Regulation of the crystallization of perovskite films and avoiding the oxidation of Sn2+ during the deposition process are very important for achieving Sn/Pb binary perovskite solar cells (PVSCs) with high power conversion efficiency (PCE) and producibility. In this work, a high‐quality HC(NH2)2Pb0.7Sn0.3I3 (FAPb0.7Sn0.3I3) film deposited from the two‐step solution process by introducing methylammonium thiocyanate (MASCN) as a bifunctional additive into the precursor solution containing PbI2 and SnI2 is reported. MASCN can not only tune the morphology of the perovskite film but also stabilize the precursor solution via retarding the oxidation of Sn2+ through a strong coordination between SCN− and Sn2+. The Sn/Pb binary inverted PVSCs based on FAPb0.7Sn0.3I3 present a high fill factor of 0.79 and the best PCE of 16.26% in the case of 0.25 MASCN addition. The device fabrication producibility is also greatly improved due to the stabilized precursor solution with the aid of MASCN. The PCE of the device is almost independent of the storage time of the precursor solution within 124 d in the N2‐filled glove box. These results indicate that the precursor engineering with multifunctionality additive is an effective approach toward highly efficient and producible PVSCs for future commercialization.

cell (PVSCs) with good reproducibility, beneficial for improving success rate of products. Besides of the uniformity of perovskite layer, the fabrication of highly efficient PVSC with thick perovskite layer and good thickness tolerance is also urgent for future commercializatio n. [1b,2c,e,5] In the past three years, efforts on fabricating high-performance PVSCs with thick active layer were tried by both thermal evaporation and solution methods. [1b,2c,e,5a,6] The researches on the PVSCs based on perovskite film fabricated by thermal evaporation method revealed that there is an optimized film thickness ≈300 nm. Further increase the thickness of the perovskite film leads to the deterioration of open-circuit voltage (V oc ) and fill factor (FF) and the decline of PCE of the device. [6a,b,7] Though Bolink and co-workers [6a] reduce the effect of the unbalanced charge extraction for 900 nm thick PVSCs by increasing the conductivity of the hole transport layer (HTL), and improve the efficiency from 7.2% to 12.0%, which is still lower than the 285 nm thick one (12.7%). It is believed that the reduction of V oc and FF along with the increasing film thickness can be attributed to the roughening of the surface of the perovskite film and the perovskite/carrier transport layer interface as well, which brings more serious charge recombination. [6b,7] Similar phenomenon was also observed in the perovskite film prepared by spin-coating method. Gong and co-workers [6c] found that the PCE first increased with the increasing thickness of the MAPbI 3−x Cl x film, and reached to a maximum value about 12% in the case of 575 nm. Further thickening of the perov skite film was found to deteriorate the device performance because of the increase of surface roughness of the perovskite film and the inferior contact between electron transport layer (ETL) and thick active layer. Owning to the increased difficulty in controlling the morphology of the thick perovskite film and the resulting limited carrier diffusion lengths, poor charge extraction, serious charge recombination, it is rather hard to obtain thick film based high performance PVSCs as compared to those based on thinner junctions. To improve the morphology of the perovskite film with smooth and pinhole free surface, high crystallinity, High-performance perovskite solar cells (PVSCs) with absorber layer thickness insensitive features are important for practical fabrication, however these features are difficult to be realized. There are very few reports of the fabrication of polycrystalline PVSCs with power conversion efficienies (PCE) insensitive to film thickness beyond 600 nm. The main reason lies in more serious recombination of the thick perovskite layer compared to the thin layer. Herein, this challenge is addressed by a simple hot casting method to formulate high-quality perovskite film with enlarged grain size, high carrier mobility, and reduced defects. It is found that increasing the temperature to 70 °C can dramatically increase the film thickness and enlarge the...

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Inverted-structure perovskite solar cells (PVSCs) applying NiO x as the hole transport layer (HTL) have attracted increasing attention. It is still a challenge to optimize the contact between NiO x and the perovskite layer and to suppress energy loss at the interface. In this study, interface engineering was carried out by modifying the NiO x layer with different polymers such as polystyrene, poly(methyl methacrylate) (PMMA), or poly[bis(4-phenyl)(2,4,6-trimethylphenyl)amine] (PTAA) to improve the surface contact between NiO x and the perovskite, to decrease the defect states, and to make the energy level alignment better. The NiO x /PMMA-based device presents a V oc as high as 1.19 V because of the improved interfacial contact and the interaction of the carbonyl and methoxy group with Pb 2+ . The NiO x /PTAA-based device with the structure ITO/NiO x / PTAA/(MAPbI 3 ) 0.95 (MAPbBr 2 Cl) 0.05 /PCBM/BCP/Ag exhibits the highest power conversion efficiency of 21.56% with a high V oc of 1.19 V. The enhanced performance can be attributed to the deepened highest occupied molecular orbital level of NiO x /PTAA, which matched well with that of the perovskite and suppressed interface energy loss as well. This work provides a facile approach for efficiently improving the V oc of NiO x -based PVSCs.

2D perovskites with alternating cations in the interlayer space (ACI) have raised increasing interest in the field of layered 2D perovskite solar cells (PVSCs). Herein, ACI quasi‐2D PVSCs with a chemical formula of C(NH2)3(CH3NH3)4Pb4I13 (n = 4) are fabricated by an antisolvent method assisted by a novel two‐step post‐treatment process, in which guanidinium thiocyanate (GASCN) and MACl (GA = guanidinium, MA = methylammonium) are utilized as post‐treatment reagents, sequentially. With the first‐step post‐treatment by GASCN, the grain gaps within the perovskite films are dramatically diminished, leading to increased alignment and well‐ordered crystal grains. Consequently, the power conversion efficiency (PCE) of the corresponding devices increases by more than 50% (from 8.62% to 13.13%). After the second‐step post‐treatment by MACl, the trap states in the perovskite films are passivated, and as a result the PCE of the PVSCs is further enhanced to 15.27%. This work provides the new method of two‐step post‐treatment for fabrication of high quality 2D PVSC films.