Top 10 most influential scientists in Perocskite Solar Cells

Top 10 most influential scientists in Perovskite Solar Cells

● Tsutomu Miyasaka, Toin University of Yokohama

Miyasaka’s long term experience and research has been focused on the design of low-temperature solution-printing process for fabrication of dye-sensitized solar cells and solid-state hybrid photovoltaic cells. Also, he developed photovoltaic cells using organo-lead halide compounds as light-absorbing materials---perovskite solar cells. Miyasaka has contributed to the pioneering works and discovered perovskite’s potential as low-cost, large-area high-efficiency thin film solar cells. His first paper on perovskite solar cells published in 2009 has been cited more than 4400 times. Now Miyasaka group has been endeavoring in practical applications of perovskite solar cells and dye-sensitized solar cells, plus these technologies to flexible devices and photodetectors.

● Nam-Gyu Park, Sungkyunkwan University

Nam-Gyu’s research has been focused on high efficiency dye-sensitized solar cells. He is specialist in design and synthesis of inorganic nanostructured materials as well as perovskite solar cells.

Nam-Gyu had worked with Michael Grätzel (École Polytechnique Fédérale de Lausanne) and reported on solid-state mesoscopic heterojunction solar cells employing nanoparticles (NPs) of methyl ammonium lead iodide (CH3NH3)PbI3 as light harvesters in 2012. 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.

● Henry J. Snaith, University of Oxford

Snaith has made several significant advances for solution-processed solar cells, including the first demonstration of gyroid structured titania for dye solar cells. In 2012, Snaith has discovered the remarkable PV properties of metal halide perovskite which has emerged as a new field in PV research.

Snaith teamed up with Miyasaka, used spiro-OMeTAD as the hole-conducting layer, and deposited it on a mixed halide perovskite, CH3NH3Pbl2Cl. When the team made solar cells with those compounds and TiO2, they observed conversion efficiencies near 7.6 %, a value that just a year earlier would have turned heads. But when they replaced TiO2 with alumina (Al2O3), an insulator that cannot conduct electrons to the electrode---that is, when they made a solar cell that was sure to fail---it surprisingly delivered near 11 % conversion efficiency. The team proposed that alumina serves only as a high-surface-area scaffold but that it mediates formation of a layer of high-quality perovskite crystals. Snaith group suggested that the quality of the film is likely the reason the crystals can collect and transport electrons so efficiently. (Science 2012, DOI: 10.1126/science.1228604)

● Michael Grätzel, École Polytechnique Fédérale de Lausanne, EPFL

- 2013, Grätzel published a research paper ”Sequential deposition as a route to high-performance perovskite-sensitized solar cells.” (Nature volume499, pages316–319 (18 July 2013))
Following pioneering work, solution-processable organic–inorganic hybrid perovskites—such as CH3NH3PbX3 (X = Cl, Br, I)—have attracted attention as light-harvesting materials for mesoscopic solar cells. So far, the perovskite pigment has been deposited in a single step onto mesoporous metal oxide films using a mixture of PbX2 and CH3NH3X in a common solvent. However, the uncontrolled precipitation of the perovskite produces large morphological variations, resulting in a wide spread of photovoltaic performance in the resulting devices, which hampers the prospects for practical applications. Here we describe a sequential deposition method for the formation of the perovskite pigment within the porous metal oxide film. PbI2 is first introduced from solution into a nanoporous titanium dioxide film and subsequently transformed into the perovskite by exposing it to a solution of CH3NH3I. We find that the conversion occurs within the nanoporous host as soon as the two components come into contact, permitting much better control over the perovskite morphology than is possible with the previously employed route. Using this technique for the fabrication of solid-state mesoscopic solar cells greatly increases the reproducibility of their performance and allows us to achieve a power conversion efficiency of approximately 15 % (measured under standard AM1.5G test conditions on solar zenith angle, solar light intensity and cell temperature). This two-step method should provide new opportunities for the fabrication of solution-processed photovoltaic cells with unprecedented power conversion efficiencies and high stability equal to or even greater than those of today’s best thin-film photovoltaic devices.

