Passivation and interlayer engineering are important approaches to increase the efficiency and stability of perovskite solar cells. Thin insulating dielectric films at the interface between the ...perovskite and the charge carrier transport layers have been suggested to passivate surface defects. Here, we analyze the effect of depositing poly(methyl methacrylate) (PMMA) from a very low-concentration solution. Spatial- and time-resolved photoluminescence and atomic force microscopy analyses of samples with diverse morphologies demonstrate the preferential deposition of PMMA in topographic depressions of the perovskite layer, such as grain and domain boundaries. This treatment results in an increase in the fill factor of more than 4% and an absolute efficiency boost exceeding 1%, with a maximum efficiency of 20.4%. Based on these results, we propose a physical isolation mechanism rather than a chemical passivation of perovskite defects, which explains not only the data of this study but also most results found in earlier works.
Organic–inorganic perovskites are highly promising solar cell materials with laboratory-based power conversion efficiencies already matching those of established thin film technologies. Their ...exceptional photovoltaic performance is in part attributed to the presence of efficient radiative recombination pathways, thereby opening up the possibility of efficient light-emitting devices. Here, we demonstrate optically pumped amplified spontaneous emission (ASE) at 780 nm from a 50 nm-thick film of CH3NH3PbI3 perovskite that is sandwiched within a cavity composed of a thin-film (∼7 μm) cholesteric liquid crystal (CLC) reflector and a metal back-reflector. The threshold fluence for ASE in the perovskite film is reduced by at least two orders of magnitude in the presence of the CLC reflector, which results in a factor of two reduction in threshold fluence compared to previous reports. We consider this to be due to improved coupling of the oblique and out-of-plane modes that are reflected into the bulk in addition to any contributions from cavity modes. Furthermore, we also demonstrate enhanced ASE on flexible reflectors and discuss how improvements in the quality factor and reflectivity of the CLC layers could lead to single-mode lasing using CLC reflectors. Our work opens up the possibility of fabricating widely wavelength-tunable “mirror-less” single-mode lasers on flexible substrates, which could find use in applications such as flexible displays and friend or foe identification.
The discovery and development of organic–inorganic halide perovskites with exceptional properties has become an active research area in the field of photovoltaics. Perovskite solar cells (PSCs) have ...attracted much attention in recent years due to various attractive advantages, such as simple solution processing, low manufacturing cost, and high performances with power conversion efficiencies now reaching certified values close to 23% within a very short time frame of five years. Despite this rapid progress, the inferior device stability remains a great challenge. This review focuses on the factors limiting the stability of PSCs, such as humidity, heat, and irradiation, summarizing recent strategies to overcome stability and fabrication obstacles in order to open new perspectives to achieve highly durable perovskite devices toward future industrialization.
Efficiency, stability, and the cost of fabrication are the three edges of the triangle that represents the commercialization of perovskite solar cells. Overcoming the cell's stability against heat, light, and humidity is a key challenge for scalability.
Perovskite solar cells (PSCs) have emerged recently as promising candidates for next generation photovoltaics and have reached power conversion efficiencies of 25.2%. Among the various methods to ...advance solar cell technologies, the implementation of nanoparticles with plasmonic effects is an alternative way for photon and charge carrier management. Surface plasmons at the interfaces or surfaces of sophisticated metal nanostructures are able to interact with electromagnetic radiation. The properties of surface plasmons can be tuned specifically by controlling the shape, size, and dielectric environment of the metal nanostructures. Thus, incorporating metallic nanostructures in solar cells is reported as a possible strategy to explore the enhancement of energy conversion efficiency mainly in semi‐transparent solar cells. One particularly interesting option is PSCs with plasmonic structures enable thinner photovoltaic absorber layers without compromising their thickness while maintaining a high light harvest. In this Review, the effects of plasmonic nanostructures in electron transport material, perovskite absorbers, the hole transport material, as well as enhancement of effective refractive index of the medium and the resulting solar cell performance are presented. Aside from providing general considerations and a review of plasmonic nanostructures, the current efforts to introduce these plasmonic structures into semi‐transparent solar cells are outlined.
