Monolithic Perovskite Tandem Solar Cells: A Review of the Present Status and Advanced Characterization Methods Toward 30% Efficiency
About: This article is published in Advanced Energy Materials.The article was published on 2020-07-01 and is currently open access. It has received 266 citations till now. The article focuses on the topics: Perovskite (structure).
Citations
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TL;DR: A monolithic perovskite/silicon tandem with a certified power conversion efficiency of 29.15% is reported, made possible by a self-assembled, methyl-substituted carbazole monolayer as the hole-selective layer in the perovSKite cell.
Abstract: Tandem solar cells that pair silicon with a metal halide perovskite are a promising option for surpassing the single-cell efficiency limit. We report a monolithic perovskite/silicon tandem with a certified power conversion efficiency of 29.15%. The perovskite absorber, with a bandgap of 1.68 electron volts, remained phase-stable under illumination through a combination of fast hole extraction and minimized nonradiative recombination at the hole-selective interface. These features were made possible by a self-assembled, methyl-substituted carbazole monolayer as the hole-selective layer in the perovskite cell. The accelerated hole extraction was linked to a low ideality factor of 1.26 and single-junction fill factors of up to 84%, while enabling a tandem open-circuit voltage of as high as 1.92 volts. In air, without encapsulation, a tandem retained 95% of its initial efficiency after 300 hours of operation.
876 citations
TL;DR: Xiao et al. as mentioned in this paper used strongly reductive surface-anchoring zwitterionic molecules to suppress Sn2+ oxidation and passivate defects at the grain surfaces in mixed lead-tin perovskite films, enabling an efficiency of 21.7% (certified 20.7%).
Abstract: Monolithic all-perovskite tandem solar cells offer an avenue to increase power conversion efficiency beyond the limits of single-junction cells. It is an important priority to unite efficiency, uniformity and stability, yet this has proven challenging because of high trap density and ready oxidation in narrow-bandgap mixed lead–tin perovskite subcells. Here we report simultaneous enhancements in the efficiency, uniformity and stability of narrow-bandgap subcells using strongly reductive surface-anchoring zwitterionic molecules. The zwitterionic antioxidant inhibits Sn2+ oxidation and passivates defects at the grain surfaces in mixed lead–tin perovskite films, enabling an efficiency of 21.7% (certified 20.7%) for single-junction solar cells. We further obtain a certified efficiency of 24.2% in 1-cm2-area all-perovskite tandem cells and in-lab power conversion efficiencies of 25.6% and 21.4% for 0.049 cm2 and 12 cm2 devices, respectively. The encapsulated tandem devices retain 88% of their initial performance following 500 hours of operation at a device temperature of 54–60 °C under one-sun illumination in ambient conditions. Ensuring both stability and efficiency in mixed lead–tin perovskite solar cells is crucial to the development of all-perovskite tandems. Xiao et al. use an antioxidant zwitterionic molecule to suppress tin oxidation thus enabling large-area tandem cells with 24.2% efficiency and operational stability over 500 hours.
406 citations
TL;DR: An ammonium-cation-passivated Pb-Sn perovskites with long diffusion lengths are developed, enabling subcells having an absorber thickness of ~1.2 μm, and a certified efficiency of 26.4% in all-perovskite tandem solar cells is reported, exceeding that of the best-performing single-junction perovSKite solar cells.
352 citations
TL;DR: In this paper, the authors summarized the device design of PSCs and the physical properties of tin-based perovskites and discussed the major challenges for this field and discuss the essential techniques in film preparation.
Abstract: As a rising star of third-generation photovoltaic technology, organic–inorganic halide perovskite solar cells (PSCs) have exhibited high power conversion efficiency. However, the most investigated high-performance perovskites contain toxic lead, which may hinder their widespread applications. Among various alternative metal ions to replace lead for environmentally benign perovskites, tin has been successfully used in PSCs with the highest efficiency over 13% at present, making tin-based perovskites the most promising active materials for lead-free PSCs. In this review, we first summarize the device design of PSCs and the physical properties of tin-based perovskites. Then we state the major challenges for this field and discuss the essential techniques in film preparation. Specifically, tin rich conditions (tin halide) and suitable reducing agents are needed in the film preparation to prohibit Sn2+ oxidation, and solvent modulation is a feasible approach for controlling the film morphology. Meanwhile, chemical substitutions of A site and B site cations and X site anions to improve the optoelectronic properties of tin-based perovskites are comprehensively addressed. Moreover, tin–lead mixed perovskites that contain less lead than conventional perovskites for high-performance PSCs and tandem solar cells are discussed. This comprehensive review can shed light on the development of environmentally friendly PSCs and provide a guideline for realizing lead-free PSCs with high efficiency and stability via synergistic approaches.
188 citations
TL;DR: In this article, the development of tin oxide (SnO2 ) as a perovskite-relevant electron selective layer (ESL) is reviewed with emphasis placed on the various fabrication methods and interfacial passivation routes toward champion solar cells with high stability.
