability than methylammonium perovskites. [31,32] However, FAPbI 3 has two different phases at room temperature: α-phase (desired perovskite phase) and δ-phase (photo-inactive phase). Also, the α-phase perovskite of FAPbI 3 , which is sensitive to solvents and moisture, would turn into the undesired δ-phase in an air atmosphere. [33] Photodetectors, which can convert light signals into electrical signals, are important opto-electronic devices in imaging, optical communication, biomedical/biological sensing, and so on. Here a solution-processed photodetector based on the triple cation perovskite is demonstrated. The perovskite photodetectors show a high detectivity, high speed, as well as excellent environmental stability. Operating at a low voltage bias of 2 V, the photodetectors exhibit a large on/off ratio of 10 5 , ...

Impurity-mediated near-infrared (NIR) photoresponse in silicon is of great interest for photovoltaics and photodetectors. In this paper, we have fabricated a series of n+/p photodetectors with hyperdoped silicon prepared by ion-implantation and femtosecond pulsed laser. These devices showed a remarkable enhancement on absorption and photoresponse at NIR wavelengths. The device fabricated with implantation dose of 1014 ions/cm2 has exhibited the best performance. The proposed method offers an approach to fabricate low-cost broadband silicon-based photodetectors.

Formamidinium iodide (FAI) based perovskite solar cells (PSCs) have now been established as effective PSCs than methylammonium lead iodide perovskite for several years due to their optimal bandgap and high thermal stability.However, the FAI-based PSCs have humidity issues, due to which mixed cation perovskites are getting popular. MAI-based PSCs have better stability against high humidity but low thermal stabilities. Herein, we prepared highly crystallized, efficient, and large-grain size perovskite films via FAI postdripping process. In addition, the most promising structures FAI mixed MAPbI 3 were explored as stable and effective active layers. The post-dripping of FAI solution just after the MAPbI 3 deposition provides a robust longdistance diffusion, long carrier life, and enhanced grain sizes when compared to MAPbI 3 PSCs. Based on the facile way of mixed cation perovskite preparation by post-dripping, the power conversion efficiency (PCE) has risen from 15.24% to 17.52% in comparison with the pristine devices. This results in the best quality and large grain perovskite films which enhanced the PSCs' performance by reducing defect density and regulating the crystallization rate.

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