Tengfei Kong

Bio: Tengfei Kong is an academic researcher from Sun Yat-sen University. The author has contributed to research in topics: Perovskite (structure) & Formamidinium. The author has an hindex of 2, co-authored 4 publications receiving 12 citations.

Stable Layered 2D Perovskite Solar Cells with an Efficiency of over 19% via Multifunctional Interfacial Engineering.

Abstract: Layered 2D perovskites have been extensively investigated by scientists with photovoltaics (PV) expertise due to their good environmental stability. However, a random phase distribution in the perovskite film could affect both the performance and stability of the devices. To overcome this problem, we propose multifunctional interface engineering of 2D GA2MA4Pb5I16 perovskite by employing guanidinium bromide (GABr) on top of it to optimize the secondary crystallization process. It is found that GABr treatment can facilitate to form a shiny and smooth surface of the 2D GA2MA4Pb5I16 film with excellent optoelectronic properties. Thus, we realize efficient and stable 2D perovskite solar cells (PSCs) with a champion power conversion efficiency (PCE) of 19.3% under AM 1.5G illumination. Additionally, the optimized device without encapsulation could retain 94% of the initial PCE for more than 3000 h after being stored under ambient conditions.

Hydrophobic Fluorinated Conjugated Polymer as a Multifunctional Interlayer for High-Performance Perovskite Solar Cells

Abstract: It is known that the perovskite/hole transport layer (HTL) interface is a great limit to achieving high-performance perovskite solar cells (PSCs). Aiming to solve this problem, we introduce a napht...

In Situ Perovskitoid Engineering at SnO 2 Interface toward Highly Efficient and Stable Formamidinium Lead Triiodide Perovskite Solar Cells.

Abstract: The black-phase formamidinium lead triiodide (α-FAPbI3) perovskite has turned out to be one of the most efficient light harvesting materials. However, the phase stability of FAPbI3 is a long-standing issue. Herein, we introduce a layer of tetrabutylammonium fluoride (TBAF) on SnO2, which would form an in situ layer of TBAPbI3 perovskitoid at the SnO2/FAPbI3 interface by interacting with PbI2. The results show that this strategy could improve the conductivity of SnO2, passivate the defects in perovskite, improve the phase stability of α-FAPbI3, and retard the nonradiative recombination in the device. As a result, we obtain a champion device with a power conversion efficiency of 23.1% under AM 1.5 G illumination of 100 mW/cm2. The unencapsulated devices can maintain excellent stability under illumination, thermal stress, and humidity conditions, respectively.

Temperature‐Reliable Low‐Dimensional Perovskites Passivated Black‐phase CsPbI3 toward Stable and Efficient Photovoltaics

Abstract: Low-dimensional (LD) perovskites can effectively passivate and stabilize 3D perovskites for high-performance perovskite solar cells (PSCs). Regards CsPbI3-based PSCs, the influence of high-temperature annealing on the LD perovskite passivation effect has to be taken into account due to fact the black-phase CsPbI3 crystallization requires high-temperature treatment, however, which has been rarely concerned so far. Here, the thermal stability of LD perovskites based on three hydrophobic organic ammonium salts and their passivation effect toward CsPbI3 and the whole device performance, have been investigated. It is found that, phenyltrimethylammonium iodide (PTAI) and its corresponding LD perovskites exhibit excellent thermal stability. Further investigation reveals that PTAI-based LD perovskites are mainly distributed at grain boundaries, which not only enhances the phase stability of CsPbI3 but also effectively suppresses non-radiative recombination. As a consequence, the champion PSC device based on CsPbI3 exhibits a record efficiency of 21.0 % with high stability.

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

Abstract: 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.

Advances and Challenges in Two-Dimensional Organic-Inorganic Hybrid Perovskites Toward High-Performance Light-Emitting Diodes

Abstract: Two-dimensional (2D) perovskites are known as one of the most promising luminescent materials due to their structural diversity and outstanding optoelectronic properties. Compared with 3D perovskites, 2D perovskites have natural quantum well structures, large exciton binding energy (Eb) and outstanding thermal stability, which shows great potential in the next-generation displays and solid-state lighting. In this review, the fundamental structure, photophysical and electrical properties of 2D perovskite films were illustrated systematically. Based on the advantages of 2D perovskites, such as special energy funnel process, ultra-fast energy transfer, dense film and low efficiency roll-off, the remarkable achievements of 2D perovskite light-emitting diodes (PeLEDs) are summarized, and exciting challenges of 2D perovskite are also discussed. An outlook on further improving the efficiency of pure-blue PeLEDs, enhancing the operational stability of PeLEDs and reducing the toxicity to push this field forward was also provided. This review provides an overview of the recent developments of 2D perovskite materials and LED applications, and outlining challenges for achieving the high-performance devices.