Multi-site anchoring of single-molecule for efficient and stable perovskite solar cells with lead shielding

The emergence of perovskite solar cells(PSCs) has greatly promoted the progress of photovoltaic technologies.The rapid development of PSCs has been driven by the advances in optimizing perovskite films and their adjacent interfaces.However,the polycrystalline perovskite layers in most highly efficient PSCs still contain various defects that greatly limit photovoltaic performance and stability of the devices.Herein,we introduce a multifunctional additive ethylene diamine tetra methylene phosphonic sodium(EDTMPS) with multiple anchor points into the precursor of perovskite to improve the efficiency and stability of PSCs and provide in-situ protection of lead leakage.The addition of EDTMPS acts as a crystal growth controller and passivation agent for perovskite films,thereby slowing down the crystallization rate of the film and obtaining high-quality perovskite films.Our study also provides an insight into how the modifier modulate the interfacial energy level arrangement as well as affect transfer of charge carriers and their recombination under photoinduced excitation.As a result,the power conversion efficiency(PCE) of single subcell with a working area of 0.255 cm^(2) increases significantly from 20.03% to 23.37%.Moreover,we obtained a PCE of 19.16% for the 25 cm^(2) module.Importantly,the unencapsulated EDTMP-modified PSCs exhibit better operational and thermal stability,as well as in-situ absorption of leaked lead ions.

Incorporation ofγ-aminobutyric acid and cesium cations to formamidinium lead halide perovskites for highly efficient solar cells

The stability issue has become one of the main challenges for the commercialization of perovskite solar cells(PSCs).Formamidinium(FA)-based perovskites have shown great promise owing to their improved thermal and moisture stability.However,these perovskites are suffering from phase transition and separation.Here,a method of incorporating of γ-aminobutyric acid(GABA) and cesium cations into FAPbl_(3) is developed to improve the phase stability.It is demonstrated that the crystallinity of α-FAPbl_(3) phase is greatly improved and the phase transition temperature is significantly dropped.The resultant solar cell therefore obtains a champion power conversion efficiency(PCE) of 23.71%,which is one of the highest efficiencies for methylammonium-free PSCs.Furthermore,it shows an impressively enhanced stability under illumination,exhibiting the great potential of FA-based perovskites for efficient and stable solar cells.

Investigation on the adhesive contact and electrical performance for triboelectric nanogenerator considering polymer viscoelasticity

The triboelectric nanogenerator(TENG)is a new mechanical energy harvesting technology in which the typical viscoelastic material polydimethylsiloxane(PDMS)is widely used.Micro-/nano-textures are often fabricated on the PDMS surface to enhance the electrical performance of TENG.As the contact region decreases to micro/nano scale,the adhesive forces become dominant.However,there is still a lack of contact mechanics model considering both material viscoelasticity and the adhesive forces to guide the surface texture design.In this paper,the explicit data-fitting formulas based on the fractional derivative Zener model are firstly derived to identify the viscoelastic constitutive parameters,which can not only avoid the influence of the initial contact point,but also ensure the accurate conversion between the creep compliance and the relaxation modulus function.Then a viscoelastic-adhesive contact model based on the fitted constitutive parameters is established,and the numerical algorithms such as bi-conjugate stabilized(Bi-CGSTAB)method and fast Fourier transform(FFT)technique are employed to analyze the effects of material viscoelasticity and texture sizes on the contact and electrical performance.It is shown that,compared with results from the elastic-adhesive contact model,the contact area ratio based on the viscoelastic-adhesive contact model is significantly larger,which is much closer to the experimental results.Among the selected sizes of pyramid texture,the higher electrical performance can be obtained from the textures with a smaller pitch and a larger width under the heavier applied load.This study can provide a theoretical reference for the design of viscoelastic surface texture of TENG.

Low temperature fabrication for high-performance semitransparent CsPbI_(2)Br perovskite solar cells

All-inorganic CsPbI_(2)Br perovskite with suitable bandgap and excellent thermal stability has been reported as the most promising candidate for efficient perovskite solar cells (PSCs). However, the high annealing temperature (> 250 ℃) and poor stability of α-CsPbI_(2)Br greatly limit the future application in photovoltaic field. Herein, a facile method is reported to prepare α-CsPbI_(2)Br perovskite film with high stability at low temperature (70 ℃) by incorporating a small amount of γ-aminobutyric acid (GABA) in the precursor solutions. The devices exhibit reproducible photovoltaic performance with a champion efficiency up to 15.16%, along with the excellent stability, maintaining more than 80% of its initial efficiency after stored in ambient condition for 600 h without any encapsulation. Most importantly, the method enables fabrication of semitransparent CsPbI_(2)Br PSCs with a PCE of 6.76%, as well as an average visible transparency (AVT) of 25.38%. To the best of our knowledge, this is the first attempt to apply CsPbI_(2)Br to the semitransparent solar cells.