- 2017, Grätzel published a research paper “ Perovskite solar cells with CuSCN hole extraction layers yield stabilized efficiencies greater than 20%”. (Science 28 Sep 2017:eaam5655; DOI: 10.1126/science.aam5655)
Perovskite solar cells (PSC) with efficiencies >20% have only been realized with highly expensive organic hole-transporting materials. We demonstrate PSCs achieving stabilized efficiencies exceeding 20% with CuSCN as hole extraction layer using fast solvent removal method to create compact, highly conformal CuSCN layers that facilitate fast carrier extraction and collection. The PSCs showed high thermal stability under long term heating, however, their operational stability was poor. This instability originates from potential induced degradation of the CuSCN/Au contact. The addition of a conductive reduced graphene oxide spacer layer between CuSCN and gold allowed PSCs to retain >95% of their initial efficiency after aging at a maximum power point for 1000 hours at 60 Celsius. Importantly, under both continuous full-sun illumination and thermal stress, CuSCN based devices surpassed the stability of spiro-OMeTAD based PSCs.

● Yang Yang, University of California, Los Angeles, UCLA

- 2014, Yang Yang published a research paper “Interface engineering of highly efficient perovskite solar cells.” (Science 01 Aug 2014:Vol. 345, Issue 6196, pp. 542-546; DOI: 10.1126/science.1254050)

Advancing perovskite solar cell technologies toward their theoretical power conversion efficiency (PCE) requires delicate control over the carrier dynamics throughout the entire device. By controlling the formation of the perovskite layer and careful choices of other materials, we suppressed carrier recombination in the absorber, facilitated carrier injection into the carrier transport layers, and maintained good carrier extraction at the electrodes. When measured via reverse bias scan, cell PCE is typically boosted to 16.6% on average, with the highest efficiency of ~19.3% in a planar geometry without antireflective coating. The fabrication of our perovskite solar cells was conducted in air and from solution at low temperatures, which should simplify manufacturing of large-area perovskite devices that are inexpensive and perform at high levels.

And Yang Yang Lab utilizes Enli Tech QE-R Solar Cell Quantum Efficiency Measurement System to measure quantum efficiency for solar cells.

● Sang Il Seok, Ulsan National Institute of Science and Technology

- 2017, Sang ll Seok has focused on inorganic-organic hybrid solar cells and perovskite solar cells. He published a research paper” Iodide management in formamidinium-lead-halide–based perovskite lay ers for efficient solar cells. ” (Published 2017 in Science; DOI:10.1126/science.aan2301)

In this study, the research team demonstrated the introduction of additional iodide ions into the organic cation solution, which are used to form the perovskite layers through an intramolecular exchanging process, decreases the concentration of deep-level defects. The formation of a dense and uniform thin layer on the substrates is crucial for the fabrication of high-performance perovskite solar cells (PSCs) containing formamidinium with multiple cations and mixed halide anions. The concentration of defect states, which reduce a cell’s performance by decreasing the open-circuit voltage and short-circuit current density, needs to be as low as possible. We show that the introduction of additional iodide ions into the organic cation solution, which are used to form the perovskite layers through an intramolecular exchanging process, decreases the concentration of deep-level defects. The defect-engineered thin perovskite layers enable the fabrication of PSCs with a certified power conversion efficiency of 22.1% in small cells and 19.7% in 1-square-centimeter cells.

● Liyuan Han, Shanghai Jiao Tong University

- 2017, Liyuan Han published a research paper” A solvent- and vacuum-free route to large-area perovskite films for efficient solar modules.” (Nature volume 550, pages 92–95 (05 October 2017))

The method produces homogenous films with relatively few defects, which leads to a record efficiency of 12.1% for a solar module made from a methylammonium lead halide film that is just over 36 cm2 in size.

