Perovskite Solar Cells on Corrugated Substrates with Enhanced Efficiency

Organometallic halide perovskites solar cells are fabricated on nano‐scaled corrugated substrates using a sequential deposition method. The corrugated substrates are fabricated using colloidal lithography followed by reactive ion etching. The corrugated structure is found to accelerate the chemical reaction between the sequentially deposited lead iodide (PbI₂) and methyl ammonium iodide layers to form stoichiometric perovskite films, and the corrugated morphology is preserved at the interface of the hole transport layer (HTL) and the perovskite layer. The shunt resistance of the corrugated devices is found to be higher than that of the planar devices, leading to a higher open circuit voltage (V_OC) and fill factor (FF) in the corrugated devices. Finite‐difference time‐domain simulation is carried out on both planar and corrugated devices. The results revealed that light absorption is enhanced in the corrugated devices due to the corrugated HTL/perovskite interface, resulting in a significantly higher short circuit current (J_SC) observed in the corrugated devices. As a result, the average power conversion efficiency increases from 8.7% for the planar devices to 13% for the corrugated devices.     

Dual Defect-Passivation Using Phthalocyanine for Enhanced Efficiency and Stability of Perovskite Solar Cells

Semiconducting molecules have been employed to passivate traps extant in the perovskite film for enhancement of perovskite solar cells (PSCs) efficiency and stability. A molecular design strategy to passivate the defects both on the surface and interior of the CH₃NH₃PbI₃ perovskite layer, using two phthalocyanine (Pc) molecules (NP-SC₆-ZnPc and NP-SC₆-TiOPc) is demonstrated. The presence of lone electron pairs on S, N, and O atoms of the Pc molecular structures provides the opportunity for Lewis acid–base interactions with under-coordinated Pb²⁺ sites, leading to efficient defect passivation of the perovskite layer. The tendency of both NP-SC₆-ZnPc and NP-SC₆-TiOPc to relax on the PbI₂ terminated surface of the perovskite layer is also studied using density functional theory (DFT) calculations. The morphology of the perovskite layer is improved due to employing the Pc passivation strategy, resulting in high-quality thin films with a dense and compact structure and lower surface roughness. Using NP-SC₆-ZnPc and NP-SC₆-TiOPc as passivating agents, it is observed considerably enhanced power conversion efficiencies (PCEs), from 17.67% for the PSCs based on the pristine perovskite film to 19.39% for NP-SC₆-TiOPc passivated devices. Moreover, PSCs fabricated based on the Pc passivation method present a remarkable stability under conditions of high moisture and temperature levels.     

Gradient Energy Alignment Engineering for Planar Perovskite Solar Cells with Efficiency Over 23%

An electron-transport layer (ETL) with appropriate energy alignment and enhanced charge transfer is critical for perovskite solar cells (PSCs). However, interfacial energy level mismatch limits the electrical performance of PSCs, particularly the open-circuit voltage (V_OC). Herein, a simple low-temperature-processed In₂O₃/SnO₂ bilayer ETL is developed and used for fabricating a new PSC device. The presence of In₂O₃ results in uniform, compact, and low-trap-density perovskite films. Moreover, the conduction band of In₂O₃ is shallower than that of Sn-doped In₂O₃ (ITO), enhancing the charge transfer from perovskite to ETL, thus minimizing V_OC loss at the perovskite and ETL interface. A planar PSC with a power conversion efficiency of 23.24% (certified efficiency of 22.54%) is obtained. A high V_OC of 1.17 V is achieved with the potential loss at only 0.36 V. In contrast, devices based on single SnO₂ layers achieve 21.42% efficiency with a V_OC of 1.13 V. In addition, the new device maintains 97.5% initial efficiency after 80 d in N₂ without encapsulation and retains 91% of its initial efficiency after 180 h under 1 sun continuous illumination. The results demonstrate and pave the way for the development of efficient photovoltaic devices.     

