Author
Spencer T. Williams
Bio: Spencer T. Williams is an academic researcher from University of Washington. The author has contributed to research in topics: Perovskite (structure) & Heterojunction. The author has an hindex of 22, co-authored 29 publications receiving 4683 citations.
Papers
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TL;DR: This work presents a probabilistic analysis of the chiral stationary phase transition of Na6(CO3)(SO4)2, a mixture of Na2CO3 and Na2SO4 which has shown promise as a raw material for high-performance liquid chromatography.
Abstract: P.-W. Liang, C.-Y. Liao, Dr. C.-C. Chueh, Dr. F. Zuo, S. T. Williams, Dr. X.-K. Xin, Prof. A. K.-Y. Jen Department of Materials Science and Engineering University of Washington Seattle , WA 98195 , USA E-mail: ajen@u.washington.edu Prof. A. K.-Y. Jen Department of Chemistry University of Washington Seattle , WA 98195 , USA C.-Y. Liao, Prof. J. J. Lin Institute of Polymer Science and Engineering National Taiwan University Taipei 106 , Taiwan
1,360 citations
TL;DR: An effective approach to significantly increase the electrical conductivity of a NiOx hole-transporting layer (HTL) to achieve high-efficiency planar heterojunction perovskite solar cells is demonstrated.
Abstract: An effective approach to significantly increase the electrical conductivity of a NiOx hole-transporting layer (HTL) to achieve high-efficiency planar heterojunction perovskite solar cells is demonstrated Perovskite solar cells based on using Cu-doped NiOx HTL show a remarkably improved power conversion efficiency up to 1540% due to the improved electrical conductivity and enhanced perovskite film quality General applicability of Cu-doped NiOx to larger bandgap perovskites is also demonstrated in this study
743 citations
TL;DR: High-performance non-fullerene OSCs with PCEs of up to ca.
Abstract: High-performance non-fullerene OSCs with PCEs of up to ca. 6.0% are demonstrated based on PBDTT-F-TT polymer and a molecular di-PBI acceptor through comprehensive molecular, interfacial, and device engineering. Impressive PCEs can also be retained in devices with relatively thick BHJ layer and processed through non-halogenated solvents, indicating these high-performance non-fullerene OSCs are promising for large-area printing applications.
396 citations
TL;DR: By employing the through-plane TEM analysis, this work gains detailed insight into the unique crystallographic textures, grain structures, and elemental distributions across the breadth of films grown from precursor solutions with different chemistries.
Abstract: A comprehensive morphological study was used to elucidate chloride’s role in CH3NH3PbI3–xClx film evolution on a conducting polymer, PEDOT:PSS. Complex ion equilibria and aggregation in solution, as well as the role they play in nucleation, are found to ultimately be responsible for the unique morphological diversity observed in perovskite films grown in the presence of the chloride ion. An intermediate phase that is generated upon deposition and initial annealing templates continued self-assembly in the case of CH3NH3PbI3–xClx. In the absence of chloride, the film growth of CH3NH3PbI3 is directed by substrate interfacial energy. By employing the through-plane TEM analysis, we gain detailed insight into the unique crystallographic textures, grain structures, and elemental distributions across the breadth of films grown from precursor solutions with different chemistries. The lattice coherence seen in morphologies generated under the influence of chloride provides a physical rational for the enhancement in...
355 citations
TL;DR: In this article, a spin and blade-coating process was applied to the preparation of CH 3 NH 3 PbI 3x Cl x perovskite cells to achieve high quality and moisture/air-resistant properties under ambient conditions.
Abstract: DOI: 10.1002/aenm.201401229 that the blade-coating process encourages the formation of self-assembled large perovskite crystalline domains featuring uniform fi lm coverage and signifi cantly improved device ambient stability. In addition, we reveal that this blade-coating process can also be applicable to systems based on using the advanced solvent engineering technique reported for high-performance perovskite (CH 3 NH 3 PbI 3 ) solar cells. [ 35,36 ] Blade-coating is a simple, cost-effi cient, and roll-to-roll compatible process for optoelectronic device fabrication. [ 37,38 ] In the case of perovskites, we fi nd that the formation of large crystalline domains is encouraged by the relatively slow solvent drying process in the uniformly wet fi lm formed immediately after solution blading. It may change the nucleation kinetics of perovskites to ensure self-assembly driven growth. Taking advantage of this process, we have applied blade-coating to the preparation of CH 3 NH 3 PbI 3x Cl x perovskite fi lms to achieve high quality and moisture/air-resistant fi lms under ambient conditions. To examine the processability of perovskite fi lms in ambient and explore the effect of different coating methods on device performance, we have fabricated perovsktie solar cells using both spinand blade-coating. The fi lms were annealed at 90 °C in air for 2 h after both coating processes; but in the case of bladecoating, the wet fi lms formed immediately after solution blading were kept at room temperature for 40 min before annealing to wait for the majority of N,N -dimethylformamide (DMF) solvent to be evaporated. The same coating and annealing conditions were used for other perovskite fi lms studied later in this work. The device confi guration and energy band diagram of materials used in this study is shown in Figure 1 . [ 39,40 ]
333 citations
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TL;DR: Perovskite films received a boost in photovoltaic efficiency through controlled formation of charge-generating films and improved current transfer to the electrodes and low-temperature processing steps allowed the use of materials that draw current out of the perovskites layer more efficiently.
