Ying-Ke Ren

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 PbI2 : MAI : DMSO (3 : 2 : 2) 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.

Identification and characterization of a new intermediate to obtain high quality perovskite films with hydrogen halides as additives

High quality perovskite films were fabricated from different precursor solutions containing a certain proportion of different hydrogen halides. An anti-solvent, toluene, was used here to isolate an intermediate from the perovskite precursor solution to reveal the impact of the hydrogen halides on the crystallization of perovskite films. From the Fourier transform infrared spectra we found that the stretch vibration of CO for pure N,N-dimethylformamide (DMF) appeared at 1663 cm−1, which was shifted to a smaller wavenumber while reacting DMF with CH3NH3I (MAI) + PbI2 and MAI + PbI2 + HX (X = Cl, Br, I). Moreover, the appearance of X-ray diffraction (XRD) peaks at low angles (near 8 degrees) as well as some small angle shift showed that the MAI–PbI2–DMF–xHX (X = Cl, Br, I) intermediate was formed, which benefits perovskite crystallization because the formation of the intermediate will avoid a rapid reaction between MAI and PbI2. Whats more, the solubility of the precursor can be improved by adding hydrogen halides. By adding a certain amount of hydrogen halide into the one-step perovskite precursor solution we can obtain pin-hole free and almost no defect films. Transient absorption (TA) was carried out to investigate the charge recombination in intrinsic perovskite films and perovskite devices, giving some reasonable interpretations.

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.

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.