Thermal-stable mixed-cation lead halide perovskite solar cells

As perovskite solar cells show tremendous potential for widespread applications, we find that adding inorganic thermal-stable cesium ions into MAPbI_3 results in significantly improves thermal stability. For un-encapsulated perovskite devices, the energy conversion efficiency maintains about 75% of its original value（over 15%） in the MA_（0.85）Cs_（0.05）PbI_3 device under 80 min of heating at 140°C in a dry atmosphere（RH ≤ 30%）. With significantly improved thermal stability achieved by a convenient process, it is expected that this type of mixed-cation perovskites can further facilitate large scale applications.

Synergistic improvement of perovskite film quality for efficient solar cells via multiple chloride salt additives

Perovskite crystal film quality is critical for obtaining efficient perovskite solar cells. Anti-solvent processing was used for fast crystallization of perovskite precursor film, which can form dense perovskite film. However, the crystals from this method are usually small due to the fast crystal growth process, which could lead to grain boundary recombination. Here, element chloride is introduced to enhance the perovskite layer crystallinity via slowing down the perovskite crystallization process by simultaneous introduction of methylammounium chloride （MACI） and cesium chloride （CsCl） into precursor solution. As a result, we achieve high quality of pin-hole free perovskite film with large crystal size. A power conversion efficiency of 21.55% with free of hysteresis of the device is obtained, which is among the highest efficiency of planar structure perovskite solar cells.

Eliminating Hysteresis of Perovskite Solar Cells with Hollow CO_(2) Mesoporous Electron Transport Layer

Current density-voltage(J-V) hysteresis issue caused by unbalanced charge transport has greatly limited the improvement of power conversion efficiency(PCE) of halide perovskite solar cells(PSCs). Herein, hollow TiO2 mesoporous electron transport layer(ETL) was used to fabricate PSCs. The structure-dependent charge collection as well as its effect on PCE and hysteresis impactor(HI) of PSC were investigated. The results demonstrate that TiO2 hollow spheres in a size of around 50 nm (HS-50) can form a high quality perovskite/ETL interface with a less trap density. Moreover, the hollow TiO2 with the thin shell can help promote the extraction of electrons from perovskite layer to ETL, so as to reduce the charge accumulation and recombination at the perovskite/ETL interface and alleviate the hysteresis behavior. As a result, PSCs with HS-50 TiO2 delivered a champion PCE of 16.81% with a small HI of 0.0297, indicating a better performance than the commercial P25(PCE of 15.87%, HI of 0.2571).

Could two-dimensional perovskites fundamentally solve the instability of perovskite photovoltaics

The high efficiency and low production cost enable the halide perovskite solar cells as a promising technology for the next generation photovoltaics.Nevertheless,the relatively poor stability of the organic–inorganic halide perovskites hinders their commercial applications.In the past few years,two-dimensional(2D)perovskite has emerged as a more stable alternative to the three-dimensional(3D)counterparts and attracted intense research interests.Although many attempts and advances have been made,it is still ambiguous that whether the 2D perovskites could bring closure to the stability issue.To answer this essential question,a systematic study of the nature of 2D halide perovskites is necessary.Here,we focus on the stability investigations of 2D perovskites from different perspectives,especially light,heat,ion migration and strain.Several remaining challenges and opening problems are also discussed.With further material and device engineering,we believe that the 2D perovskites would promote perovskite solar cells to a promising future.

The stability of inorganic perovskite solar cells:from materials to devices

Inorganic halide perovskite solar cells(IHPSCs)have become one of the most promising research hotspots due to to the excellent light and thermal stabilities of inorganic halide perovskites(IHPs).Despite rapid progress in cell performance in very recent years,the phase instability of IHPs easily occurs,which will remarkably influence the cell efficiency and stability.Much effort has been devoted to solving this issue.In this review,we focus on representative progress in the stability from IHPs to IHPSCs,including(i)a brief introduction of inorganic perovskite materials and devices,(ii)some new additives and fabrication methods,(iii)thermal and light stabilities,(iv)tailoring phase stability,(v)optimization of the stability of inorganic perovskite solar cells and(vi)interfacial engineering for stability enhancement.Finally,perspectives will be given regarding future work on highly efficient and stable IHPSCs.This review aims to provide a thorough understanding of the key influential factors on the stability of materials to highly efficient and stable IHPSCs.