Xihong Ding

Temperature-assisted rapid nucleation: a facile method to optimize the film morphology for perovskite solar cells

The nucleation stage has an important influence on the lead halide perovskite film morphology, and therefore the solar cell performance. Here, we introduce a facile temperature-assisted rapid nucleation (TRN) method to improve the film crystallization process and the film morphology. By employing low temperature anti-solvents (diethyl ether, chlorobenzene and toluene), we stimulate homogeneous nuclei growth, resulting in a highly dense perovskite thin layer. The TRN method prepared (FAPbI3)0.85(MAPbBr3)0.15 devices exhibit a power conversion efficiency up to 19.2% and maintain over 85% of the original efficiency after 40 days of storage at room temperature under a relative humidity of 10–40%.

Facile fabrication of perovskite layers with large grains through a solvent exchange approach

Large-grained perovskite layers with fewer defects are beneficial to minimize carrier recombination at grain boundaries, thus boosting cell performance. Here, we present a facile solvent exchange strategy (SES) to yield large-grained perovskite films with high reproducibility. Upon employing a stoichiometric PbI2u2006:u2006MAIu2006:u2006DMSO (3u2006:u20062u2006:u20062) precursor solution, we reduced the number of colloidal intermediates (PbI42−) which is correlated with the nucleation of seeds, resulting in a perovskite thin layer with large grain sizes up to 2 μm. The SES prepared CH3NH3PbI3 devices show significantly reduced grain boundaries corresponding to the decrease of recombination centers, which dramatically boosted the efficiency up to 17.2%.

Sequential deposition method fabricating carbon-based fully-inorganic perovskite solar cells

Hybrid organic-inorganic halide perovskite material has been considered as a potential candidate for various optoelectronic applications. However, their high sensitivity to the environment hampers the actual application. Hence the technology replacing the organic part of the hybrid solar cells needs to be developed. Herein, we fabricated fullyinorganic carbon-based perovskite CsPbBr3 solar cells via a sequential deposition method with a power conversion efficiency of 2.53% and long-time stability over 20 d under ambient air conditions without any encapsulation. An evolution process from tetragonal CsPb2Br5 to CsPb2Br5-CsPbBr3 composites to quasi-cubic CsPbBr3 was found, which was investigated by scanning electron microscopy, X-ray diffraction spectra, UV-vis absorption spectra and Fourier transform infrared spectroscopy. Detailed evolution process was studied to learn more information about the formation process before 10 min. Our results are helpful to the development of inorganic perovskite solar cells and the CsPb2Br5 based optoelectronic devices.摘要有机无机杂化钙钛矿是一种有潜力的光伏材料. 然而, 对于环境的高度敏感性限制了它的实际应用. 因此我们需要发展全无机钙钛矿材料. 本文通过连续沉积法制备了效率达到2.53%的碳电极CsPbBr3太阳电池, 并且它能够在无封装的情况下稳定20天. 在制备CsPbBr3薄膜的过程中, 我们首次发现从CsPb2Br5到CsPb2Br5-CsPbBr3混合物到CsPbBr3的转变. 该研究结果对于无机钙钛矿太阳电池的发展和CsPb2Br5基光电器件具有帮助作用.

Incorporating C60 as Nucleation Sites Optimizing PbI2 Films To Achieve Perovskite Solar Cells Showing Excellent Efficiency and Stability via Vapor-Assisted Deposition Method

To achieve high-quality perovskite solar cells (PSCs), the morphology and carrier transportation of perovskite films need to be optimized. Herein, C60 is employed as nucleation sites in PbI2 precursor solution to optimize the morphology of perovskite films via vapor-assisted deposition process. Accompanying the homogeneous nucleation of PbI2, the incorporation of C60 as heterogeneous nucleation sites can lower the nucleation free energy of PbI2, which facilitates the diffusion and reaction between PbI2 and organic source. Meanwhile, C60 could enhance carrier transportation and reduce charge recombination in the perovskite layer due to its high electron mobility and conductivity. In addition, the grain sizes of perovskite get larger with C60 optimizing, which can reduce the grain boundaries and voids in perovskite and prevent the corrosion because of moisture. As a result, we obtain PSCs with a power conversion efficiency (PCE) of 18.33% and excellent stability. The PCEs of unsealed devices drop less than 10% in a dehumidification cabinet after 100 days and remain at 75% of the initial PCE during exposure to ambient air (humidity > 60% RH, temperature > 30 °C) for 30 days.

