Not All That Glitters Is Gold: Metal-Migration-Induced Degradation in Perovskite Solar Cells (original) (raw)
Related papers
ACS Energy Letters, 2018
Metal-contact-induced degradation and escape of volatile species from perovskite solar cells necessitate excellent diffusion barrier layers. We show that metal-induced degradation limits thermal stability in several perovskite chemistries with Au, Cu, and Ag gridlines even when the metal is separated from the perovskite by a layer of indium tin oxide (ITO). Channels in a sputtered ITO layer that align with perovskite grain boundaries are pathways for metal and halide diffusion into or out of the perovskite. Planarizing the perovskite morphology with a spin-cast organic chargetransport layer results in a subsequently deposited ITO layer that is uniform and impermeable. We show that it is critical to seal the edges of the active layers to prevent escape of volatile species. We demonstrate 1000 h thermal stability at 85°C in CH 3 NH 3 PbI 3 solar cells with complete-coverage silver contacts. Our barrier layer design enables long-term thermal stability of perovskite solar cells, a critical step to commercialization.
Understanding the Degradation of Spiro‐OMeTAD‐Based Perovskite Solar Cells at High Temperature
Solar RRL
Organic-inorganic halide perovskites are promising as the light absorber of solar cells because of their efficient solar power conversion. An issue frequently occurring in perovskite solar cells (PSCs) with a hole transport layer of N,N-di(4-methoxyphenyl)amino]-9,9'-spirobifluorene (spiro-OMeTAD) is a quick performance degradation at high temperature. In this study, we discover that post-doping of the spiro-OMeTAD layer by iodine released from the perovskite layer is one possible mechanism of the high-temperature PSC degradation. The iodine doping leads to the highest occupied molecular orbital level of the spiro-OMeTAD layer becoming deeper and, therefore, induces the formation of an energy barrier for hole extraction from the perovskite layer. We demonstrate that it is possible to suppress the high-temperature degradation by employing an iodine-blocking layer or an iodine-free perovskite in PSCs. These findings will guide the way for the realization of thermally stable perovskite optoelectronic devices in the future. 1. Introduction Metal halide perovskites are promising as the light absorber of solar cells. Power conversion efficiencies (PCEs) of perovskite solar cells (PSCs) have already reached a very high level of up to 25.2 %, [1] which is comparable to silicon solar cell technology. Such high PCEs derive from suitable bandgaps, high absorption coefficients, high carrier mobilities, and long carrier diffusion lengths. [2-6] Compatibility with simple solution processing [7] is an additional advantage which makes the fabrication cost of PSCs lower. In sharp contrast to the high PCEs, the long-term operational stability of PSCs is still problematic. For example, the PSC degradation proceeds in the presence of light, moisture, or oxygen. [8-19] Additionally, it is known that the PSC performance more quickly decreases at high temperature than at room temperature. [20,21] For future commercialization, it is necessary to ensure the high-temperature stability of PSCs. On the basis of 2010 International Summit on Organic PV Stability (ISOS) protocol (Roskilde, Denmark), [22] solar cells need to work properly even at high temperatures ranging from 65 to 85 °C. Author efficiencies (PCEs) of perovskite solar cells (PSCs) have already reached a very high level of up to Author efficiencies (PCEs) of perovskite solar cells (PSCs) have already reached a very high level of up to Author which is comparable to silicon solar cell technology. Author which is comparable to silicon solar cell technology. suitable bandgaps, high absorption coefficients, high carrier mobilities, and long carrier diffusion Author suitable bandgaps, high absorption coefficients, high carrier mobilities, and long carrier diffusion Compatibility
Perovskite solar cells: The new epoch in photovoltaics
Solar Energy, 2020
Perovskite-based solar cells (PSC) is the fastest growing solar technology to date since inception in 2009. This technology has revolutionized the photovoltaic (PV) community. While it has taken 15-42 years for traditional PV technologies to achieve maturity, PSC technology has accomplished the same within 10 years. In this article, we explore the latest developments in respect of material profile, pathways for crystallization and device architectures. Related to this are lifetime and stability which are detected as the vital issues that need to be solved before the PSC technology can be commercialized on a wider scale. In addition, we critically elucidate the key degradation mechanisms and strategies for improvement of stability. The fact that most of the perovskite elements are not optimized suggests that there's still room for enhancement-especially in relation to the hole transport materials (HTMs) used and the organic component of the perovskite materials. Lastly, we discuss future outlook and necessary updates for PV community.
