Perovskite solar cells (PSCs) with efficiencies greater than 20% have been realized only with expensive organic hole-transporting materials. We demonstrate PSCs that achieve stabilized efficiencies exceeding 20% with copper(I) thiocyanate (CuSCN) as the hole extraction layer. A fast solvent removal method enabled the creation of compact, highly conformal CuSCN layers that facilitate rapid carrier extraction and collection. The PSCs showed high thermal stability under long-term heating, although their operational stability was poor. This instability originated from potential-induced degradation of the CuSCN/Au contact. The addition of a conductive reduced graphene oxide spacer layer between CuSCN and gold allowed PSCs to retain >95% of their initial efficiency after aging at a maximum power point for 1000 hours under full solar intensity at 60°C. Under both continuous full-sun illumination and thermal stress, CuSCN-based devices surpassed the stability of spiro-OMeTAD–based PSCs.

https://science.sciencemag.org/content/sci/early/2017/09/27/science.aam5655.full.pdf

Perovskite solar cells with CuSCN hole extraction layers yield stabilized efficiencies greater than 20

2,2′,7,7′-tetrakis-(N,N-di-4-methoxyphenylamino)-9,9′-spirobifluorene (spiro-MeOTAD) hole transport material (HTM) is a milestone in the history of perovskite solar cells (PSCs). Proper choice of HTMs is key factor for efficient charge extraction and stability in solar cells. Spiro-MeOTAD is proven to be the most suitable HTM for testing PSCs due to its facile implementation and high performance. Similarly, spiro-MeOTAD is receiving attention in other applications other than in solar cells due to its desirable properties. However, spiro-MeOTAD is under debate regarding the topics of cost-performance, long-term stability, degradation issues (induced by temperature, additives, film quality, and environmental conditions), coating technologies compatibility, reliance on additives, and hysteresis. In this review, the advent of spiro-MeOTAD, and related aforementioned issues about spiro-MeOTAD are discussed. In addition, spiro-MeOTAD properties, alternative and new additives, other applications, and new HTMs that is comparable or outperforms spiro-MeOTAD in PSCs are summarized. In the outlook, the future research directions based on reported results that warrant further investigations are outlined.

https://onlinelibrary.wiley.com/doi/pdf/10.1002/admi.201700623

Recent Advances in Spiro-MeOTAD Hole Transport Material and Its Applications in Organic–Inorganic Halide Perovskite Solar Cells

Simultaneous Improvement of Photovoltaic Performance and Stability by In Situ Formation of 2D Perovskite at (FAPbI3)0.88(CsPbBr3)0.12/CuSCN Interface

With the rapid increase of efficiency up to 22.1% during the past few years, hybrid organic-inorganic metal halide perovskite solar cells (PSCs) have become a research “hot spot” for many solar cell researchers. The perovskite materials show various advantages such as long carrier diffusion lengths, widely-tunable band gap with great light absorption potential. The low-cost fabrication techniques together with the high efficiency makes PSCs comparable with Si-based solar cells. But the drawbacks such as device instability, J-V hysteresis and lead toxicity reduce the further improvement and the future commercialization of PSCs. This review begins with the discussion of crystal and electronic structures of perovskite based on recent research findings. An evolution of PSCs is also analyzed with a greater detail of each component, device structures, major device fabrication methods and the performance of PSCs acquired by each method. The following part of this review is the discussion of major barriers on the pathway for the commercialization of PSCs. The effects of crystal structure, fabrication temperature, moisture, oxygen and UV towards the stability of PSCs are discussed. The stability of other components in the PSCs are also discussed. The lead toxicity and updated research progress on lead replacement are reviewed to understand the sustainability issues of PSCs. The origin of J-V hysteresis is also briefly discussed. Finally, this review provides a roadmap on the current needs and future research directions to address the main issues of PSCs.

