The ability to process amorphous or polycrystalline solar cells at low temperature (<150 °C) opens many possibilities for substrate choice and monolithic multijunction solar cell fabrication. ...Organometal trihalide perovskite solar cells have evolved rapidly over the last two years, and the CH 3 NH 3 PbX 3 (X = Cl, I or Br) material is processed at low temperature. However the first embodiments of the solar cell were composed of high temperature processed (500 °C) compact and mesoporous layers of TiO 2 . The sintering of the mesoporous TiO 2 has been negated by replacing this with a mesoporous insulating scaffold in the meso-superstructured solar cell (MSSC), yet the high temperature processed compact TiO 2 layer still persists in the most efficient devices. Here we have realised a low temperature route for compact TiO 2 , tailored for perovskite MSSC operation. With our optimized formulation we demonstrate full sun solar power conversion efficiencies of up to 15.9% in an all low temperature processed solar cell.
In material recovery facilities (MRFs) the sorting of waste is typically carried out predominantly manually. In this work, the MRF in Marsaskala, Malta is used as a case study to explore ways in ...which more automation can be employed to the sorting of commingled recyclable domestic waste. The work addresses first the conceptual design of the process layout and methods. This is followed by the detailed design and development of a universal gripper to replace the human sorter, aimed at removing contaminants from a stream of already sorted material, increasing the purity of the baled material and thereby increasing profits.
The achievement of high efficiency and high stability in perovskite solar cells (PSCs) requires optimal selection and evaluation of the various components. After a brief introduction to the ...perovskite materials and their historical evolution, the first part is devoted to the hole transporting material (HTM), between photoelectrode and dark counter electrode. The basic requirements for an efficient HTM are stated. Subsequently, the most used HTM, spiro-OMeTAD, is compared to alternative HTMs, both small-molecule size species and electronically conducting polymers. The second part is devoted to additives related to the performance of the perovskite light-absorbing material itself. These are related either to the modification of the composition of the material itself or to the optimization of the morphology during the perovskite preparation stage, and their effect is in the enhancement of the power conversion efficiency, the long-term stability, or the reproducibility of the properties of the PSCs. Finally, a number of spectroscopic methods based on the UV-Vis part of the electromagnetic spectrum useful for characterizing the different perovskite material types are described in the last part of this review.
Perovskite solar cells (PSCs) are currently one of the most promising photovoltaic technologies for highly efficient and cost-effective solar energy production. In only a few years, an unprecedented ...progression of preparation procedures and material compositions delivered lab-scale devices that have now reached record power conversion efficiencies (PCEs) higher than 20%, competing with most established solar cell materials such as silicon, CIGS, and CdTe. However, despite a large number of researchers currently involved in this topic, only a few groups in the world can reproduce >20% efficiencies on a regular n–i–p architecture. In this work, we present detailed protocols for preparing PSCs in regular (n–i–p) and inverted (p–i–n) architectures with ≥20% PCE. We aim to provide a comprehensive, reproducible description of our device fabrication protocols. We encourage the practice of reporting detailed and transparent protocols that can be more easily reproduced by other laboratories. A better reporting standard may, in turn, accelerate the development of perovskite solar cells and related research fields.
Organic–inorganic perovskite solar cells have achieved impressive power conversion efficiency over the past years, yet operational stability remains the key concern. One strategy to improve long‐term ...stability is to replace the thermally unstable organic with inorganic cations comprising the perovskite lattice. Here, for the first time, pulsed infrared light is used to drive the crystallization of inorganic mixed halide CsPbIxBr(3−x) perovskite films in solar cells with a power conversion efficiency exceeding 10%. By varying the iodide–bromine ratio systematically, it is found that to keep the inorganic perovskite black phase stable at the room temperature, the iodine content needs to be limited to lower than 60% – bromine content higher than 40%. The finding revises previous reports claiming stable compositions with higher iodine contents, which is systematically exploited to reduce the perovskite bandgap with the aim to enlarge the light absorption spectra and thus to boost the device efficiency. It is demonstrated that the newly defined stable compositional range enables devices that retain 90% of the efficiency after stressing the perovskite at 200 °C for 1 h. This result demonstrates that inorganic halide perovskites are stable materials for high‐temperature applications such as concentrated photovoltaics.
Replacing organic with the inorganic cations in halide perovskites is one of the most promising strategies to improve the operational stability of perovskite solar cells. This work demonstrates that pulsed infrared light crystallization of perovskite films enables over 10% efficient perovskite solar cells stable at 200 °C.