Abstract: 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.
5,789 citations
TL;DR: An approach for depositing high-quality FAPbI3 films, involving FAP bI3 crystallization by the direct intramolecular exchange of dimethylsulfoxide (DMSO) molecules intercalated in PbI2 with formamidinium iodide is reported.
Abstract: The band gap of formamidinium lead iodide (FAPbI3) perovskites allows broader absorption of the solar spectrum relative to conventional methylammonium lead iodide (MAPbI3). Because the optoelectronic properties of perovskite films are closely related to film quality, deposition of dense and uniform films is crucial for fabricating high-performance perovskite solar cells (PSCs). We report an approach for depositing high-quality FAPbI3 films, involving FAPbI3 crystallization by the direct intramolecular exchange of dimethylsulfoxide (DMSO) molecules intercalated in PbI2 with formamidinium iodide. This process produces FAPbI3 films with (111)-preferred crystallographic orientation, large-grained dense microstructures, and flat surfaces without residual PbI2. Using films prepared by this technique, we fabricated FAPbI3-based PSCs with maximum power conversion efficiency greater than 20%.
5,458 citations
TL;DR: A novel non-fullerene electron acceptor (ITIC) that overcomes some of the shortcomings of fullerene acceptors, for example, weak absorption in the visible spectral region and limited energy-level variability, is designed and synthesized.
Abstract: A novel non-fullerene electron acceptor (ITIC) that overcomes some of the shortcomings of fullerene acceptors, for example, weak absorption in the visible spectral region and limited energy-level variability, is designed and synthesized. Fullerene-free polymer solar cells (PSCs) based on the ITIC acceptor are demonstrated to exhibit power conversion effi ciencies of up to 6.8%, a record for fullerene-free PSCs.
3,048 citations
TL;DR: Thin films of near-single-crystalline quality are produced, in which the crystallographic planes of the inorganic perovskite component have a strongly preferential out-of-plane alignment with respect to the contacts in planar solar cells to facilitate efficient charge transport.
Abstract: Three-dimensional organic-inorganic perovskites have emerged as one of the most promising thin-film solar cell materials owing to their remarkable photophysical properties, which have led to power conversion efficiencies exceeding 20 per cent, with the prospect of further improvements towards the Shockley-Queisser limit for a single‐junction solar cell (33.5 per cent). Besides efficiency, another critical factor for photovoltaics and other optoelectronic applications is environmental stability and photostability under operating conditions. In contrast to their three-dimensional counterparts, Ruddlesden-Popper phases--layered two-dimensional perovskite films--have shown promising stability, but poor efficiency at only 4.73 per cent. This relatively poor efficiency is attributed to the inhibition of out-of-plane charge transport by the organic cations, which act like insulating spacing layers between the conducting inorganic slabs. Here we overcome this issue in layered perovskites by producing thin films of near-single-crystalline quality, in which the crystallographic planes of the inorganic perovskite component have a strongly preferential out-of-plane alignment with respect to the contacts in planar solar cells to facilitate efficient charge transport. We report a photovoltaic efficiency of 12.52 per cent with no hysteresis, and the devices exhibit greatly improved stability in comparison to their three-dimensional counterparts when subjected to light, humidity and heat stress tests. Unencapsulated two-dimensional perovskite devices retain over 60 per cent of their efficiency for over 2,250 hours under constant, standard (AM1.5G) illumination, and exhibit greater tolerance to 65 per cent relative humidity than do three-dimensional equivalents. When the devices are encapsulated, the layered devices do not show any degradation under constant AM1.5G illumination or humidity. We anticipate that these results will lead to the growth of single-crystalline, solution-processed, layered, hybrid, perovskite thin films, which are essential for high-performance opto-electronic devices with technologically relevant long-term stability.
2,566 citations
TL;DR: The broad tunability and fabrication methods of these materials, the current understanding of the operation of state-of-the-art solar cells and the properties that have delivered light-emitting diodes and lasers are described.
Abstract: Metal-halide perovskites are crystalline materials originally developed out of scientific curiosity. Unexpectedly, solar cells incorporating these perovskites are rapidly emerging as serious contenders to rival the leading photovoltaic technologies. Power conversion efficiencies have jumped from 3% to over 20% in just four years of academic research. Here, we review the rapid progress in perovskite solar cells, as well as their promising use in light-emitting devices. In particular, we describe the broad tunability and fabrication methods of these materials, the current understanding of the operation of state-of-the-art solar cells and we highlight the properties that have delivered light-emitting diodes and lasers. We discuss key thermal and operational stability challenges facing perovskites, and give an outlook of future research avenues that might bring perovskite technology to commercialization.
2,513 citations