Tailored Amphiphilic Molecular Mitigators for Stable Perovskite Solar Cells with 23.5% Efficiency

Passivation of interfacial defects serves as an effective means to realize highly efficient and stable perovskite solar cells (PSCs). However, most molecular modulators currently used to mitigate such defects form poorly conductive aggregates at the perovskite interface with the charge collection layer, impeding the extraction of photogenerated charge carriers. Here, a judiciously engineered passivator, 4-tert-butyl-benzylammonium iodide (tBBAI), is introduced, whose bulky tert-butyl groups prevent the unwanted aggregation by steric repulsion. It is found that simple surface treatment with tBBAI significantly accelerates the charge extraction from the perovskite into the spiro-OMeTAD hole-transporter, while retarding the nonradiative charge carrier recombination. This boosts the power conversion efficiency (PCE) of the PSC from ≈20% to 23.5% reducing the hysteresis to barely detectable levels. Importantly, the tBBAI treatment raises the fill factor from 0.75 to the very high value of 0.82, which concurs with a decrease in the ideality factor from 1.72 to 1.34, confirming the suppression of radiation-less carrier recombination. The tert-butyl group also provides a hydrophobic umbrella protecting the perovskite film from attack by ambient moisture. As a result, the PSCs show excellent operational stability retaining over 95% of their initial PCE after 500 h full-sun illumination under maximum-power-point tracking under continuous simulated solar irradiation.     

Integrated Perovskite/Bulk-Heterojunction Organic Solar Cells

The recently emerged integrated perovskite/bulk-heterojunction (BHJ) organic solar cells (IPOSCs) without any recombination layers have generated wide attention. This type of device structure can take the advantages of tandem cells using both perovskite solar and near-infrared (NIR) BHJ organic solar materials for wide-range sunlight absorption and the simple fabrication of single junction cells, as the low bandgap BHJ layer can provide additional light harvesting in the NIR region and the high open-circuit voltage can be maintained at the same time. This progress report highlights the recent developments in such IPOSCs and the possible challenges ahead. In addition, the recent development of perovskite solar cells and NIR organic solar cells is also covered to fully underline the importance and potential of IPOSCs.     

Reliable Measurement of Perovskite Solar Cells

Perovskite solar cells (PSCs) have undergone an incredibly fast development and attracted intense attention worldwide owing to their high efficiency and low‐cost fabrication. However, it is challenging to make a reliable measurement of PSCs, which creates great difficulty for researchers to compare and reproduce published results. Herein, the major measurement methods and key factors affecting evaluation of PSCs are summarized, such as hysteresis in current–voltage measurement, calibration of solar simulators for less mismatch in spectra and light intensity, and the area for the calculation of current density and power conversion efficiency. PSCs are also compared with n–i–p or p–i–n structures that exhibit different feedback under the same measurement methods. Finally, a measurement proposal is provided to help researchers obtain reliable measurement results close to those certified by public test centers.     

钙钛矿太阳能电池:从高效率到稳定性

钙钛矿太阳能电池(Perovskite solar cells,PSCs)由于制备工艺简单、价格便宜、转换效率高、可制备柔性器件等优点引起广泛关注。近年来,钙钛矿太阳能电池的转换效率不断被刷新,迅速实现了对多晶硅太阳能电池的超越,使其具有巨大的商业潜力。然而,稳定性成为阻碍钙钛矿太阳能电池商业化的一大问题。介绍了钙钛矿太阳能电池的结构,综述了钙钛矿太阳能电池所取得的研究进展,总结了获得高效率钙钛矿太阳能电池的方法,重点分析了提高钙钛矿太阳能电池稳定性的策略,并指出钙钛矿太阳能电池的发展方向。     

Quasi‐Heteroface Perovskite Solar Cells

Perovskite solar cells (PSCs) have attracted unprecedented attention due to their rapidly rising photoelectric conversion efficiency (PCE). In order to further improve the PCE of PSCs, new possible optimization path needs to be found. Here, quasi‐heteroface PSCs (QHF‐PSCs) is designed by a double‐layer perovskite film. Such brand new PSCs have good carrier separation capabilities, effectively suppress the nonradiative recombination of the PSCs, and thus greatly improve the open‐circuit voltage and PCE. The root cause of the performance improvement is the benefit from the additional built‐in electric field, which is confirmed by measuring the external quantum efficiency under applied electric field and Kelvin probe force microscope. Meanwhile, an intermediate band gap perovskite layer can be obtained simply by combining a wide band gap perovskite layer with a narrow band gap perovskite layer. Tunability of the band gap is obtained by varying the film thicknesses of the narrow and wide band gap layers. This phenomenon is quite different from traditional inorganic solar cells, whose band gap is determined only by the narrowest band gap layer. It is believed that these QHF‐PSCs will be an effective strategy to further enhance PCE in PSCs and provide basis to further understand and develop the perovskite materials platform.     

