Biao Shi

Elucidating the role of chlorine in perovskite solar cells

It has been proposed that introducing the chlorine anion into a CH3NH3PbI3 perovskite material can substantially improve the materials properties as well as the solar cell performance. To elucidate the role of chlorine in perovskite solar cells (PSCs), here we introduced PbCl2 into the precursor, and studied the chlorine configuration evolution during perovskite film formation and the associated influence on PSC performance in detail. We found that chlorine could be successfully incorporated into the precursor film in the form of PbICl or PbCl2 through a properly designed preparation, and it was conserved in the final perovskite film with a configuration of MAPbCl3, PbICl or PbCl2 depending on the fabrication process. However, no evidence of a MAPbI3−xClx phase was observed, and it is considered that MAPbI3−xClx might be metastable or possesses a higher formation energy. In addition, we demonstrate that the formation of a porous PbICl scaffold in the precursor film plays a key role in high quality perovskite film realization, benefiting from an effective stress release during structure expansion after methylammonium iodide dripping. Moreover, we propose that residual amorphous PbCl2 can effectively passivate defects in perovskite film, and dramatically improve the film’s electrical properties. Finally, n–i–p type planar PSCs with efficiencies up to 19.45% were achieved. It should be mentioned that the whole process for the formation of the PSCs is performed at less than 100 °C, which is beneficial for a wide range of applications, such as flexible and tandem solar cells.

Hydrogenated TiO2 Thin Film for Accelerating Electron Transport in Highly Efficient Planar Perovskite Solar Cells

Abstract Intensive studies on low‐temperature deposited electron transport materials have been performed to improve the efficiency of n‐i‐p type planar perovskite solar cells to extend their application on plastic and multijunction device architectures. Here, a TiO2 film with enhanced conductivity and tailored band edge is prepared by magnetron sputtering at room temperature by hydrogen doping (HTO), which accelerates the electron extraction from perovskite photoabsorber and reduces charge transfer resistance, resulting in an improved short circuit current density and fill factor. The HTO film with upward shifted Fermi level guarantees a smaller loss on V OC and facilitates the growth of high‐quality absorber with much larger grains and more uniform size, leading to devices with negligible hysteresis. In comparison with the pristine TiO2 prepared without hydrogen doping, the HTO‐based device exhibits a substantial performance enhancement leading to an efficiency of 19.30% and more stabilized photovoltaic performance maintaining 93% of its initial value after 300 min continuous illumination in the glove box. These properties permit the room‐temperature magnetron sputtered HTO film as a promising electron transport material for flexible and tandem perovskite solar cell in the future.

Electron transport layer driven to improve the open-circuit voltage of CH3NH3PbI3 planar perovskite solar cells

Suitable electron transport layers are essential for high performance planar perovskite heterojunction solar cells. Here, we use ZnO electron transport layer sputtered under oxygen-rich atmosphere at room temperature to decrease the hydroxide and then suppress decomposition of perovskite films. The perovskite films with improved crystallinity and morphology are achieved. Besides, on the ZnO substrate fabricated at oxygen-rich atmosphere, open-circuit voltage of the CH3NH3PbI3-based perovskite solar cells increased by 0.13 V. A high open-circuit voltage of 1.16 V provides a good prospect for the perovskite-based tandem solar cells. The ZnO sputtered at room temperature can be easily fabricated industrially on a large scale, therefore, compatible to flexible and tandem devices. Those properties make the sputtered ZnO films promising as electron transport materials for perovskite solar cells.摘要电子传输层对于N-I-P型平面钙钛矿太阳电池的性能至关重要. ZnO薄膜由于其高载流子迁移率在钙钛矿太阳电池中被广泛应用,但是薄膜内部羟基的存在影响了电池性能. 本文在磁控溅射沉积ZnO薄膜的过程中引入富氧环境来抑制ZnO中羟基的生成, 进而抑制钙钛矿薄膜的分解, 从而获得具有较高结晶质量的均匀致密的钙钛矿薄膜. 基于富氧环境下制备的ZnO作为电子传输层的钙钛矿太阳电池开压增加了0.13 V. 1.16 V的高开路电压对钙钛矿太阳电池在叠层电池中的应用提供了较好的发展前景. 此外, 室温磁控溅射制备的ZnO可以实现大面积工业化生产, 且适用于柔性和叠层器件. 该研究表明ZnO在太阳电池领域具有潜在应用.

Novel Insight into the Function of PC 61 BM in Efficient Planar Perovskite Solar Cells

We introduced a PC61BM layer between the compact TiO2 layer and the perovskite absorber, which forms a porous precursor film, and thus promotes uniform perovskite films with large grain size and improves the device efficiency.