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Active layers of p–i–n organic–inorganic hybrid perovskite solar cells (PSCs) are passivated by star‐shape, multifunctional triazinane molecules, cyanuric acid (CA), and Tris(dibutylhydroxy‐ benzyl)isocyanuric acid (TPCA). The most interesting is that CA is used as a bulk additive is able to induce a two‐dimensional (2D) structure at grain boundaries (GBs) of the perovskite when excess PbI2 is present. TPCA is also important to use as a perovskite surface modifier and to reduce the defects in perovskite layer further. The reduced ideality factors, enhanced photoluminescence, and prolonged lifetimes all indicate suppression of non‐radiative recombination. The combination of the two substantially improves fill‐factors and open‐circuit voltages of the devices. This leads to markedly enhanced stabilities of the devices. [ABSTRACT FROM AUTHOR]

The interfacial or bulk defects of the perovskite layer are important factors that affect the stability and photoelectric conversion efficiency of perovskite solar cells (PSCs). Herein, a multifunctional amino alcohol, 2,2‐Bis (3‐amino‐4‐hydroxyphenyl) hexafluoro propane (BHF), C15H12F6N2O2, is used as an additive of the active layer in p–i–n organic–inorganic halide perovskite solar cells. The BHF additive passivates perovskite predominately at grain boundaries. This additive leads to a vertically aligned crystal grain and reduced defect densities. The BHF‐treated perovskite films show suppressed nonradiative recombination with enhanced photoluminescence, longer carrier lifetimes, and reduced ionic migration. The device doped with 1 mg mL−1 BHF is able to improve power conversion efficiency to 20.30% (from 16.83% of the control), mainly due to the improvement of open‐circuit voltage. In addition, BHF passivation generates a more stable perovskite structure, resulting in improved operational stability of the PSCs. [ABSTRACT FROM AUTHOR]

A donor–acceptor (D–A)‐type discotic organic material (TP‐2‐PIE), having a self‐organization ability, is selected to be the third component blending with poly[4,8‐bis(5‐(2‐ethylhexyl)thiophen‐2‐yl)benzo[1,2‐b:4,5‐b']dithiophene‐co‐3‐fluorothieno [3,4‐b]‐thiophene‐2‐carboxylate] (PTB7‐Th): [6,6]‐phenyl‐C71‐butyric acid methyl ester (PC71BM) in ternary bulk‐heterojunction polymer solar cells. The complementary absorption and energy transfer between TP‐2‐PIE and PTB7‐Th contributes to the enhancement in photocurrent generation, improving the short‐circuit current. In addition, TP‐2‐PIE alters the molecular interaction leading to an enhanced phase separation, which promotes carrier transport with a good balance and minimizes the density of trap states simultaneously. In this way, the overall photovoltaic performances are markedly enhanced at an optimal condition of 10 wt% TP‐2‐PIE in donors with a 12.6% efficiency increase. Current understanding on the functionality of this third component in ternary solar cells may be able to guide future device development. [ABSTRACT FROM AUTHOR]

Even though the perovskite material itself has a high defect tolerance compared with other semiconductors, the defects existing at grain boundaries (GBs) or the surface still cause high densities of the trap state which impair the efficiency and stability of perovskite solar cells (PSCs). Herein, the small molecule 1,2‐benzisothiazolin‐3‐one (BIT) is investigated to passivate the defects at the GBs and surface of perovskite films. The results reveal that the BIT molecule belongs to a type of bifunctional species, which functions as cations and anions to passivate the perovskite surface. The BIT passivation generates lower formation energy and a more stable perovskite structure, resulting in improved performance and stability of the PSCs. The power conversion efficiency (PCE) of the optimized inverted photovoltaic device reaches 21.83%. Meanwhile, high photostability is achieved for PSCs with an efficiency drop of less than 10% under continuous light illumination over 500 h. [ABSTRACT FROM AUTHOR]

Ion migration is a crucial factor influencing the stability of perovskite solar cells. Insertion of an interfacial layer between the electron‐transporting layer and the cathode is shown to be an effective way to enhance the performance of devices. However, exploring more effective interfacial materials to block ion migration and thus enhance the device stability is still needed. Herein, a series of 8‐hydroxyquinoline metal complexes are employed as cathode interfacial layers (CILs) in inverted planar perovskite solar cells. The devices with CILs exhibit better performance, stability, and reproducibility than the control device without CILs. The introduction of the CILs forms a better energy match between the [6,6]‐phenyl‐C61‐butyric acid methyl ester layer and the cathode, reduces the contact resistance, accelerates the charge transfer, and suppresses non‐radiative recombination. Moreover, the CILs protect the device from moisture and block the ion diffusions, which is beneficial for device stability. After optimization, the best power conversion efficiency of 20.6% is obtained by using 8‐hydroxyquinoline aluminum (Alq3) as a CIL, and the efficiency remains 85% of its initial value after 800 h continuous illumination. [ABSTRACT FROM AUTHOR]