Recent advances in the use of organic–inorganic hybrid perovskites for optoelectronics have been rapid, with reported power conversion efficiencies of up to 22 % for perovskite solar cells. Improvements in stability have also enabled testing over a timescale of thousands of hours. However, large-scale deployment of such cells will also require the ability to produce large-area, uniformly high-quality perovskite films. A key challenge is to overcome the substantial reduction in power conversion efficiency when a small device is scaled up: a reduction from over 20 % to about 10 per cent is found when a common aperture area of about 0.1 square centimetres is increased to more than 25 square centimetres. Here we report a new deposition route for methyl ammonium lead halide perovskite films that does not rely on use of a common solvent or vacuum: rather, it relies on the rapid conversion of amine complex precursors to perovskite films, followed by a pressure application step. The deposited perovskite films were free of pin-holes and highly uniform. Importantly, the new deposition approach can be performed in air at low temperatures, facilitating fabrication of large-area perovskite devices. We reached a certified power conversion efficiency of 12.1 % with an aperture area of 36.1 square centimetres for a mesoporous TiO2-based perovskite solar module architecture.

● Yi-Bing Cheng, Wuhan University of Technology

- 2018, Yi-Bing Cheng published a research paper” Influence of Hot Spot Heating on Stability of Large Size Perovskite Solar Module with a Power Conversion Efficiency of ~14%.” (ACS Appl. Energy Mater., 2018, 1 (8), pp 3565–3570; DOI: 10.1021/acsaem.8b00803; Publication Date (Web): July 16, 2018)

Making perovskite solar cell technology commercially viable is facing a challenge that scaling-up of a small device always experiences a substantial reduction in power conversion efficiency (PCE). In this research, we adopted a volume expansion routine to scale-up from a 0.16 cm2laboratory-scale device to large size perovskite solar module (PSM) with a PCE loss of 8% and reached a certified PCE of 13.98%. The PCE of the PSM with Au electrode dropped about 40% of the initial efficiency after 16 days’ storage, while the efficiency of PSM with Cu as counter electrode retained 90% of the initial after 30 days’ storage. We also introduced hot spots heating (HSH) characterization method to investigate the stability of PSM. HSH reveals that Cu electrode greatly reduces numbers of hot spots and extent of temperature increase in a PSM compared with Au electrode. Therefore, counter electrode also plays an important role in the stability improvement of PSM.

● Michael D. McGehee, Stanford University

- 2017, Michael D. McGehee published a research paper” 23.6%-efficient monolithic perovskite/silicon tandem solar cells with improved stability.” (Nature Energy volume 2, Article number: 17009 (2017))

As the record single-junction efficiencies of perovskite solar cells now rival those of copper indium gallium selenide, cadmium telluride and multicrystalline silicon, they are becoming increasingly attractive for use in tandem solar cells due to their wide, tunable bandgap and solution processability. Previously, perovskite/silicon tandems were limited by significant parasitic absorption and poor environmental stability. Here, we improve the efficiency of monolithic, two-terminal, 1-cm2 perovskite/silicon tandems to 23.6% by combining an infrared-tuned silicon heterojunction bottom cell with the recently developed caesium formamidinium lead halide perovskite. This more-stable perovskite tolerates deposition of a tin oxide buffer layer via atomic layer deposition that prevents shunts, has negligible parasitic absorption, and allows for the sputter deposition of a transparent top electrode. Furthermore, the window layer doubles as a diffusion barrier, increasing the thermal and environmental stability to enable perovskite devices that withstand a 1,000-hour damp heat test at 85 ℃ and 85% relative humidity.

● Jingbi You, Institute of Semiconductors, Chinese Academy of Sciences

- 2018, Jingbi You developed the latest perovskite solar cells, the highest power conversion efficiency up to 23.3 % in 2018. During the same year, he published a research paper” Efficient green light-emitting diodes based on quasi-two-dimensional composition and phase engineered perovskite with surface passivation.” (Nature Communications volume 9, Article number: 570 (2018)) And Jingbi You group utilizes Enli Tech LED Photo-Luminescence Quantum Yield Measurement System to measure external quantum efficiency up to 10 %.

