Recent Progresses on Defect Passivation toward Efficient Perovskite Solar Cells

Additive Engineering for Efficient and Stable Perovskite Solar Cells

Recently, perovskite solar cells (PSCs) have attracted much attention owing to their high power conversion efficiency (25.2%) and low fabrication cost. However, the short lifetime under operation is the major obstacle for their commercialization. With efforts from the entire PSC research community, significant advances have been witnessed to improve the device operational stability, and a timely summary on the progress is urgently needed. In this review, we first clarify the definition of operational stability and its significance in the context of practical use. By analyzing the mechanisms in established approaches for operational stability improvement, we summarize several effective strategies to extend device lifetime in a layer-by-layer sequence across the entire PSC. These mechanisms are discussed in the contexts of chemical reactions, photo-physical management, technological modification, etc., which may inspire future R&D for stable PSCs. Finally, emerging operational stability standards with respect to testing and reporting device operational stability are summarized and discussed, which may help reliable device stability data circulate in the research community. The main target of this review is gaining insight into the operational stability of PSCs, as well as providing useful guidance to further improve their operational lifetime by rational materials processing and device fabrication, which would finally promote the commercialization of perovskite solar cells.

Towards commercialization: the operational stability of perovskite solar cells

Since the first introduction of the organic–inorganic hybrid perovskite in the field of optoelectronics, extraordinary progress in both the photoelectric-conversion-efficiency and stability of perovskite solar cells (PSCs) have been witnessed. However, a variety of drawbacks associated with defects in PSCs, such as energy deficits, ion migration, operational instability and hysteresis, greatly hinder the potential industrial applications of PSCs. Herein, a systematic and comprehensive understanding of the origin, classification, nature, relationships and overlapping effects of defects in perovskite is summarized and reviewed. According to their positions in the energy structure relative to band edges, shallow- and deep-level defects are summarized, while point defects, undercoordinated ions, impurities and pinholes are categorized based on a dimension-criterion. We look at the established understanding of how the detrimental defects induce non-radiative recombination, charge trapping and scattering, ion migration and hysteresis, providing a relatively clear relationship between the performance and defects in perovskite films. An overview of the defect passivation strategies is presented on the fabrication route, including film formation, post-treatment and interlayer engineering between the perovskite layer and charge transport layer, giving a unique perspective. Based on defect passivation engineering, challenges and suggestions to break the bottlenecks of PSCs on the way to commercialization are proposed.

Defect passivation strategies in perovskites for an enhanced photovoltaic performance

There is little question that the "electronic revolution" of the 20th century has impacted almost every aspect of human life However, the emergence of solid-state electronics as a ubiquitous feature of an advanced modern society is posing new challenges such as the management of electronic waste (e-waste) that will remain through the 21st century In addition to developing strategies to manage such e-waste, further challenges can be identified concerning the conservation and recycling of scarce elements, reducing the use of toxic materials and solvents in electronics processing, and lowering energy usage during fabrication methods In response to these issues, the construction of electronic devices from renewable or biodegradable materials that decompose to harmless by-products is becoming a topic of great interest Such "green" electronic devices need to be fabricated on industrial scale through low-energy and low-cost methods that involve low/non-toxic functional materials or solvents This review highlights recent advances in the development of biodegradable materials and processing strategies for electronics with an emphasis on areas where green electronic devices show the greatest promise, including solar cells, organic field-effect transistors, light-emitting diodes, and other electronic devices

Biodegradable Materials and Green Processing for Green Electronics.

The fast evolution of metal halide perovskite solar cells has opened a new chapter in the field of renewable energy. High-quality perovskite films as the active layers are essential for both high efficiency and long-term stability. Here, the perovskite films with enlarged crystal grain size and decreased defect density are fabricated by introducing the extremely low-cost and green polymer, ethyl cellulose (EC), into the perovskite layer. The addition of EC triggers hydrogen bonding interactions between EC and the perovskite, passivating the charge defect traps at the grain boundaries. The long chain of EC further acts as a scaffold for the perovskite structure, eliminating the annealing-induced lattice strain during the film fabrication process. The resulting devices with the EC additive exhibit a remarkably enhanced average power conversion efficiency from 17.11 to 19.27% and an improvement of all device parameters. The hysteresis index is found to decrease by three times from 0.081 to 0.027, which is attributed to suppressed ion migration and surface charge trapping. In addition, the defect passivation by EC significantly improves the environmental stability of the perovskite films, yielding devices that retain 80% of their initial efficiency after 30 days in ambient air at 45% relative humidity, whereas the pristine devices without EC fully degrade. This work provides a low-cost and green avenue for passivating defects that improves both the efficiency and operational stability of perovskite solar cells.

Extremely Low-Cost and Green Cellulose Passivating Perovskites for Stable and High-Performance Solar Cells

Biomimetic Electrodes for Flexible Organic Solar Cells with Efficiencies over 16

The visual aesthetic that involves color, brightness, and glossiness is of great importance for building integrated photovoltaics. Semitransparent organic solar cells (ST-OSCs) are thus considered as the most promising candidate due to their superiority in transparency and efficiency. However, the realization of high color purity with narrow bandpass transmitted light usually causes the severely suppressed transparency in ST-OSCs. Herein, we present a spectrally selective electrode (SSE) by imitating the integrating strategy of beetle cuticle for achieving narrow bandpass ST-OSCs with high efficiency and long-term stability. The proposed SSE allows for efficient light-selective passage, leading to tunable narrow bandpass transmitted light from violet to red. An optimized power conversion efficiency of 15.07% is achieved for colorful ST-OSCs, which exhibit color purity close to 100% and a peak transmittance approaching 30%. Long-term stability is also improved for ST-OSCs made with this SSE due to the light-rejecting and the moisture-blocking abilities. The realization of bright and colorful ST-OSCs also indicates the application potential of SSEs in light-emitting diodes, lasers, and photodetectors.

Narrow Bandpass and Efficient Semitransparent Organic Solar Cells Based on Bioinspired Spectrally Selective Electrodes.

Surface Plasmon‐Assisted Transparent Conductive Electrode for Flexible Perovskite Solar Cells

The invention relates to a preparation method for a high-haze polyimide film. The preparation method comprises the following steps: dissolving a fluorine-containing diamine monomer and a dianhydride monomer into a polar aprotic solvent so as to obtain a brownish yellow polyimidic acid solution; adding PS microspheres into the polyimidic acid solution, and carrying out uniform mixing so as to obtain a PS microsphere mixed polyimidic acid solution; and coating the PS microsphere mixed polyimidic acid solution onto the surface of a substrate, carrying out curing under heating, carrying out dehydration condensation so as to form a polyimide film, and carrying out cooling to a room temperature so as to form the high-haze polyimide film on the surface of the substrate. The method provided by theinvention has simple process, forms an effective light regulating and controlling structure in the polyimide film, and obtains a polyimide composite film with high light transmittance and high haze.

Qu Tianyi

Papers

Extremely Low-Cost and Green Cellulose Passivating Perovskites for Stable and High-Performance Solar Cells

Biomimetic Electrodes for Flexible Organic Solar Cells with Efficiencies over 16

Narrow Bandpass and Efficient Semitransparent Organic Solar Cells Based on Bioinspired Spectrally Selective Electrodes.

Surface Plasmon‐Assisted Transparent Conductive Electrode for Flexible Perovskite Solar Cells

High-haze polyimide film and preparation method thereof