Search

Wide‐bandgap (WBG) perovskite solar cells (PSCs) have garnered significant attention for their potential applications in tandem solar cells. However, their large open‐circuit voltage (VOC) deficit and serious photo‐induced halide segregation remain the main challenges that impede their applications. Herein, a post‐treatment strategy without thermal annealing is presented to form a 2D top layer of 2‐thiopheneethylammonium lead halide (n = 1) on WBG perovskites. This thermal annealing‐free post‐treatment method can more effectively passivate the defects of WBG methylamine (MA)‐free formamidinium/cesium lead iodide/bromide perovskite films and suppress photo‐induced perovskite phase segregation, as compared with the thermal annealing method that yields multi‐2D phases. The resulting opaque and semi‐transparent 1.66 eV‐bandgap perovskite solar cells deliver maximum power conversion efficiencies of 21.47% (a small VOC deficit of 0.43 V) and 19.11%, respectively, both of which are among the highest reports for inverted MA‐free WBG PSCs. Consequently, four‐terminal all‐perovskite tandem cells realize a remarkable efficiency of 26.64%, showing great promise for their applications in efficient multi‐junction tandem solar cells. [ABSTRACT FROM AUTHOR]

Quasi‐two‐dimensional (quasi‐2D) perovskite light‐emitting diodes (PeLEDs) are considered as one of the most potential candidates in electroluminescence territory owing to their unique quantum confinement effect and excellent thermal stability of the light. Nevertheless, heterogeneous energy domain distribution leads to severe non‐radiative recombination in the process of energy transfer, which enormously hinders the performance and application of PeLEDs. Herein, an ambipolar amino acid, 5‐aminovaleric acid (5AVA), is demonstrated to be able to coordinate lead and halides simultaneously with its carboxyl and amidogen groups. The coordinated ambipolar molecule not only reconstitutes energy domains of perovskites but also minimizes the interfacial defects of PeLEDs. Accordingly, the presence of 5AVA in perovskite precursors leads to dramatic suppression of the n = 1 and n = 2 phases and accelerates energy transfer from wide bandgap domains to narrow bandgap ones. As a result, maximum external quantum efficiency (EQE) of 19.3% (18.20% ± 1.10%) is achieved in quasi‐2D green PeLEDs with current efficiency of 61.7 cd A−1. [ABSTRACT FROM AUTHOR]

External encapsulation technique as a straightforward craft process has been adopted to prevent the infiltration of moisture and oxygen, thereby improving environmental stabilities of lead halide perovskite solar cells (PSCs). However, irreversible light‐induced degradation originating from various vacancies and ion diffusion or migration inside the device cannot be efficiently solved by external encapsulation. Herein, an internal encapsulation strategy by introducing NbCl5 at the buried tin oxide/perovskite interface and spin‐casting n‐butylammonium bromide on top of perovskite is developed to comprehensively passivate the vacancies and hence block the channels for ion diffusion or migration. The internal encapsulation strategy results in better homogeneous electron transport layer and effective vacancy passivation at the buried interface and simultaneously generates a more homogeneous, better crystallized perovskite in the vertical direction with significantly reduced residual PbI2. Furthermore, fewer oxygen vacancies and formation of ultrathin Nb2O5 lead to a better interfacial energy level alignment for electron transfer. As a result, power conversion efficiency (PCE) of the resulting PSCs is as high as 24.01%. More importantly, the device demonstrates an excellent stability, retaining 88% of its initial PCE at its maximum power point tracking measurement (under 100 mW cm–2 white light illumination at ≈55 °C temperature, in N2 atmosphere) after 1000 h. [ABSTRACT FROM AUTHOR]