Abstract: Perovskite solar cells (PSCs) have become a promising photovoltaic (PV) technology, where the evolution of the electron-selective layers (ESLs), an integral part of any PV device, has played a distinctive role to their progress. To date, the mesoporous titanium dioxide (TiO2 )/compact TiO2 stack has been among the most used ESLs in state-of-the-art PSCs. However, this material requires high-temperature sintering and may induce hysteresis under operational conditions, raising concerns about its use toward commercialization. Recently, tin oxide (SnO2 ) has emerged as an attractive alternative ESL, thanks to its wide bandgap, high optical transmission, high carrier mobility, suitable band alignment with perovskites, and decent chemical stability. Additionally, its low-temperature processability enables compatibility with temperature-sensitive substrates, and thus flexible devices and tandem solar cells. Here, the notable developments of SnO2 as a perovskite-relevant ESL are reviewed with emphasis placed on the various fabrication methods and interfacial passivation routes toward champion solar cells with high stability. Further, a techno-economic analysis of SnO2 materials for large-scale deployment, together with a processing-toxicology assessment, is presented. Finally, a perspective on how SnO2 materials can be instrumental in successful large-scale module and perovskite-based tandem solar cell manufacturing is provided.
140 citations
References
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TL;DR: In this article, an upper theoretical limit for the efficiency of p−n junction solar energy converters, called the detailed balance limit of efficiency, has been calculated for an ideal case in which the only recombination mechanism of holeelectron pairs is radiative as required by the principle of detailed balance.
Abstract: In order to find an upper theoretical limit for the efficiency of p‐n junction solar energy converters, a limiting efficiency, called the detailed balance limit of efficiency, has been calculated for an ideal case in which the only recombination mechanism of hole‐electron pairs is radiative as required by the principle of detailed balance. The efficiency is also calculated for the case in which radiative recombination is only a fixed fraction fc of the total recombination, the rest being nonradiative. Efficiencies at the matched loads have been calculated with band gap and fc as parameters, the sun and cell being assumed to be blackbodies with temperatures of 6000°K and 300°K, respectively. The maximum efficiency is found to be 30% for an energy gap of 1.1 ev and fc = 1. Actual junctions do not obey the predicted current‐voltage relationship, and reasons for the difference and its relevance to efficiency are discussed.
11,071 citations
TL;DR: In this paper, the authors used a Geiger counter spectrometer to measure the changes in intensity distribution in the spectra of cold worked aluminium and wolfram and found that the line breadths may be attributed to simultaneous small particle size and strain broadening, the latter predominating at the higher Bragg angles.
7,802 citations
TL;DR: The authors show the double-slit interference effect in the strong-field ionization of neon dimers by employing COLTRIMS method to record the momentum distribution of the photoelectrons in the molecular frame.
Abstract: Wave-particle duality is an inherent peculiarity of the quantum world. The double-slit experiment has been frequently used for understanding different aspects of this fundamental concept. The occurrence of interference rests on the lack of which-way information and on the absence of decoherence mechanisms, which could scramble the wave fronts. Here, we report on the observation of two-center interference in the molecular-frame photoelectron momentum distribution upon ionization of the neon dimer by a strong laser field. Postselection of ions, which are measured in coincidence with electrons, allows choosing the symmetry of the residual ion, leading to observation of both, gerade and ungerade, types of interference.
7,160 citations
TL;DR: The use of a solid hole conductor dramatically improved the device stability compared to (CH3NH3)PbI3 -sensitized liquid junction cells.
Abstract: We report on solid-state mesoscopic heterojunction solar cells employing nanoparticles (NPs) of methyl ammonium lead iodide (CH3NH3)PbI3 as light harvesters. The perovskite NPs were produced by reaction of methylammonium iodide with PbI2 and deposited onto a submicron-thick mesoscopic TiO2 film, whose pores were infiltrated with the hole-conductor spiro-MeOTAD. Illumination with standard AM-1.5 sunlight generated large photocurrents (JSC) exceeding 17 mA/cm2, an open circuit photovoltage (VOC) of 0.888 V and a fill factor (FF) of 0.62 yielding a power conversion efficiency (PCE) of 9.7%, the highest reported to date for such cells. Femto second laser studies combined with photo-induced absorption measurements showed charge separation to proceed via hole injection from the excited (CH3NH3)PbI3 NPs into the spiro-MeOTAD followed by electron transfer to the mesoscopic TiO2 film. The use of a solid hole conductor dramatically improved the device stability compared to (CH3NH3)PbI3 -sensitized liquid junction cells.
6,751 citations
TL;DR: Physical structure is known to contribute to the appearance of bird plumage through structural color and specular reflection, but a third mechanism, structural absorption, leads to low reflectance and super black color in birds of paradise feathers.
Abstract: Many studies have shown how pigments and internal nanostructures generate color in nature. External surface structures can also influence appearance, such as by causing multiple scattering of light (structural absorption) to produce a velvety, super black appearance. Here we show that feathers from five species of birds of paradise (Aves: Paradisaeidae) structurally absorb incident light to produce extremely low-reflectance, super black plumages. Directional reflectance of these feathers (0.05-0.31%) approaches that of man-made ultra-absorbent materials. SEM, nano-CT, and ray-tracing simulations show that super black feathers have titled arrays of highly modified barbules, which cause more multiple scattering, resulting in more structural absorption, than normal black feathers. Super black feathers have an extreme directional reflectance bias and appear darkest when viewed from the distal direction. We hypothesize that structurally absorbing, super black plumage evolved through sensory bias to enhance the perceived brilliance of adjacent color patches during courtship display.
5,916 citations