In the past ten years, perovskite solar cells (PSCs) have achieved tremendous success, with the efficiency rivalling that of conventional silicon-based devices. To promote commercialization, lowering ...the production cost and reducing the complexity of the process would make the devices more competitive and thus are highly required. In this respect, inverted hole-transport-layer-free (HTL-free) PSCs were developed and have been attracting extensive attention. To date, the efficiency of inverted HTL-free PSCs has surpassed 20%, and 90% of the initial efficiency can be retained after 1000 h of continuous illumination, showing their great application potential. In this mini-review, we summarize the development and progress of inverted HTL-free PSCs. The universality of inverted HTL-free structures (including flexible and semi-transparent devices) and stability are also discussed. Finally, promising research directions are suggested to further advance the inverted HTL-free PSCs.
Inverted HTL-free PSCs show high PCE and stability, and will be further improved by component, interface and passivation engineering.
Here we demonstrate a radically different chemical route for the creation of HC(NH2)2PbI3 (FAPbI3) perovskite thin films. This approach entails a simple exposure of as-synthesized CH3NH3PbI3 ...(MAPbI3) perovskite thin films to HC(NH)NH2 (formamidine or FA) gas at 150 °C, which leads to rapid displacement of the MA+ cations by FA+ cations in the perovskite structure. The resultant FAPbI3 perovskite thin films preserve the microstructural morphology of the original MAPbI3 thin films exceptionally well. Importantly, the myriad processing innovations that have led to the creation of high-quality MAPbI3 perovskite thin films are directly adaptable to FAPbI3 through this simple, rapid chemical-conversion route. Accordingly, we show that efficiencies of perovskite solar cells fabricated with FAPbI3 thin films created using this route can reach ∼18%.
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We report herein the discovery of methylamine (CH3NH2) induced defect‐healing (MIDH) of CH3NH3PbI3 perovskite thin films based on their ultrafast (seconds), reversible chemical reaction with CH3NH2 ...gas at room temperature. The key to this healing behavior is the formation and spreading of an intermediate CH3NH3PbI3⋅xCH3NH2 liquid phase during this unusual perovskite–gas interaction. We demonstrate the versatility and scalability of the MIDH process, and show dramatic enhancement in the performance of perovskite solar cells (PSCs) with MIDH. This study represents a new direction in the formation of defect‐free films of hybrid perovskites.
A perovskite smoothie: Treating CH3NH3PbI3 (MAPbI3) perovskite thin films with methylamine gas induces a rapid collapse of the perovskite structure and formation of a liquid phase. Removing the gas causes conversion back into the perovskite structure giving a smooth defect‐free film. Using the film in perovskite solar cells enhances their performance.
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A new generation of solid-state photovoltaics is being made possible by the use of organometal-trihalide perovskite materials. While some of these materials are expected to be ferroelectric, almost ...nothing is known about their ferroelectric properties experimentally. Using piezoforce microscopy (PFM), here we show unambiguously, for the first time, the presence of ferroelectric domains in high-quality β-CH3NH3PbI3 perovskite thin films that have been synthesized using a new solution-processing method. The size of the ferroelectric domains is found to be about the size of the grains (∼100 nm). We also present evidence for the reversible switching of the ferroelectric domains by poling with DC biases. This suggests the importance of further PFM investigations into the local ferroelectric behavior of hybrid perovskites, in particular in situ photoeffects. Such investigations could contribute toward the basic understanding of photovoltaic mechanisms in perovskite-based solar cells, which is essential for the further enhancement of the performance of these promising photovoltaics.
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Recently, organometal halide perovskite solar cells (PSCs) have attracted considerable attention because of their extremely high power conversion efficiency (PCE). Not only does the performance of ...PSCs depend on the material properties of the device involved, but also it is dramatically affected by the nature of their interfaces present, which highly affect the carriers' extraction, transport and recombination. Therefore, interface engineering, a novel approach towards high-performance PSCs, has attracted increasing interest. In this review, we focus on recent advances in the study of PSC interfaces, which have resulted in improved device performance.