Progress in hole-transporting materials for perovskite solar cells
Journal of Energy Chemistry, 2018
In recent years the photovoltaic community has witnessed the unprecedented development of perovskite solar cells (PSCs) as they have taken the lead in emergent photovoltaic technologies. The power conversion efficiency of this new class of solar cells has been increased to a point where they are beginning to compete with more established technologies. Although PSCs have evolved a variety of structures, the use of hole-transporting materials (HTMs) remains indispensable. Here, an overview of the various types of available HTMs is presented. This includes organic and inorganic HTMs and is presented alongside recent progress in associated aspects of PSCs, including device architectures and fabrication techniques to produce high-quality perovskite films. The structure, electrochemistry, and physical properties of a variety of HTMs are discussed, highlighting considerations for those designing new HTMs. Finally, an outlook is presented to provide more concrete direction for the development and optimization of HTMs for highefficiency PSCs.
Perovskite solar cells: In pursuit of efficiency and stability
Materials & Design, 2017
Perovskite solar cells (PSCs) are coming with positive hopes for researchers to commercialize high-power conversion efficiency (PCE) and low-cost solar cells. Recently, NREL-certified record PCE of PSC is 22.1 %, which is competing to silicon solar cells has been reported. However, PSC devices are environmentally sensitive leading to a rapid PCE degradation. Therefore, it is important to understand the impact of the role of various parameters to achieve highly stable PSC without compromising on its performance. This review contains an overview of a recent progress in PSC with respect to PCE, materials engineering, and stability. Energy level diagram of various perovskite materials, electron conducting materials (ECMs) and hole conducting materials (HCMs) constitute pivotal role in selecting their combinations. Hence we have added detailed energy level diagrams from which researcher can select best possible combination to achieve highest efficiency. An indepth discussion on the types of PSCs based on thin film, mesoporous, n-i-p and p-in architectures fabricated by using different deposition techniques has been provided. In order to transfer this exciting achievement to industry level, it is necessary to understand degradation process at different conditions. A detailed discussion on the mechanism of recombination, instability in PSCs and achieved success has been incorporated to apprehend the step-wise developments in this field and to find possible pathways that limit their stability.
Sustainable Materials and Technologies, 2020
This is a PDF file of an article that has undergone enhancements after acceptance, such as the addition of a cover page and metadata, and formatting for readability, but it is not yet the definitive version of record. This version will undergo additional copyediting, typesetting and review before it is published in its final form, but we are providing this version to give early visibility of the article. Please note that, during the production process, errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.
Recent progress concerning inorganic hole transport layers for efficient perovskite solar cells
Journal, 2019
Typically, low cost as well as stability factors of the organo-metal halide perovskite solar cells based on inorganic hole transport layers (HTLs) have been the focus of intense research over the past few years. Accordingly, the power conversion efficiencies have rapidly been improved to ~ 20% with high stabilities. Therefore, this review covers the major advances of inorganic HTLs in perovskite solar cells that have contributed to the recent efficiencies and stabilities, including the evolution of device architecture, the development of hole transport material deposition processes, synthesis, morphology and the interface properties between inorganic HTLs and perovskite layers. Eventually, the challenges and future directions for inorganic HTLs-based perovskite solar cells are also discussed.
Iodine Migration and Degradation of Perovskite Solar Cells Enhanced by Metallic Electrodes
The Journal of Physical Chemistry Letters, 2016
We monitored the evolution in time of pinhole-free structures based on FTO/TiO 2 /CH 3 NH 3 PbI 2.6 Cl 0.4 layers, with and without spiro-OMeTAD and counter electrodes (Ag, Mo/Ag and Au), aged at 24 0 C in dark and nitrogen atmosphere. In the absence of electrodes no degradation occurs. While devices with Au show only a 10% drop in power conversion efficiency, remaining stable after a further overheating at 70 0 C, more than 90% is lost when using Ag, the process being slower for Mo/Ag. We demonstrate that iodine is dislocated by the electric field between the electrodes and this is an intrinsic cause for electro-migration of Ifrom the perovskite until reaching the anode. The iodine exhaustion in the perovskite layer is produced when using Ag electrodes and AgI is formed. We hypothesize that in the presence of Au the iodine migration is limited due to the built-up of Inegative space charge accumulated at the perovskite-OMeTAD interface.
Electronics
Perovskite solar cells (PSCs) have revolutionized the field of photovoltaics, achieving certified power conversion efficiencies reaching 26% at the laboratory scale. High performance, enhanced stability, and long lifetime are prerequisites for the industrialization and commercialization of this class of third-generation photovoltaic technology. Toward the development of well-performing and robust PSCs against environmental stresses, advanced engineering strategies have been employed, targeting the preparation of perovskite absorbing layers with minimal defects and energy-level fine-tuning hydrophobic contacts. Focusing on both the electron transport layer/perovskite and perovskite/hole transport layer interfaces, this review work encompasses some of the most promising engineering methodologies that were recently proposed in order to optimize the device architecture. Machine learning approaches have also been used to validate experimental data and predict with accuracy solar cell par...