Haotian Wu

Bio: Haotian Wu is an academic researcher from Zhejiang University. The author has contributed to research in topics: Perovskite (structure) & Materials science. The author has an hindex of 3, co-authored 11 publications receiving 56 citations. Previous affiliations of Haotian Wu include South China University of Technology.

Additive‐Assisted Hot‐Casting Free Fabrication of Dion–Jacobson 2D Perovskite Solar Cell with Efficiency Beyond 16%

Abstract: Two-dimensional (2D) Dion-Jacobson (DJ) perovskite solar cells (PVSCs) with high PCE are currently predominately fabricated via a hot-casting process. While it is difficult to prepare high-quality perovskite film under mild conditions when the application of divalent ammonium. In this work, the morphology of the 2D DJ perovskite film was tuned with the aid of MASCN additive under room temperature spin-coating deposition conditions. The device with inverted planar structure presented a hero performance of JSC of 17.91 mA cm−2, Voc of 1.19 V, FF of 0.76 and PCE of 16.25%, which is the highest PCE ever reported for hot-casting free 2D DJ PVSCs.

Merged interface construction toward ultra-low Voc loss in inverted two-dimensional Dion–Jacobson perovskite solar cells with efficiency over 18%

Abstract: An optimized interface between a perovskite and a charge transport layer with full contact and low defect density favors an improvement in performance of perovskite solar cells (PVSCs). However, few works have been reported on constructing an interface for efficient charge transport and low energy loss in 2D Dion–Jacobson (DJ) PVSCs with an inverted structure. Herein, a deposition process combining pre-annealing and merged annealing (PMA) was demonstrated to be effective in constructing a merged interface between the layers of an electron transport material, PC61BM, and DJ perovskite (3AMP)(MA0.75FA0.25)3Pb4I13, which promotes perovskite/PC61BM contact and thus improves defect passivation and charge transport. A high Voc (1.24 V) with ultra-low energy loss (0.35 eV) is achieved because of the decreased defect density. A PMA-based device with a structure of ITO/(NiOx/PTAA)/perovskite/PC61BM/BCP/Ag exhibits a highest PCE of 18.67%, which is the highest value among the 2D DJ PVSCs with an inverted structure. The device retains 90% of its initial PCE after storage in air with a humidity of 45 ± 5% for 60 days or in an 85 °C N2 atmosphere for 480 h, and remains unchanged in 50 cycles of thermal cycling measurements. This work provides an effective approach towards 2D DJ PVSCs with both high efficiency and high moisture and thermal stability.

High‐Quality Ruddlesden–Popper Perovskite Film Formation for High‐Performance Perovskite Solar Cells

Abstract: In the last decade, perovskite solar cells (PSCs) have undergone unprecedented rapid development and become a promising candidate for a new-generation solar cell. Among various PSCs, typical 3D halide perovskite-based PSCs deliver the highest efficiency but they suffer from severe instability, which restricts their practical applications. By contrast, the low-dimensional Ruddlesden-Popper (RP) perovskite-based PSCs have recently raised increasing attention due to their superior stability. Yet, the efficiency of RP perovskite-based PSCs is still far from that of the 3D counterparts owing to the difficulty in fabricating high-quality RP perovskite films. In pursuit of high-efficiency RP perovskite-based PSCs, it is critical to manipulate the film formation process to prepare high-quality RP perovskite films. This review aims to provide comprehensive understanding of the high-quality RP-type perovskite film formation by investigating the influential factors. On this basis, several strategies to improve the RP perovskite film quality are proposed via summarizing the recent progress and efforts on the preparation of high-quality RP perovskite film. This review will provide useful guidelines for a better understanding of the crystallization and phase kinetics during RP perovskite film formation process and the design and development of high-performance RP perovskite-based PSCs, promoting the commercialization of PSC technology.

Surface Passivation Using 2D Perovskites toward Efficient and Stable Perovskite Solar Cells

Abstract: 3D perovskite solar cells (PSCs) have shown great promise for use in next-generation photovoltaic devices. However, some challenges need to be addressed before their commercial production, such as enormous defects formed on the surface, which result in severe SRH recombination, and inadequate material interplay between the composition, leading to thermal-, moisture-, and light-induced degradation. 2D perovskites, in which the organic layer functions as a protective barrier to block the erosion of moisture or ions, have recently emerged and attracted increasing attention because they exhibit significant robustness. Inspired by this, surface passivation by employing 2D perovskites deposited on the top of 3D counterparts has triggered a new wave of research to simultaneously achieve higher efficiency and stability. Herein, we exploited a vast amount of literature to comprehensively summarize the recent progress on 2D/3D heterostructure PSCs using surface passivation. The review begins with an introduction of the crystal structure, followed by the advantages of the combination of 2D and 3D perovskites. Then, the surface passivation strategies, optoelectronic properties, enhanced stability, and photovoltaic performance of 2D/3D PSCs are systematically discussed. Finally, the perspectives of passivation techniques using 2D perovskites to offer insight into further improved photovoltaic performance in the future are proposed.

Highly Efficient and Stable Dion−Jacobson Perovskite Solar Cells Enabled by Extended π-Conjugation of Organic Spacer

Abstract: 2D Dion-Jacobson (DJ) perovskites have become an emerging photovoltaic material with excellent structure and environmental stability due to their lacking van der Waals gaps relative to 2D Ruddlesden-Popper perovskites. Here, a fused-thiophene-based spacer, namely TTDMAI, is successfully developed for 2D DJ perovskite solar cells. It is found that the DJ perovskite using TTDMA spacer with extended π-conjugation length exhibits high film quality, large crystal size and preferred crystal vertical orientation induced by the large crystal nuclei in precursor solution, resulting in lower trap density, reduced exciton binding energy and oriented charge transport. As a result, the optimized 2D DJ perovskite device based on TTDMA (nominal n = 4) delivers a champion PCE up to 18.82%. Importantly, the unencapsulated device based on TTDMA can sustain average 99% of their original efficiency after being stored in N2 for 4400 h (over 6 months). Moreover, light, thermal, environmental and operational stabilities are also significantly improved in comparison with their 3D counterparts.

Insight on the Stability of Thick Layers in 2D Ruddlesden-Popper and Dion-Jacobson Lead Iodide Perovskites.

Abstract: Two-dimensional (2D) hybrid organic–inorganic halide perovskites are a preeminent class of low-cost semiconductors whose inherent structural tunability and attractive photophysical properties have ...