The instability of 3D perovskite and the low power conversion efficiency (PCE) of 2D perovskite limit the development of perovskite solar cells (PSCs). Using 2D perovskite to passivate 3D perovskite thin films by heterojunction engineering has become an effective strategy to develop stable and efficient PSCs. Therefore, it is important to find suitable 2D perovskite passivation materials. Herein, a 2D/3D heterojunction perovskite is formed in situ by introducing a long‐chain alkyl phenylbutylammonium (PBA+) cation. The 2D perovskite has the property of n = 2, which passivates the surface defects of the 3D perovskite, resulting in enhanced photoluminescence intensity and prolonged carrier lifetime. Moreover, the 2D layer changes the interface contact and energy‐level arrangement, making it a more n‐type semiconductor, which facilitates the electron transfer between perovskites and electron transport. This strategy significantly improves the open circuit voltage (Voc) and fill factor (FF) of the devices without sacrificing current, and the PCE is improved from 19.22% to 21.76%. The hydrophobic PBA+‐based 2D layer also improves the humidity stability of the films and enhances the working stability of the device. The PCE of the champion heterojunction perovskite device remains 87% of its initial value after illumination for 1000 h. The results show that heterojunction engineering plays an important role in the preparation of efficient and stable PSCs. [ABSTRACT FROM AUTHOR]

High‐quality perovskite films with low defect densities and high carrier‐diffusion lengths are essential for high‐performance perovskite devices. Herein, a modified two‐step sequential method is proposed, in which equal amounts of Cs+ and Rb+ ions (Cs+Rb+) are added to a PbI2 solution in the first step of perovskite deposition. The incorporation of Cs+Rb+ results in trace amounts of δ‐CsPbI3, leading to a reduction in the grain size in the PbI2 layer that facilitates better penetration of the organic salts in the second step of the precursor deposition. Meanwhile, the low density of the δ‐CsPbI3 crystals act as seeds to regulate the nucleation and growth of the perovskite crystals. A single‐layered columnar large‐grain perovskite film is obtained. The addition of Cs+Rb+ promotes crystal growth along the (100) orientation, which is beneficial for the reduction of surface defects. The incorporated Rb+ ions can regulate the remaining PbI2 in the perovskite. The improved quality of the perovskite film results in a significantly prolonged carrier lifetime of ≈7.01 μs and an enhanced electron diffusion length of ≈2.84 μm. As a result, the photovoltaic parameters are all improved in the established devices and a power conversion efficiency of 21.49% is reached. [ABSTRACT FROM AUTHOR]

A double‐layered poly(ethylenimine) ethoxylated (PEIE)/SnO2 composite structure, the ultrathin PEIE in contact with an indium‐tin‐oxide electrode, and an SnO2 layer interfaced with the perovskite, is developed as an electron‐transport layer (ETL) in the preparation of perovskite solar cells. The surface energy and the work function of the top SnO2 side of the composite ETL can be finely adjusted by tuning the underneath polyelectrolyte PEIE layer. These control the nucleation process in the crystallization of the perovskite layer and reduce the energy level mismatch between the electron transport and perovskite layers. High performance perovskite solar cells having a certified power conversion efficiency of 21.3%, with negligible hysteresis are achieved. [ABSTRACT FROM AUTHOR]

While perovskite light-emitting diodes typically made with high work function anodes and low work function cathodes have recently gained intense interests. Perovskite light-emitting devices with two high work function electrodes with interesting features are demonstrated here. Firstly, electroluminescence can be easily obtained from both forward and reverse biases. Secondly, the results of impedance spectroscopy indicate that the ionic conductivity in the iodide perovskite (CH3NH3PbI3) is large with a value of ≈10−8 S cm−1. Thirdly, the shift of the emission spectrum in the mixed halide perovskite (CH3NH3PbI3−xBrx) light-emitting devices indicates that I− ions are mobile in the perovskites. Fourthly, this work shows that the accumulated ions at the interfaces result in a large capacitance (≈100 μF cm−2). The above results conclusively prove that the organic–inorganic halide perovskites are solid electrolytes with mixed ionic and electronic conductivity and the light-emitting device is a light-emitting electrochemical cell. The work also suggests that the organic–inorganic halide perovskites are potential energy-storage materials, which may be applicable in the field of solid-state supercapacitors and batteries. [ABSTRACT FROM AUTHOR]

Perovskite Solar Cells: Additional Organic-Solvent-Rinsing Process to Enhance Perovskite Photovoltaic Performance (Adv. In combination with low-temperature annealing and organic-solvent rinsing at the surface of a perovskite intermediate, it is possible to recrystallize into larger sizes and induce PbI SB 2 sb passivation, as demonstrated by Zhiqun He and coworkers in article number 1900244. This process leads to a substantial enhancement in solar-cell performance. [Extracted from the article]