Planar‐Structure Perovskite Solar Cells with Efficiency beyond 21%

Low temperature solution processed planar‐structure perovskite solar cells gain great attention recently, while their power conversions are still lower than that of high temperature mesoporous counterpart. Previous reports are mainly focused on perovskite morphology control and interface engineering to improve performance. Here, this study systematically investigates the effect of precise stoichiometry, especially the PbI₂ contents on device performance including efficiency, hysteresis and stability. This study finds that a moderate residual of PbI₂ can deliver stable and high efficiency of solar cells without hysteresis, while too much residual PbI₂ will lead to serious hysteresis and poor transit stability. Solar cells with the efficiencies of 21.6% in small size (0.0737 cm²) and 20.1% in large size (1 cm²) with moderate residual PbI₂ in perovskite layer are obtained. The certificated efficiency for small size shows the efficiency of 20.9%, which is the highest efficiency ever recorded in planar‐structure perovskite solar cells, showing the planar‐structure perovskite solar cells are very promising.     

钙钛矿太阳能电池技术发展历史与现状

简要回顾了钙钛矿太阳能电池的发展历史,解释了钙钛矿太阳能电池本质上是固态染料敏化太阳能电池。介绍了钙钛矿太阳能电池的微观发电机理,结合钙钛矿太阳能电池的能级图分析讨论了钙钛矿与电子传输层和空穴传输层的能级匹配。分析总结了钙钛矿太阳能电池的光伏技术参数,包括光生电流密度、开路电压、填充因子、能量转换效率以及光伏性能的稳定性。钙钛矿太阳能电池的能量转换效率、短路电流密度和开路电压均已超过非晶硅薄膜太阳能电池,填充因子与非晶硅薄膜太阳能电池很接近。钙钛矿太阳能电池有希望实现产业化而成为下一代薄膜太阳能电池。指出了钙钛矿太阳能电池大规模市场应用在制造技术上的瓶颈即空穴传输层的造价昂贵,并综述了解决该瓶颈的最新研究工作。     

Historical Analysis of High-Efficiency,Large-Area Solar Cells: Toward Upscaling of Perovskite Solar Cells

The status and problems of upscaling research on perovskite solar cells, which must be addressed for commercialization efforts to be successful, are investigated. An 804 cm² perovskite solar module has been reported with 17.9% efficiency, which is significantly lower than the champion perovskite solar cell efficiency of 25.2% reported for a 0.09 cm² aperture area. For the realization of upscaling high-quality perovskite solar cells, the upscaling and development history of conventional silicon, copper indium gallium sulfur/selenide and CdTe solar cells, which are already commercialized with modules of sizes up to ≈25 000 cm², are reviewed. GaAs, organic, dye-sensitized solar cells and perovskite/silicon tandem solar cells are also reviewed. The similarities of the operating mechanisms between the various solar cells and the origin of different development pathway are investigated, and the ideal upscaling direction of perovskite solar cells is subsequently proposed. It is believed that lessons learned from the historical analysis of various solar cells provide a fundamental diagnosis of relative and absolute development status of perovskite solar cells. The unique perspective proposed here can pave the way toward the upscaling of perovskite solar cells.     

Self-Repairing Tin-Based Perovskite Solar Cells with a Breakthrough Efficiency Over 11%

The development of tin (Sn)-based perovskite solar cells (PSCs) is hindered by their lower power conversion efficiency and poorer stability compared to the lead-based ones, which arise from the easy oxidation of Sn²⁺ to Sn⁴⁺. Herein, phenylhydrazine hydrochloride (PHCl) is introduced into FASnI₃ (FA = NH₂CH  NH₂⁺) perovskite films to reduce the existing Sn⁴⁺ and prevent the further degradation of FASnI₃, since PHCl has a reductive hydrazino group and a hydrophobic phenyl group. Consequently, the device achieves a record power conversion efficiency of 11.4% for lead-free PSCs. Besides, the unencapsulated device displays almost no efficiency reduction in a glove box over 110 days and shows efficiency recovery after being exposed to air, due to a proposed self-repairing trap state passivation process.     

钙钛矿太阳能电池的研究进展

作为一种新型清洁可再生能源,钙钛矿太阳能电池(Perovskite solar cells,PSC)从发展至今已取得了重大的突破,成为研究的热点。主要介绍了钙钛矿太阳能电池的基本结构和工作原理及电子传输层、钙钛矿层、空穴传输层的制备方法,以及在发展过程中所面临的技术问题,最后展望了钙钛矿太阳能电池未来的研究重点及发展前景。