Simultaneous hydrogen production with the selective oxidation of benzyl alcohol to benzaldehyde by a noble-metal-free photocatalyst VC/CdS nanowires

As game-changers in the photovoltaic community, perovskite solar cells are making unprecedented progress while still facing grand challenges such as improving lifetime without impairing efficiency. Herein, two structurally alike polyaromatic molecules based on naphthalene-1,8-dicarboximide (NMI) and perylene-3,4-dicarboximide (PMI) with different molecular dipoles are applied to tackle this issue. Contrasting the electronically pull-pull cyanide-substituted PMI (9CN-PMI) with only Lewis-base groups, the push-pull 4-hydroxybiphenyl-substituted NMI (4OH-NMI) with both protonic and Lewis-base groups can provide better chemical passivation for both shallow- and deep-level defects. Moreover, combined theoretical and experimental studies show that the 4OH-NMI can bind more firmly with perovskite and the polyaromatic backbones create benign midgap states in the excited perovskite to suppress the damage by superoxide anions (energetic passivation). The polar and protonic nature of 4OH-NMI facilitates band alignment and regulates the viscosity of the precursor solution for thicker perovskite films with better morphology. Consequently, the 4OH-NMI-passivated perovskite films exhibit reduced grain boundaries and nearly three-times lower defect density, boosting the device efficiency to 23.7%. A more effective design of the passivator for perovskites with multi-passivation mechanisms is provided in this study.

Marked Passivation Effect of Naphthalene-1,8-Dicarboximides in High-Performance Perovskite Solar Cells

Passivation of electronic defects on the surface and at grain boundaries (GBs) of perovskite films has become one of the most effective tactics to suppress charge recombination in perovskite solar cells. It is demonstrated that trap states can be effectively passivated by Lewis acid or base functional groups. In this work, nicotinamide (NTM, commonly known as vitamin B3 or vitamin PP) serving as a Lewis base additive is introduced into the PbI2 and/or FAI: MABr: MACl precursor solution to obtain NTM modified perovskite films. It has been found that the NTM in the perovskite film can well passivate surface and GBs defects, control the film morphology and enhance the crystallinity via its interaction with a lone pair of electrons in nitrogen. In the presence of the NTM additive, we obtained enlarged perovskite crystal grain about 3.6 μm and a champion planar perovskite solar cell with efficiency of 21.72% and negligible hysteresis. Our findings provide an effective route for crystal growth and defect passivation to bring further increases on both efficiency and stability of perovskite solar cells.

Nicotinamide as Additive for Microcrystalline and Defect Passivated Perovskite Solar Cells with 21.7% Efficiency.

In recent years, 2D Ruddlesden-Popper (2DRP) perovskite materials have been explored as emerging semiconductor materials in solar cells owing to their excellent stability and structural diversity. Although 2DRP perovskites have achieved photovoltaic efficiencies exceeding 19%, their widespread use is hindered by their inferior charge-carrier transport properties in the presence of diverse organic spacer cations, compared to that of traditional 3D perovskites. Hence, a systematic understanding of the carrier transport mechanism in 2D perovskites is critical for the development of high-performance 2D perovskite solar cells (PSCs). Here, the recent advances in the carrier behavior of 2DRP PSCs are summarized, and guidelines for successfully enhancing carrier transport are provided. First, the composition and crystal structure of 2DRP perovskite materials that affect carrier transport are discussed. Then, the features of 2DRP perovskite films (phase separation, grain orientation, crystallinity kinetics, etc.), which are closely related to carrier transport, are evaluated. Next, the principal direction of carrier transport guiding the selection of the transport layer is revealed. Finally, an outlook is proposed and strategies for enhancing carrier transport in high-performance PSCs are rationalized. 

