Multifunctional interfacial molecular bridge enabled by an aggregation-induced emission strategy for enhancing efficiency and UV stability of perovskite solar cells

The interface defects between the electron transport layer(ETL)and the perovskite layer,as well as the low ultraviolet(UV)light utilization rate of the perovskite absorption layer,pose significant challenges for the commercialization of perovskite solar cells(PSCs).To address this issue,this paper proposes an innovative multifunctional interface modulation strategy by introducing aggregation-induced emission(AIE)molecule 5-[4-[1,2,2-tri[4-(3,5-dicarboxyphenyl)phenyl]ethylene]phenyl]benzene-1,3-dicarboxylic acid(H_(8)ETTB)at the SnO_(2)ETL/perovskite interface.Firstly,the interaction of H_(8)ETTB with the SnO_(2)surface,facilitated by its carboxyl groups,is effective in passivating surface defects caused by noncoord inated Sn and O vacancies.This interaction enhances the conductivity of the SnO_(2)film and adjusts energy levels,leading to enhanced charge carrier transport.Simultaneously,H_(8)ETTB can passivate noncoord inated Pb^(2+)ions at the perovskite interface,promoting perovskite crystallization and reducing the interface energy barrier,resulting in a perovskite film with low defects and high crystalline quality.More importantly,the H_(8)ETTB molecule,can convert UV light into light absorbable by the perovskite,thereby reducing damage caused by UV light and improving the device's utilization of UV.Consequently,the champion PSC based on SnO_(2)-H_(8)ETTB achieves an impressing efficiency of 23.32%and significantly improved photostability compared with the control device after continuous exposure to intense UV radiation.In addition,the Cs_(0.05)(FA_(0.95)MA_(0.05))_(0.95)Pb(I_(0.95)Br_(0.05))_(3)based device can achieve maximum efficiency of 24.01%,demonstrating the effectiveness and universality of this strategy.Overall,this innovative interface bridging strategy effectively tackles interface defects and low UV light utilization in PSCs,presenting a promising approach for achieving highly efficient and stable PSCs.

UV light absorbers executing synergistic effects of passivating defects and improving photostability for efficient perovskite photovoltaics

Metal halide perovskite-based solar cells(PSCs) have rapidly-increased power conversion efficiency(PCE)exceeding 25% but poor stability especially under ultraviolet(UV) light. Meanwhile, non-radiative recombination caused by diverse defects in perovskite absorbers and related interfaces is one of the major factors confining further development of PSCs. In this study, we systematically investigate the role of 2-(2-hydroxy-5-methylphenyl)benzotriazole(UVP) additive in perovskite layers. By adjusting the amount of doped UVP, the quality of perovskite absorbers is significantly improved with enlarged grains, longer lifetime and diffusion length of charge carriers. Furthermore, UVP not only reduces defects for less nonradiative recombination, but also matches energy level alignment for efficient interfacial charge extraction. X-ray photoelectron spectroscopy confirms that N-donor of UVP molecule coordinates with undercoordinated Pb^(2+) on the surface. Interestingly, UVP incorporated in PbI_(2) protects the perovskite by absorbing UV through the opening and closing of the chelating ring. Eventually, the UVP treated PSCs obtain a champion PCE of 22.46% with remarkably enhanced UV stability, retaining over 90% of initial PCE after 60 m W/cm^(2) strong UV irradiation for 9 h while the control maintaining only 74%. These results demonstrate a promising strategy fabricating passivated and UV-resistant perovskite materials simultaneously for efficient and stable perovskite photovoltaics.

TiO^(2)electron transport bilayer for all-inorganic perovskite photodetectors with remarkably improved UV stability toward imaging applications