Trap‐induced nonradiative recombination and decomposition are the major limiting factors that hinder the development of mixed‐halide wide‐bandgap perovskite solar cells. Specifically, the incorporation of formamidinium (FA+) and bromide in wide‐bandgap (WBG) perovskite materials leads to shallow‐energy‐level traps and inferior light stability. Herein, the electron‐withdrawing molecule 2,3,5,6 tetrafluoro‐7,7,8,8‐tetracyanoquinodimethane (F4‐TCNQ) is used as an effective passivator and stabilizer, which has molecular interaction with the FA+ cation for reducing trap densities and enhancing the stability of WBG perovskite solar cells. It is found that the extended π aromatic system in F4‐TCNQ can enhance the binding energy and stabilize the FA+ cation in perovskite films. Furthermore, the 1.67 eV bandgap inverted perovskite solar cells with a small amount of F4‐TCNQ have shallower defect levels, reduced trap density, and decreased nonradiative recombination, therefore giving a remarkably improved power conversion efficiency (PCE) of 20.0%. Most importantly, the unencapsulated devices with F4‐TCNQ additive have greatly enhanced stability, maintaining 88% of their peak PCEs under continuous illumination after 840 h, whereas the control devices only retain 48% of their PCEs after 500 h. [ABSTRACT FROM AUTHOR]

Metal halide perovskite nanocrystals (NCs) serve as a kind of ideal semiconductor for luminescence and display applications. However, the optoelectronic performance and stability of perovskite NCs are mainly subjected to current ligand strategies since these ligands exhibit a highly dynamic binding state, which complicates NC purification and storage. Herein, a method named diffusion‐induced extraction is developed for crystallization (DEC) at room temperature, in which silicone oil serves as a medium to separate the solvent from perovskite precursors and diethyl ether promotes the nucleation, leading to highly emissive perovskite NCs. The formation mechanism of NCs using this approach is elucidated, and their optoelectronic properties are fully characterized. The resultant NCs ink exhibits a high photoluminescence quantum yield (PLQY) over 90% with a narrow full width at half maximum of 17 nm. The DEC method strengthens the interaction between ligand and NCs via the hydrophobic silicone oil. Therefore, the NCs maintain almost 95% of their initial PLQYs after aging more than seven months in air. The findings will be of great significance for the continued advancement of high PLQY perovskite NCs through a better understanding of formation dynamics. The DEC strategy presents a major step forward for advancing the field of perovskite semiconductor nanomaterials. [ABSTRACT FROM AUTHOR]

β-NaYF 4 :Yb 3+ , Tm 3+ @ TiO 2 core-shell upconversion nanoparticles (UCNPs) were synthesized and incorporated into the TiO 2 mesoporous layer of perovskite solar cells (PSCs). Changes of the upconversion spectra of the UCNPs suggest the existence of the electron injection from NaYF 4 :Yb 3+ , Tm 3+ to the conduction band (CB) of TiO 2 through the NaYF 4 :Yb 3+ , Tm 3+ /TiO 2 nano-heterojunctions. The core-shell UCNPs that incorporated into the TiO 2 mesoporous layer not only act as the upconversion centers to use the NIR light but also serve as the light scatter centers to enhance the light harvesting. When using mesoporous layer containing the core-shell UCNPs in PSCs, the efficiency of the best devices is 16.27%, which is about 16.38% higher than that of the devices without core-shell UCNPs (13.98%). The significant enhancement in the performance of the PSCs is attributed to light scattering, NIR light upconversion and electron injection from the UCNPs to the CB of TiO 2 . [ABSTRACT FROM AUTHOR]

Mixed tin–lead (Sn–Pb) perovskites often face a daunting challenge: rapid and uncontrollable crystallization, leading to a plethora of defects and significant stress. This issue is particularly exacerbated during the blade‐coating preparation of scalable Sn–Pb perovskite films. In this study, a facile strategy involving the addition of ammonium citrate (AC) to narrow‐bandgap mixed Sn–Pb perovskite precursors is introduced. AC, armed with its arsenal of multiple carboxyl and amino groups, acts as a virtuoso conductor, orchestrating controlled crystal growth by harmonizing with Pb2+ and Sn2+ ions. This addition significantly boosts the crystallinity of the perovskite films, alleviates interface stress, inhibits Sn2+ oxidation, and mitigates interfacial defects. Consequently, The blade‐coated AC‐incorporated mixed Sn–Pb perovskite solar cells achieve a high photovoltaic conversion efficiency of nearly 21%. Furthermore, extending this strategy to two‐terminal all‐perovskite tandem solar cells yielded a remarkable maximum efficiency of 27.20%. This work presents an effective strategy for producing efficient blade‐coated mixed Sn–Pb perovskite solar cells, heralding a pathway toward scalable fabrication of all‐perovskite tandem solar cells. [ABSTRACT FROM AUTHOR]