Perovskites-Based Solar Cells: A Review of Recent Progress, Materials and Processing Methods

Hole Transport Materials in Conventional Structural (n–i–p) Perovskite Solar Cells: From Past to the Future

In this Letter we show that the mixed perovskite in the form of (FAPbI3)0.85(MAPbBr3)0.15 in combination with CuNCS as p-type hole conductor leads to over 16% power conversion efficiency (PCE) under full sun illumination and yields a remarkable monochromatic incident photon-to-electron conversion efficiency of 85%. The devices displayed a short-circuit current density (Jsc) of 21.8 mA/cm2, open-circuit voltage (Voc) of 1100 mV, fill factor (FF) of 0.69, and a PCE of 16.6%. Under similar conditions, the device without CuSCN shows a PCE of 9.5%, with a significant decrease in the Jsc (from 21.8 mA/cm2 to 15.64 mA/cm2) and Voc (from 1100 mV to 900 mV). The high Jsc with CuSCN is mainly due to the effective charge transfer between perovskite and CuSCN, followed by the fast hole transport through CuSCN to the Au. In comparison, the spiro-OMeTAD reference cells showed efficiencies up to 19.65%. Different from most organic hole-transporting materials is the transparency and high hole mobility of CuSCN, which rep...

Copper Thiocyanate Inorganic Hole-Transporting Material for High-Efficiency Perovskite Solar Cells

Chalcogenide Materials and Derivatives for Photovoltaic Applications

Soiling of photovoltaic panels in the Gulf Cooperation Council countries and mitigation strategies

Controlling the porosity, the shape, and the morphology of Kirkendall hollow nanostructures is the key factor to tune the properties of these tailor-made nanomaterials which allow in turn broadening their applications. It is shown that by applying a continuous oxidation to copper nanowires following a temperature ramp protocol, one can synthesize cuprous oxide nanotubes containing periodic copper nanoparticles. A further oxidation of such nanoobjects allows obtaining cupric oxide nanotubes with a bamboo-like structure. On the other hand, by applying a sequential oxidation and reduction reactions to copper nanowires, one can synthesize hollow nanoobjects with complex shapes and morphologies that cannot be obtained using the Kirkendall effect alone, such as necklace-like cuprous oxide nanotubes, periodic solid copper nanoparticles or hollow cuprous oxide nanospheres interconnected with single crystal cuprous oxide nanorods, and aligned and periodic hollow nanospheres embedded in a cuprous oxide nanotube. The strategy demonstrated in this study opens new avenues for the engineering of hollow nanostructures with potential applications in gas sensing, catalysis, and energy storage.

Controlling the Formation of Nanocavities in Kirkendall Nanoobjects through Sequential Thermal Ex Situ Oxidation and in Situ Reduction Reactions

Drop-on-demand inkjet printing is an easily up-scalable, rapid and digital deposition technique that allows thin film formation with a high material utilization rate as ideally needed for solar cells production In this contribution, a method is reported to prepare inkjet-printed compact TiO2 thin films that are further assessed as electron transport layer (ETL) for perovskite solar cells and compared to reference dip-coated TiO2 layers Through ink formula engineering and adjustment of the printing parameters, a reliable process control is achieved leading to a homogeneous TiO2 coating of the FTO substrate Perovskite solar cells with inkjet-printed TiO2 ETL yielded efficiencies up to 13 7?%, outperforming the efficiency and the process repeatability of devices prepared with our dip coated TiO2 reference Together with other recent contributions on inkjet-printed perovskite solar cells, this work contributes to highlight the processability of thin film solar cells using digital inkjet printing for next generation photovoltaic applications This article is protected by copyright All rights reserved

Marie Buffiere

Papers

Copper Thiocyanate Inorganic Hole-Transporting Material for High-Efficiency Perovskite Solar Cells

Chalcogenide Materials and Derivatives for Photovoltaic Applications

Soiling of photovoltaic panels in the Gulf Cooperation Council countries and mitigation strategies

Controlling the Formation of Nanocavities in Kirkendall Nanoobjects through Sequential Thermal Ex Situ Oxidation and in Situ Reduction Reactions

Inkjet‐Printed Compact TiO2 Electron Transport Layer for Perovskite Solar Cells