Incorporating 4-tert-Butylpyridine in an Antisolvent: A Facile Approach to Obtain Highly Efficient and Stable Perovskite Solar Cells

The synthesis and growth of CH3NH3PbI3 films with controlled nucleation is a key issue for the high efficiency and stability of solar cells. Here, 4-tert-butylpyridine (tBP) was introduced into a CH3NH3PbI3 antisolvent to obtain high quality perovskite layers. In situ optical microscopy and X-ray diffraction patterns were used to prove that tBP significantly suppressed perovskite nucleation by forming an intermediate phase. In addition, a gradient perovskite structure was obtained by this method, which greatly improved the efficiency and stability of perovskites. An effective power conversion efficiency (PCE) of 17.41% was achieved via the tBP treatment, and the high-efficiency device could maintain over 89% of the initial PCE after 30 days at room temperature.

Forming Intermediate Phase on the Surface of PbI2 Precursor Films by Short-Time DMSO Treatment for High-Efficiency Planar Perovskite Solar Cells via Vapor-Assisted Solution Process

Morphology regulation is vital to obtain high-performance perovskite films. Vapor-assisted deposition provides a simple approach to prepare perovskite films with controlled vapor-solid reaction. However, dense PbI2 precursor films with large crystal grains make it difficult for organic molecules to diffuse and interact with inner PbI2 frame. Here, a surface modification process is developed to optimize the surface layer morphology of PbI2 precursor films and lower the resistance of the induced period in crystallization. The vapor optimization time is shortened to several seconds, and the intermediate phase forms on the surface layer of PbI2 films. We achieve porous PbI2 surface with smaller grains through dimethyl sulfoxide vapor treatment, which promotes the migration and reaction rate between CH3NH3I vapor and PbI2 layer. The PbI2 precursor films undergo dramatic morphological evolution due to the formed intermediate phase on PbI2 surface layer. Taking advantage of the proposed surface modification process, we achieve high-quality uniform perovskite films with larger crystal grains and without residual PbI2. The repeatable perovskite solar cells (PSCs) with modified films exhibit power conversion efficiency of up to 18.43% for planar structure. Moreover, the devices show less hysteresis because of improved quality and reduced defect states of the films. Our work expands the application of morphology control through forming intermediate phase and demonstrates an effective way to enhance the performance of the PSCs.

Two-dimensional organic-inorganic hybrid perovskite: from material properties to device applications

The two-dimensional (2D) perovskite (including pure-2D and quasi-2D) is formed by introducing large-group ammonium halides into conventional bulk perovskite. In the past twenty years, 2D perovskite materials were widely developed with the enriched species and advanced physical-knowledge in material characteristics as well as optoelectronic device applications. To review achievments in 2D perovskite, the fundamental mechanism and properties of 2D perovskite are introduced to offer insight into device performance. Moreover, the preparation methods of 2D perovskite films are summarized and compared. The latest successful applications of the 2D perovskite in the solar cells and light-emitting diodes fields, especially the advanced stability of 2D perovskite solar cells (PeSCs) and the efficient 2D perovskite light-emitting diodes (PeLEDs), are also achieved. Furthermore, the challenges and outlook of 2D perovskite materials are proposed.摘要二维(2D)钙钛矿材料(包括纯2D和准2D)是在传统意义上的三维钙钛矿晶格中插入大基团卤化铵形成的. 在过去的20年里, 二维钙钛矿材料种类不断丰富, 相关理论研究不断深入, 在光电器件领域的应用不断拓展. 本综述介绍了2D钙钛矿材料的基本形成机制和性能, 汇总和比较了2D钙钛矿薄膜的制备方法, 并给出了其在太阳电池以及发光二极管领域的应用实例. 最后, 提出了该领域亟待解决的问题, 以及未来的研究趋势.