High ultraviolet(UV)stability and low dark current(Idark)are necessary for high-quality perovskite photodetectors(PDs).TiO^(2)thin film is known as effective electron-transport-layer(ETL)for perovskite devices.However,common spin-coated TiO^(2)ETLs endow many surface defects and have strong UV photocatalytic effect to decompose perovskite materials,resulting in inferior stability of devices.In this work,TiO^(2)bilayer film(Bi-TiO^(2))has been fabricated by combining spin-coating and atomic-layer-deposition process and its positive effects on UV stability and Idarkof Cs2 AgBiBr6-based PDs have been revealed for the first time.It is demonstrated that Bi-TiO^(2)possesses fewer surface defects and smoother morphology with type II band alignment,which is beneficial to suppress photocatalytic activity of TiO^(2)and reduce carrier recombination at the interface.After accelerated strong UV aging treatment,the PD with Bi-TiO^(2)maintains excellent performance,whereas the PD with spin-coated TiO^(2)film dramatically deteriorate with on-off ratio drops from~102 to~2.Besides,the Idarkof PD remarkably decreases from~10^(-8) A to~10^(-10) A after bilayer optimization.Furthermore,we have integrated the corresponding PDs into a self-built imaging system adopting diffuse reflection mode.This work suggests a feasible approach to fabricate TiO^(2)/Cs2 AgBiBr6-based PDs with remarkable UV tolerance for imaging applications.

Improving UV stability of perovskite solar cells without sacrificing efficiency through light trapping regulated spectral modification

The stability of perovskite solar cells is an important issue to be addressed for future applications.Perovskite solar cells are vulnerable to exposure to UV light due to promoted chemical reactions.However, preventing UV light from entering solar cells lowers the power conversion efficiency by reducing the photocurrent. The challenge is to improve UV stability without sacrificing efficiency. Here, we demonstrate the reduction of UV light-related negative effects from the perspective of spectral modification. By simultaneously introducing UV–visible downshifting and light trapping, perovskite solar cells can achieve a comparable efficiency of over 21% to that of an unmodified device. The optimized device obtains increased UV stability due to UV–visible downshifting. Different from other strategies, spectral modification externally alters the composition of incident light and improves UV stability without changing the internal device architecture, which is broadly applicable to perovskite solar cells with different structures. The present work may also find applications in other types of solar cells to boost the stability of devices exposed to UV light.

Fabrication of intercalated p-aminobenzoic acid into Zn-Ti layered double hydroxide and its application as UV absorbent

An organic ultraviolet （UV） ray absorbent, p-aminobenzoic acid （PABA） was intercalated into a Zn-Ti layered double hydroxide （LDH） precursor by an anion-exchange reaction to obtain ZnTi-PABA-LDH, a new organic-inorganic nanocomposite. The structure and the thermal stability of ZnTi-PABA-LDH were characterized by XRD, FT-IR and TG-DTA. The results indicate ZnTi-PABA-LDH, synthesized by this method, exhibit relatively high crystallinity, and markedly enhanced thermal stability of PABA after intercalation into ZnTi-LDH. The UV-vis-NIR spectrophotometric and ESR data show excellent UV ray resistance and greatly decreased photocatalytic activity when PABA is intercalated into the interlayers of the ZnTi-LDH. The studies suggest that ZnTi-PABA-LDH may have potential applications as safe sunscreen materials.

Nanophotonic-structured front contact for high-performance perovskite solar cells

We report the design of a nanophotonic metaloxide front contact aimed at perovskite solar cells(PSCs)to enhance optoelectronic properties and device stability in the presence of ultraviolet(UV)light.High-quality Cr-doped ZnO film was prepared by industrially feasible magnetron sputter deposition for the electron transport layer of PSCs.As a means,the influence of the Cr content on the film and device was systematically determined.In-depth device optics and electrical effects were studied using advanced three-dimensional opto-electrical multiphysics rigorous simulations,optimizing the front contact for realizing high performance.The numerical simulation was validated by fabricating PSCs optimized to reach high performance,energy conversion efficiency(ECE)=17.3%,open-circuit voltage(V_(OC))=1.08 V,short-circuit current density(J_(SC))=21.1 mA cm^(-2),and fillfactor(FF)=76%.Finally,a realistic front contact of nanophotonic architecture was proposed while improving broadband light absorption of the solar spectrum and light harvesting,resulting in enhanced quantum efficiency(QE).The nanophotonic PSC enables J_(SC)improvement by~17%while reducing the reflection by 12%,resulting in an estimated conversion efficiency over 23%.It is further demonstrated how the PSCs’UV-stability can be improved without considerably sacrificing optoelectronic performances.Particulars of nanophotonic designed ZnO:Cr front contact,PSCs device,and fabrication process are described.