In this review, we present recent advances in interface engineering at different interfaces in perovskite solar cells.
Graphene oxide (GO) nanosheets and polyoxometalate clusters, H3PW12O40 (PW), were co-assembled into multilayer films via electrostatic layer-by-layer assembly. Under UV irradiation, a photoreduction ...reaction took place in the films which converted GO to reduced GO (rGO) due to the photocatalytic activity of PW clusters. By this means, uniform and large-area composite films based on rGO were fabricated with precisely controlled thickness on various substrates such as quartz, silicon, and plastic supports. We further fabricated field effect transistors based on the composite films, which exhibited typical ambipolar features and good transport properties for both holes and electrons. The on/off ratios and the charge carrier mobilities of the transistors depend on the number of deposited layers and can be controlled easily. Furthermore, we used photomasks to produce conductive patterns of rGO domains on the films, which served as efficient microelectrodes for photodetector devices.
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A renewable and superior thermal-resistant cellulose-based composite nonwoven was explored as lithium-ion battery separator via an electrospinning technique followed by a dip-coating process. It was ...demonstrated that such nanofibrous composite nonwoven possessed good electrolyte wettability, excellent heat tolerance, and high ionic conductivity. The cells using the composite separator displayed better rate capability and enhanced capacity retention, when compared to those of commercialized polypropylene separator under the same conditions. These fascinating characteristics would endow this renewable composite nonwoven a promising separator for high-power lithium-ion battery.
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A replacement for gold as the hole‐injecting metal in organic electronic devices is presented: patterned graphene electrodes prepared from graphite oxide sheets by oxygen plasma etching. ...Solution‐processed organic FETs with poly(3‐hexylthiophene) as the semiconductor and these graphene electrodes are shown to perform as well as or even better than devices with gold contacts.
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9.
Doping and alloying for improved perovskite solar cells Zhou, Yuanyuan; Zhou, Zhongmin; Chen, Min ...
Journal of materials chemistry. A, Materials for energy and sustainability,
01/2016, Volume:
4, Issue:
45
Journal Article
Peer reviewed
Doping and/or alloying in the various layers in perovskite solar cells (PSCs) is playing a key role in the success of this new photovoltaic (PV) technology. Here we present a brief review of doping ...and alloying approaches used to enhance the efficacy of the hybrid organic-inorganic perovskite (HOIP) layer, the electron-transporting layer (ETL), the hole-transporting layer (HTL), and the electrode layers in PSCs. While the effectiveness of these approaches is beyond doubt, the fundamental understanding of doping and alloying in the majority of the cases is lacking. This presents vast research opportunities in elucidating the roles of doping and alloying, and the rational design and implementation of these approaches for enhanced PSCs performance.
Studies on doping and alloying for the advancement of perovskite solar cells are critically reviewed.
Formamidinium lead triiodide (HC(NH2)2PbI3 or FAPbI3) is gaining increasing interest in the field of mesoscopic perovskite solar cells (PSCs) for its broader light absorption compared with the more ...widely studied CH3NH3PbI3 (MAPbI3). Because FAPbI3 has two polymorphs (“black” α-FAPbI3 and “yellow” δ-FAPbI3) at ambient temperature, where α-FAPbI3 is the desirable photoactive perovskite phase, it becomes particularly important to suppress the formation of the nonperovskite δ-FAPbI3 for achieving high efficiency in FAPbI3-based mesoscopic PSCs. In this study, we demonstrate that the judicious use of low-volatility additives in the precursor solution assists in the evolution of α-FAPbI3 through the formation of non-δ-FAPbI3 intermediate phases, which then convert to α-FAPbI3 during thermal annealing. The underlying mechanism involved in the additive-modulated evolution of α-FAPbI3 upon mesoporous TiO2 substrates is elucidated, which suggests guidelines for developing protocols for the fabrication efficient FAPbI3-based mesoscopic PSCs.
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