In-situ photoisomerization of azobenzene to inhibit ion-migration for stable high-efficiency perovskite solar cells

Ion migration is a notorious problem in perovskite solar cells(PSCs)that severely mutilates device performance.Herein,a strategy to inhibit ion migration in situ is developed by using photoisomerization of azobenzene(AZO)to immobilize cations in the lattice.During the nucleation process,the photoisomerized cis-AZO reacts with FA^(+),MA^(+)and Pb2+cations in the perovskite precursor by synergistic cation-πinteraction and Lewis base coordination,leading to heterogeneous nucleation to produce uniform perovskite film.Meanwhile,it accelerates conversion of intermediate yellowδ-phase to desired black aphase of FAPb I3for improved crystallinity with well-passivated grain surface.Consequently,defect density is effectively reduced for the perovskite film to demonstrate suppressed carrier recombination and enhanced carrier extraction.Subsequently,the solar cell efficiency is elevated from 21.29%to 23.58%with negligible J-V hysteresis.Long-term stability is also improved,with the bare device without any encapsulation retaining 84%of its initial efficiency after aging 744 hours in ambient.

High-efficiency organic solar cells processed from a halogen-free solvent system

The use of non-halogenated solvents for the green manufacture of high-efficiency organic solar cells(OSCs)is important for their future application.However,the power conversion efficiency(PCE)of the non-halogenated solvent processed OSCs is generally lower than their halogenated counterpart due to the poor film microstructure caused by the solubility issue.Herein,we propose a halogen-free solvent system to optimize film microstructure of the photovoltaic blend based on the polymer donor D18and small-molecule acceptor(SMA)L8-BO towards high-efficiency OSCs.The solvent system is consisted of a main solvent carbon disulfide and an additive paraxylene,where the former ensures the good solution-processability and promotes the solution aggregation of L8-BO,and the latter can finely control the phase-separation process by selectively dissolving the SMA.This solvent combination robustly produces a high-quality active layer,i.e.,the bicontinuous networks of donor and acceptor with nano-sized phase-separation and strongπ-πstacking.With the effective charge generation,transport and collection,the resulting device from the non-halogenated solvent system shows a high PCE of 17.50%,which is comparable to that of the device prepared from the halogenated solvent chloroform(ca.17.11%).This article proposes a new strategy for the green fabrication of high-efficiency OSCs to accelerate their industrialization.

Mobile Internet Big Data Platform in China Unicom

China Unicorn, the largest WCDMA 3G operator in China, meets the requirements of the historical Mobile Internet Explosion, or the surging of Mobile Internet Traffic from mobile terminals. According to the internal statistics of China Unicom, mobile user traffic has increased rapidly with a Compound Annual Growth Rate （CAGR） of 135%. Currently China Unicorn monthly stores more than 2 trillion records, data volume is over 525 TB, and the highest data volume has reached a peak of 5 PB. Since October 2009, China Unicom has been developing a home-brewed big data storage and analysis platform based on the open source Hadoop Distributed File System （HDFS） as it has a long-term strategy to make full use of this Big Data. All Mobile Internet Traffic is well served using this big data platform. Currently, the writing speed has reached 1 390 000 records per second, and the record retrieval time in the table that contains trillions of records is less than 100 ms. To take advantage of this opportunity to be a Big Data Operator, China Unicom has developed new functions and has multiple innovations to solve space and time constraint challenges presented in data processing. In this paper, we will introduce our big data platform in detail. Based on this big data platform, China Unicom is building an industry ecosystem based on Mobile Internet Big Data, and considers that a telecom operator centric ecosystem can be formed that is critical to reach prosperity in the modern communications business.