Recently organic-inorganic perovskite solar cells (PSCs) have emerged as promising candidates for photovoltaics because of their relatively high efficiency and low processing costs. However, for ...possible commercialisation, long-term stability remains a key obstacle, especially when compared to silicon or GaAs. Thus, future research will significantly focus on stability. The most relevant industry standards for the stability of solar cells are issued by the International Electrotechnical Commission (IEC), summarized in the so-called IEC 61215 norm. The IEC 61215 is a series of very detailed, time-consuming and interconnected stress tests that provide accelerated aging conditions to extrapolate the potential long-term lifetime of a solar module. Established silicon, for example, passes the full IEC 61215. To gain the confidence of investors and customers, passing the full IEC 61215 is a necessary minimum requirement for the commercialization of perovskites. Interestingly, the IEC 61215 is not openly accessible which may be one reason why there are often references to outdated versions. To remedy this situation, we introduce and analyse the most current IEC 61215 stability standards for solar cells and to which degree perovskites have passed them. We then elaborate on the most pertinent challenges for the long-term stability of PSCs in the coming years. This includes less explored stability tests such as potential-induced degradation (IEC TS 62804-1) and ammonia corrosion (IEC 62716). From this, it is evident that currently underappreciated degradation modes such as mechanical stability, high applied voltages and reverse bias, where especially hot spots could become problematic, must be considered in the coming years when evaluating the long-term stability of PSCs.
Perovskite solar cells have emerged as promising candidates for photovoltaics. Passing existing standards is a necessary minimum requirement for a possible commercialisation. Here, we analyse the most current international stability standards and to which degree perovskites have passed them. We then elaborate on the most pertinent challenges for the long-term stability of perovskites in the coming years.
Organic-inorganic perovskite structures in which lead is substituted by tin are exceptional candidates for broadband light absorption. Herein we present a thorough analysis of the optical properties ...of CH3NH3SnxPb1-xI3 films, providing the field with definitive insights about the possibilities of these materials for perovskite solar cells of superior efficiency. We report a user's guide based on the first set of optical constants obtained for a series of tin/lead perovskite films, which was only possible to measure due to the preparation of optical quality thin layers. According to the Shockley-Queisser theory, CH3NH3SnxPb1-xI3 compounds promise a substantial enhancement of both short circuit photocurrent and power conversion efficiency in single junction solar cells. Moreover, we propose a novel tandem architecture design in which both top and bottom cells are made of perovskite absorbers. Our calculations indicate that such perovskite-on-perovskite tandem devices could reach efficiencies over 35%. Our analysis serves to establish the first roadmap for this type of cells based on actual optical characterization data. We foresee that this study will encourage the research on novel near-infrared perovskite materials for photovoltaic applications, which may have implications in the rapidly emerging field of tandem devices.
We report the excellent scintillation properties of MAPbBr3, an organic–inorganic trihalide perovskite (OTP). The characteristic scintillation time constants were determined using pulsed ...monochromatic 14 keV X-rays from a synchrotron. We find that between 50 and 130 K the MAPbBr3 crystal exhibits a very fast and intense scintillation response, with the fast (τf) and slow (τs) decay components reaching 0.1 and 1 ns, respectively. The light yield of MAPbBr3 is estimated to be 90 000 ± 18 000 ph MeV−1 at 77 K and 116 000 ± 23 000 ph MeV−1 at 8 K.
Perovskite solar cells (PSCs) have now achieved efficiencies in excess of 22%, but very little is known about their long-term stability under thermal stress. So far, stability reports have hinted at ...the importance of substituting the organic components, but little attention has been given to the metal contact. We investigated the stability of state-of-the-art PSCs with efficiencies exceeding 20%. Remarkably, we found that exposing PSCs to a temperature of 70 °C is enough to induce gold migration through the hole-transporting layer (HTL), spiro-MeOTAD, and into the perovskite material, which in turn severely affects the device performance metrics under working conditions. Importantly, we found that the main cause of irreversible degradation is not due to decomposition of the organic and hybrid perovskite layers. By introducing a Cr metal interlayer between the HTL and gold electrode, high-temperature-induced irreversible long-term losses are avoided. This key finding is essential in the quest for achieving high efficiency, long-term stable PSCs which, in order to be commercially viable, need to withstand hard thermal stress tests.
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