• Molecular weight has a significant effect on the mobility and electrical conductivity of the PTPD. • The interfacial charge transferring and transport between the perovskite and PTPD varies with the PTPD' molecular weight. • We fabricate the inverted PSCs based on MAPbI 3 with a champion PCE of 19.24% with negligible hysteresis. Inverted planar perovskite solar cells (PSCs) with poly(N,N′-bis(4-butylphenyl)-N,N′-bis(phenyl)benzidine) (PTPD) layer as hole-transporting layer (HTL) exhibit high power conversion efficiencies (PCEs) over 20%. However, the influence of PTPD's molecular weight (Mw) on the performance of PSCs has not been reported yet. Herein, we employ PTPD with various molecular weights as HTL to fabricate highly efficient inverted planar PSCs. Our results show that PTPD with 75 kDa possesses superior conductivity, which can quicken the charge carrier extraction from perovskite to HTL. In addition, the MAPbI 3 perovskite film atop the 75-kDa PTPD is smoother with higher crystallinity and lower defect density. As a result, inverted planar PSCs with 75-kDa PTPD as HTL deliver a highest PCE of 19.24%. Our work provides a beneficial reference for future preparation of stable and highly efficient inverted PSCs with polymer HTL. [ABSTRACT FROM AUTHOR]

• 1. Bilayer ETL ZnO/Mg x Zn 1-x O and HTL dopant-free PM6 are introduced. • 2. ZnO/Mg x Zn 1-x O provides a cascaded energy level alignment with CsPbI 2 Br. • 3. ZnO/Mg x Zn 1-x O improves CsPbI 2 Br film quality. • 4. PM6 energetically aligns better with CsPbI 2 Br than spiro-OMeTAD. • 5. CsPbI 2 Br-based PSCs delivers a champion PCE over 16% with V OC deficit of 0.58 V. All-inorganic perovskite CsPbI 2 Br is a promising wide bandgap light absorber for tandem solar cells owing to its appropriate bandgap and great thermal stability. However, high open-circuit voltage (V OC) deficit has been a major obstacle for obtaining high efficiency in CsPbI 2 Br-based solar cells and thus limiting their application. Herein, we employ a strategy of interface engineering that deploys a bilayer electron transporting layer (ETL) and dopant-free hole transporting layer (HTL) to significantly mitigate the energy loss. A bilayer ETL ZnO/Mg x Zn 1-x O and Poly[(2,6-(4,8-bis(5-(2-ethylhexyl-3-fluoro)thiophen-2-yl)-benzo[1,2-b:4,5-b′]dithiophene))-alt-(5,5-(1′,3′-di-2-thienyl-5′,7′-bis(2-ethylhexyl)benzo[1′,2′-c:4′,5′-c′]dithiophene-4,8-dione)] (PM6) are energetically more compatible with the energy band of CsPbI 2 Br than ZnO and 2,2′,7,7′-tetrakis (N, N-di-p-methoxy-phenylamine)-9,9′-spirobifluorene (spiro-OMeTAD), which facilitate the photogenerated electron and hole transfer at perovskite/charge transporting layer interfaces. Moreover, the quality of the CsPbI 2 Br perovskite film deposited atop bilayer ETL ZnO/Mg x Zn 1-x O is substantially enhanced compared to that on top of ZnO. Both the more favorable energy level alignment and reduced defect density alleviate energy loss in the resultant solar cells. Perovskite solar cells with the structure of ITO/ZnO/Mg x Zn 1-x O/CsPbI 2 Br/PM6/MoO 3 /Ag give rise to an open-circuit voltage (V OC) of 1.34 V, which is one of the highest V OC among all-inorganic CsPbI 2 Br solar cells. The resultant V OC deficit drops to be lower than 0.6 V. As a result, the optimized all-inorganic CsPbI 2 Br-based solar cells yield a champion power conversion efficiency of 16.04%. [ABSTRACT FROM AUTHOR]