However, the impressive high PCE was obtained from small area cell (<1 cm 2) using non-up-scalable spin coating method in nitrogen. [1-3] To make commercially viable PSC, the development of low cost and large area fabrication process in ambient air is imperative. Many processes are available in industry for largescale area coating such as dip coating, blade coating, and slot-die coating, etc. Among them, the slot-die coating is preferable because the precision control of coating thickness and solution usage (i.e., minimum wastage of material). [4-7] The slot-die coating is also suitable to be adopted for continuously process which can reduce the cost of manufacturing even further. High performance PSC has been fabricated by scalable process such as blade coating, slot-die coating and spray coating. [8-14] However, most of studies concentrated on the perovskite layer processing in controlled environment. Only limited reports are on the scalable process operated in ambient air. [15-18] The commonly used architecture of p-in PSCs contains four layers deposited by solution process, and those four layers include hole transport layer (HTL), light absorption perovskite layer, electron transport layer (ETL) and work function modifier layer (WFL). First, all the solvents used in the processing of each layer should be nontoxic for the scalable process. [19-21] Then the balance among suitable chemical composition of each layer, solvent type, film morphology control, compatibility between layers, the stability of each layers to have a workable ambient air processing system is quite challenge in terms of science and engineering. The film morphology and compatibility of each layer of PSCs are controlled by the chemical compositions of each layer and processing condition. For the perovskite layer, the film morphology is determined by the kinetic rate of solvent evaporation and crystallization. [22-23] For spin coating, most of the solvents are removed rapidly by the coater rotation and the anti-solvent dripping. [24] However, the rate of the solvent evaporation of slot-die coating is lower than that of spin coating. [17,25-26] The strategies such as anti-solvent bath, gas quenching and pre-heat substrate method are adopted to increase the rate of solvent evaporation. [11,27-31] Although the high PCE devices can be achieved, the results are only performed on small-area substrate. If the Currently, high-efficiency perovskite solar cells are mainly fabricated by the spin-coating process, which limits the possibility of commercial mass-production of perovskite solar cells. In this work, the slot-die coating process is combined with near-infrared irradiation heating to quickly manufacture perovskite solar cells in air. The composition of the perovskite precursor solution is tuned by adding n-butanol, with its low boiling point and low surface tension, to increase the near-infrared energy absorption, facilitate the evaporation of the solvent system and film formation, and accelerate the crystallization of perovskite. High-quality uni...

No abstract

The composite electron transporting layer (ETL) of metal oxide with [6,6]-phenyl-C 61 -butyric acid methyl ester (PCBM) prevents perovskite from metal electrode erosion and increases p−i−n perovskite solar cell (PVSC) stability. Although the oxide exhibits protective function, an additional work function modifier is still needed for good device performance. Usually, complicated multistep synthesis is employed to have a highly crystalline film that increases manufacturing cost and inhibits scalability. We report a facile synthesis of a novel organic-molecule-capped metal oxide nanoparticle film for the composite ETL. The nanoparticle film not only has a dual function of electron transport and protection but also exhibits work function tunability. Solvothermal-prepared SnO 2 nanoparticles are capped with tetrabutylammonium hydroxide (TBAOH) through ligand exchange. The resulting TBAOH−SnO 2 nanoparticles disperse well in ethanol and form a uniform film on PCBM. The power conversion efficiency of the device dramatically increases from 14.91 to 18.77% using this layer because of reduced charge accumulation and aligned band structure. The PVSC thermal stability is significantly enhanced by adopting this layer, which prevents migration of I − and Ag. The ligand exchange method extends to other metal oxides, such as TiO 2 , ITO, and CeO 2 , demonstrating its broad applicability. These results provide a cornerstone for large-scale manufacture of high-performance and stable PVSCs.

Two issues need to be resolved when fabricating p-i-n semitransparent perovskite solar cells (ST-PVSCs) for four-terminal (4 T) perovskite/silicon tandem solar cells: 1) damage to the underlying absorber (MAPbI 3 ), electron transporting layer ([6,6]-phenyl-C 61 -butyric acid methyl ester, PCBM), and work function (WF) modifier (polyethylenimine, PEI), resulting from the harsh sputtering conditions for the transparent electrodes (TEs) and 2) low average nearinfrared transmittance (ANT) of TEs. Herein, a unique SnO 2 layer to protect the MAPbI 3 and PCBM layers is developed and functions as a WF modifier for a new TE (cerium-doped indium oxide, ICO), which exhibits an excellent ANT of 86.7% in the range of 800À1200 nm. Moreover, a MAPbI 3 -based p-i-n ST-PVSC is prepared, achieving an excellent power conversion efficiency (PCE) of 17.23%. When it is placed over the Si solar cell, a 4 T tandem solar cell with a PCE of 26.14% is obtained.

No abstract