Implementation of nanoparticles (NPs) with plasmonic effects is an effective strategy for photon and charge dynamic management in perovskite solar cells (PSCs). The outstanding effects of plasmonic nanostructures such as Ag NPs decorated on TiO2 nanowires in electron transport materials as well as localized surface plasmon resonance of Au NPs in hole transport materials enhance the photovoltaic response of PSCs.
Triarylamine‐based polymers with different functional groups were synthetized as hole‐transport materials (HTMs) for perovskite solar cells (PSCs). The novel materials enabled efficient PSCs without ...the use of chemical doping (or additives) to enhance charge transport. Devices employing poly(triarylamine) with methylphenylethenyl functional groups (V873) showed a power conversion efficiency of 12.3 %, whereas widely used additive‐free polybis(4‐phenyl)(2,4,6‐trimethylphenyl)amine (PTAA) demonstrated 10.8 %. Notably, devices with V873 enabled stable PSCs under 1 sun illumination at maximum power point tracking for approximately 40 h at room temperature, and in the dark under elevated temperature (85 °C) for more than 140 h. This is in stark contrast to additive‐containing devices, which degrade significantly within the same time frame. The results present remarkable progress towards stable PSC under real working conditions and industrial stress tests.
PolyTPAs for stable PSCs: Poly(triarylamine) with methylphenylethenyl functional groups (V873) is used as a hole‐transporting material in perovskite solar cells (PSCs). Devices employing V873 reach a power conversion efficiency of 12.3 % without any additives, and enable stable operation under 1 sun at maximum power point tracking and under elevated temperature (85 °C). This result shows remarkable progress towards stable PSCs under real working conditions and industrial stress tests.
All‐inorganic perovskites have emerged as promising photovoltaic materials due to their superior thermal stability compared to their heat‐sensitive hybrid organic–inorganic counterparts. In ...particular, CsPbI2Br shows the highest potential for developing thermally‐stable perovskite solar cells (PSCs) among all‐inorganic compositions. However, controlling the crystallinity and morphology of all‐inorganic compositions is a significant challenge. Here, a simple, thermal gradient‐ and antisolvent‐free method is reported to control the crystallization of CsPbI2Br films. Optical in situ characterization is used to investigate the dynamic film formation during spin‐coating and annealing to understand and optimize the evolving film properties. This leads to high‐quality perovskite films with micrometer‐scale grain sizes with a noteworthy performance of 17% (≈16% stabilized), fill factor (FF) of 80.5%, and open‐circuit voltage (VOC) of 1.27 V. Moreover, excellent phase and thermal stability are demonstrated even after extreme thermal stressing at 300 °C.
A spin‐forced (SF) method as a facile approach is proposed to control the crystallization kinetics of CsPbI2Br crystal growth, achieving a uniform, and high‐quality film. The perovskite film formation during spin‐coating and annealing is evaluated by optical in situ characterization. As a result, an efficiency of 17.0% with excellent thermal stability at 300 °C is achieved.
The molecular structure of the hole transporting material (HTM) play an important role in hole extraction in a perovskite solar cells. It has a significant influence on the molecular planarity, ...energy level, and charge transport properties. Understanding the relationship between the chemical structure of the HTM's and perovskite solar cells (PSCs) performance is crucial for the continued development of the efficient organic charge transporting materials. Using molecular engineering approach we have constructed a series of the hole transporting materials with strategically placed aliphatic substituents to investigate the relationship between the chemical structure of the HTMs and the photovoltaic performance. PSCs employing the investigated HTMs demonstrate power conversion efficiency values in the range of 9% to 16.8% highlighting the importance of the optimal molecular structure. An inappropriately placed side group could compromise the device performance. Due to the ease of synthesis and moieties employed in its construction, it offers a wide range of possible structural modifications. This class of molecules has a great potential for structural optimization in order to realize simple and efficient small molecule based HTMs for perovskite solar cells application.
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