Showing papers by "Anyi Mei published in 2023"
TL;DR: In this paper, a depth-dependent post-treatment strategy is demonstrated to synergistically passivate defects and tune interfacial energy band alignment in mesoscopic perovskite solar cells.
Abstract: The printable mesoscopic perovskite solar cells consisting of a double layer of metal oxides covered by a porous carbon film have attracted attention due to their industrialization advantages. However, the tens‐of‐micrometer thickness of the triple scaffold leads to a challenge for perovskite to crystallize and for the charge carriers to separate and travel to the electrode, which limits the open circuit voltage (VOC) of such devices. In this work, a depth‐dependent post‐treatment strategy is demonstrated to synergistically passivate defects and tune interfacial energy band alignment. Two thiophene derivatives, namely 3‐chlorothiophene (3‐CT) and 3‐thiophene ethylenediamine (3‐TEA), are selected for the post‐treatment. Energy‐dispersive X‐ray spectroscopy proves that 3‐CT is uniformly distributed throughout the triple scaffold and effectively passivates the defects of the bulky perovskite, while 3‐TEA reacts rapidly with the loose perovskite in the carbon layer to form 2D perovskite, forming a type II energy band alignment at the perovskite/carbon interface. As a result, the defect‐assisted recombination is suppressed and the interfacial energy band is regulated, increasing the VOC to 1012 mV. The PCE of the devices is enhanced from 16.26% to 18.49%. This depth‐dependent post‐treatment strategy takes advantage of the unique structure and provides a new insight for reducing the voltage loss.
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TL;DR: In this paper , the conductivity and defect modulation of the mesoporous TiO2 (mp-TiO2 ) ETL via oxygen vacancy (OV) management by the reduction and oxidation treatment are reported.
Abstract: The low electrical conductivity and the high surface defect density of the TiO2 electron transport layer (ETL) limit the power conversion efficiency (PCE) of corresponding perovskite solar cells (PSCs). Here, the conductivity and defect modulation of the mesoporous TiO2 (mp-TiO2 ) ETL via oxygen vacancy (OV) management by the reduction and oxidation treatment are reported. Reduction treatment via reducing agent introduces abundant OVs into the TiO2 nanocrystalline particles on the surface and at the subsurface. The following oxidation treatment via hydrogen peroxide removes the surface OVs while remains the subsurface OVs, resulting in stratified OVs. The stratified OVs improve the conductivity of TiO2 ETL by increasing carrier donors and decrease nonradiative centers by reducing surface defects. Such synergy ensures the capability of mp-TiO2 as the well-performed ETL with improved energy level alignment, suppressed interface recombination, enhanced carrier extraction, and transport. As a result, printable hole-conductor-free carbon-based mesoscopic PSCs based on the modulated mp-TiO2 ETL demonstrate a highest reported PCE of 18.96%.
TL;DR: In this article , the dissolution behavior of formamidinium lead iodide (FAPbI3) together with lead iodides (PbI2) in amide solvents with regulated coordination ability at increasing temperature and under different molar ratio between FAI and PbII2 is studied.
Abstract: The photovoltaic, luminescence, and detector fields have witnessed the robust application prospects of solution-processed halide perovskites. Deep insights into solution could pave the way towards the precise crystallization control of halide perovskites for giving full play to the advantages of those materials. Here, the dissolution behavior of formamidinium lead iodide (FAPbI3) together with lead iodide (PbI2) in amide solvents with regulated coordination ability at increasing temperature and under different molar ratio between FAI and PbI2 is studied. The solvent coordination ability, temperature and FAI/PbI2 molar ratio demonstrate equivalent influence on the dissolution and increasing those factors tends to increase the solubility first and decrease it then for Pb compounds. We propose that there are interchangeable Pb solute forms including solvent-containing lead complexes and solvated lead halide fragments in solution and the interconversion of both solutes driven by the above factors brings the solubility change. The modulated dissolution affects the crystallization behaviors of FAPbI3 when preparing single crystals, nanocrystal dispersions and thin films, and allows for regulated crystallinity in printable mesoscopic solar cells which demonstrate a power conversion efficiency of 18.40%. This article is protected by copyright. All rights reserved.
TL;DR: In this article , the application of the sodium methanesulfinate (SMSI) as the modifier for the hole-conductor-free printable mesoscopic perovskite solar cell (p•MPSC) with a carbon electrode is reported.
Abstract: High‐performance perovskite solar cells require the modification of grain boundaries in the polycrystalline light absorbing layer and salt modifiers have contributed a lot toward this requirement. Herein, the application of the sodium methanesulfinate (SMSI) as the modifier for the hole‐conductor‐free printable mesoscopic perovskite solar cell (p‐MPSC) with a carbon electrode is reported. It is found that SMSI prevents the oxidization of iodine ions in the precursor and methanesulfinate coordinates more strongly than methanesulfonate with perovskite. The interaction between SMSI and perovskite brings improved crystallinity and reduced defects, and thereby suppresses nonradiative recombination in p‐MPSCs. At the same time, SMSI also shifts the Fermi level of perovskite downward and contributes to an optimized energy‐level alignment for promoted charge injection. By introducing the SMSI modifier, the power conversion efficiency of p‐MPSCs from 16.6% to 18.1% is successfully improved. The research indicates that the methanesulfinate anion is a promising candidate for salt modifier design serving high‐performance PSCs.
TL;DR: In this paper , a solvent strategy was used for improving the perovskite crystallization in the printable mesoscopic structure of CsPbBr3 and PbBr2, which exhibited a more uniform and controllable distribution.
Abstract: The CsPbBr3 perovskite solar cells (PSCs) display extensive potential due to their good thermal and humidity stability, but the presence of heterogeneous phases severely limits the further improvement of device performance. Phase‐pure monoclinic CsPbBr3 can be stabilized by using the printable mesoscopic device structure. However, it is challenging to obtain high‐quality perovskite crystals in such confined space. Herein, a solvent strategy is used for improving the perovskite crystallization in the printable mesoscopic structure. By using N‐methylformamide as the precursor solvent, the PbBr2 exhibits a more uniform and controllable distribution, which benefits the CsPbBr3 crystallization. As a result, the CsPbBr3 inside the pores showed obvious orientation at (100) lattice plane and (110) crystal plane. The efficiency of modified PSCs increases from 7.53% to 8.32%. Based on the device with effective area of 1 cm2, the PSCs obtain a power conversion efficiency of 5.62%. In addition, PSCs show no obvious attenuation after 1000 h of maximum power point tracking, displaying the excellent illumination stability.
TL;DR: In this paper , a polymer additive polyacrylonitrile (PAN) was introduced into the formamidinium (FA) based perovskite for defect modulation.
Abstract: The low cost and scalability advantages of printable mesoscopic perovskite solar cells (p‐MPSCs) are impaired by the issue of limited power conversion efficiency (PCE). Herein, the PCE of p‐MPSCs is improved by introducing the polymer additive polyacrylonitrile (PAN) into the formamidinium (FA)‐based perovskite for crystallization and defect modulation. PAN forms hydrogen bond and coordination bond with halide perovskite through its C≡N group. Such interactions improve the crystallization and filling of FA‐based perovskite in the mesoscopic scaffold and bring a long carrier lifetime by passivating defects. The synergy improves the PCE of p‐MPSCs from 16.80% to 18.33%. Meanwhile, the hydrophobic nature of PAN enhances the device's resistance against moisture. This work demonstrates that the polymer additive is a promising choice for breaking the PCE limit of p‐MPSCs.