- In perovskite solar cell field, Jingbi You published a research paper” A polymer tandem solar cell with 10.6% power conversion efficiency.” (Nature Communications volume 4, Article number: 1446 (2013))

An effective way to improve polymer solar cell efficiency is to use a tandem structure, as a broader part of the spectrum of solar radiation is used and the thermalization loss of photon energy is minimized. In the past, the lack of high-performance low-bandgap polymers was the major limiting factor for achieving high-performance tandem solar cell. Here we report the development of a high-performance low bandgap polymer (bandgap <1.4 eV), poly[2,7-(5,5-bis-(3,7-dimethyloctyl)-5H-dithieno[3,2-b:2′,3′-d]pyran)-alt-4,7-(5,6-difluoro-2,1,3-benzothia diazole)] with a bandgap of 1.38 eV, high mobility, deep highest occupied molecular orbital. As a result, a single-junction device shows high external quantum efficiency of >60% and spectral response that extends to 900 nm, with a power conversion efficiency of 7.9%. The polymer enables a solution processed tandem solar cell with certified 10.6% power conversion efficiency under standard reporting conditions (25 °C, 1,000 Wm-2, IEC 60904-3 global), which is the first certified polymer solar cell efficiency over 10%.

- In 2014, he published a research paper” Low-Temperature Solution-Processed Perovskite Solar Cells with High Efficiency and Flexibility.” (ACS Nano, 2014, 8 (2), pp 1674–1680; DOI: 10.1021/nn406020d; Publication Date (Web): January 5, 2014)

Perovskite compounds have attracted recently great attention in photovoltaic research. The devices are typically fabricated using condensed or mesoporous TiO2 as the electron transport layer and 2,2′7,7′-tetrakis-(N,N-dip-methoxyphenylamine)9,9′-spirobifluorene as the hole transport layer. However, the high-temperature processing (450 °C) requirement of the TiO2 layer could hinder the widespread adoption of the technology. In this report, we adopted a low-temperature processing technique to attain high-efficiency devices in both rigid and flexible substrates, using device structure substrate/ITO/PEDOT:PSS/CH3NH3PbI3–xClx/PCBM/Al, where PEDOT:PSS and PCBM are used as hole and electron transport layers, respectively. Mixed halide perovskite, CH3NH3PbI3–xClx, was used due to its long carrier lifetime and good electrical properties. All of these layers are solution-processed under 120 °C. Based on the proposed device structure, power conversion efficiency (PCE) of 11.5% is obtained in rigid substrates (glass/ITO), and a 9.2% PCE is achieved for a polyethylene terephthalate/ITO flexible substrate.

References:

Tsutimu (Tom) Miyasaka
http://ceramics.org/tsutomu-tom-miyasaka

Nam-Gyu Park, (2012) Lead Iodide Perovskite Sensitized All-Solid-State Submicron Thin Film Mesoscopic Solar Cell with Efficiency Exceeding 9%.
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3423636/

Mitch Jacoby, Chemical & Engineering News (2014) Tapping Solar Power with Perovskites
https://cbe.nd.edu/news/tapping-solar-power-with-perovskites

Michael Grätzel, (2014). Sequential deposition as a route to high-performance perovskite-sensitized solar cells
https://www.nature.com/articles/nature12340

Michael Grätzel, (2017). Perovskite solar cells with CuSCN hole extraction layers yield stabilized efficiencies greater than 20%
http://science.sciencemag.org/content/early/2017/09/27/science.aam5655

Sang Il Seok, (2017). Iodide management in formamidinium-lead-halide–based perovskite layers for efficient solar cells
https://goo.gl/GnjKsa

The OSA DIRECT NEWSLETTER, (2018). Large-area perovskite films go solvent- and vacuum-free
https://goo.gl/zHeD2G

Michael D. McGehee, (2017). 23.6%-efficient monolithic perovskite/silicon tandem solar cells with improved stability
https://www.nature.com/articles/nenergy20179

Yibing Cheng, (2018). Influence of Hot Spot Heating on Stability of Large Size Perovskite Solar Module with a Power Conversion Efficiency of ~14%
https://pubs.acs.org/doi/abs/10.1021/acsaem.8b00803

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