A star-shaped carbazole-based hole-transporting material with triphenylamine side arms for perovskite solar cells

Herein, we employ a simple star-shaped hole-transporting material (HTM) consisting of a carbazole core and triphenylamine side arms, termed LD29, in mesoscopic perovskite solar cells (PSCs). LD29 exhibits a deep HOMO level of −5.24 eV, a high hole mobility of 1.72 × 10−5 cm2 V−1 s−1, and a relatively high glass-transition temperature of 121 °C, as well as good film-forming ability. PSCs using dopant-free LD29 as the HTM layer exhibit a maximum efficiency of 14.29%. Promisingly, when LD29 is doped, a champion efficiency over 18% has been achieved, which is even comparable with that of the conventional doped spiro-OMeTAD. Moreover, the laboratory synthesis cost for LD29 is significantly lower than that for spiro-OMeTAD. Importantly, the PSC performance does not change greatly with the concentration of LD29 regardless of whether the dopants are used, which has the potential to further reduce material usage. The device employing LD29 also shows comparable stability to that employing spiro-OMeTAD. Consequently, our results provide an important step forward for the commercialized application of PSCs.

Triple cation additive NH3+C2H4NH2+C2H4NH3+-induced phase-stable inorganic α-CsPbI3 perovskite films for use in solar cells

We demonstrate that employing a small quantity of triple cation NH3+C2H4NH2+C2H4NH3+ (denoted as DETA3+) could effectively stabilize mutable α-CsPbI3 for 60 d via a facile one-step deposition method without any encapsulation. Reasons for the remarkable improvement of phase-stability for CsPbI3 are generalized into three aspects: (1) the reduction of CsPbI3 crystalline grains, (2) avoiding spontaneous octahedral tilting caused by ionic bonds between NH3+ or RNH2+ groups of DETA3+ and I− of [PbI6]4− in CsPbI3 perovskite crystals formed on the surface or grain boundaries of the CsPbI3 and (3) enhancement of the hydrophobicity of inorganic perovskite layers induced by the oil-wet (hydrophobic) hydrocarbon chains of DETA3+ aggregated on the surfaces. Excellent photovoltaic properties of the CsPbI3·xDETAI3 perovskite films with reduced nonradiative recombination are achieved. The best solar cell with the configuration of FTO/compact-TiO2/CsPbI3·xDETAI3/P3HT/Au shows a power conversion efficiency (PCE) of 7.89% and retains 92% of its initial PCE after storage for 1008 h in a dark dry box without any encapsulation.

An ultrathin SiO2 blocking layer to suppress interfacial recombination for efficient Sb2S3-sensitized solar cells

Interfacial charge recombination is a serious problem in semiconductor-sensitized solar cells which severely limits the power conversion efficiency. Herein, an ultrathin SiO2 blocking layer was introduced to the TiO2 surface to suppress the interfacial recombination in Sb2S3-sensitized solar cells. The SiO2 blocking layer was deposited by a simple chemical bath method. Due to the unique features of the SiO2 layer, the Sb2S3 sensitizer shows a remarkable change in the morphology after SiO2 coating, forming numerous irregular large crystals which did not bring a negative impact. Electrochemical impedance spectra and open-circuit voltage-decay analysis confirm that the SiO2 layer efficiently suppresses the interfacial recombination at the TiO2/Sb2S3 interface which is the major recombination path in the solar cells. As a result, the device exhibits remarkably enhanced open-circuit voltage, fill factor and power conversion efficiency.