Charge‐Carrier Transport in Quasi‐2D Ruddlesden–Popper Perovskite Solar Cells

Perovskite solar cells (PSCs), with their low cost and simple fabrication, have emerged as promising devices to solve global warming issues. In this study, tetrabutylammonium tetrafluoroborate (TBABF4) was used as a passivator to boost the performance and the stability of the fabricated PSCs. Through TBABF4 post-treatment, the perovskite film's grain boundaries were passivated, which caused a reduction of charge traps on the surface of the perovskite layer and served as interfacial engineering at the perovskite/hole transport layer (HTL) interface. It was found that TBABF4 can act as a source of TBA+ cations and cause the formation of a 2D/3D heterostructure layer, which increases the stability of PSCs. Indeed, the 2D/3D structure derived from TBABF4 solution plays the role of a shield layer to protect the surface of the perovskite layer from degradation and facilitates charge transport processes. The post-treatment of perovskite films is, thus, introduced as an approach to address both the stability and the performance of PSCs and as a step forward to commercialize PSCs.

Fabrication of stable and efficient 2D/3D perovskite solar cells through post-treatment with TBABF4

Lead halide perovskite solar cells (PSCs) have been rapidly developed in the past decade. Owing to its excellent power conversion efficiency with robust and low-cost fabrication, perovskite quickly becomes one of the most promising candidates for the next-generation photovoltaic technology. With the development of PSCs, the interface engineering has witnessed its increasingly critical role in maximizing the device performance as well as the long-term stability, because the interfaces in PSCs are closely correlated with the defect management, carrier dynamics and surface passivation. This review focuses on interfacial modification between the perovskite active layer and the charge transport layer, as well as the recent advances on high-efficiency and stable PSCs driven by interface engineering strategies. The contributing roles of interface engineering in terms of defect passivation, inhibiting ion migration, optimization of energy band alignment and morphological control are discussed. Finally, based on the latest progress and advances, strategies and opportunities for the future research on interface engineering for PSCs are proposed to promote the development of perovskite photovoltaic technology.

Recent advances on interface engineering of perovskite solar cells

Self-healing perovskite solar cells

Wide‐bandgap (WBG) perovskite solar cells (PSCs) suffer from severe voltage loss, which significantly limits the enhancement of photovoltaic performance. Here, 4‐fluoro‐phenylethylammonium iodide (FPEAI) is used as a dual‐functional agent for oriented crystallization and comprehensive passivation of WBG PSCs. The additive of FPEAI promotes crystals to grow along with the (100) orientation with improved crystallinity and to spontaneously form Ruddlesden–Popper 2D perovskite on the grain boundary and surface of 3D crystals, which can passivate defects and protect the perovskite film from moisture erosion as well as suppressed ion migration. In addition, the 2D/3D heterostructure induces a matched energy‐level alignment, which mitigates the detrimental interfacial charge recombination at the interface of the 3D perovskite and hole transport layer. Consequently, the modified WBG PSCs exhibit an improved open‐circuit voltage to 1.3 V and a fill factor of 77.8%, leading to a remarkable power conversion efficiency of 19.1% with negligible hysteresis. Furthermore, the WBG PSCs maintain 85% of the original efficiency after 1000 h in air, demonstrating outstanding humidity stability. This work indicates that FPEAI can be used as a dual‐functional agent to significantly enhance the efficiency of WBG PSCs.

Synergetic Regulation of Oriented Crystallization and Interfacial Passivation Enables 19.1% Efficient Wide‐Bandgap Perovskite Solar Cells

Cesium (Cs) contained triple-cation and mixed halide perovskite (CsFAMA) is broadly employed as light absorption layers for efficient and stable perovskite solar cells (PSCs) fabrication with high ...

Hua Yu

Papers

Recent advances on interface engineering of perovskite solar cells

Self-healing perovskite solar cells

Synergetic Regulation of Oriented Crystallization and Interfacial Passivation Enables 19.1% Efficient Wide‐Bandgap Perovskite Solar Cells

Effects of Annealing Time on Triple Cation Perovskite Films and Their Solar Cells.

A Review on Gas-Quenching Technique for Efficient Perovskite Solar Cells