Nucleation and growth processes can be effectively controlled in organic semiconductor films through a new concept of template‐mediated molecular crystal seeds during the phase transition; the ...effective control of these processes ensures millimeter‐scale crystal domains, as well as the performance of the resulting organic films with intrinsic hole mobility of 18 cm2 V–1 s–1.
Electro-spray (e-spray) is emerging as an attractive printing method for the thin-film fabrication of organic materials because of the simple apparatus and its high efficiency. Here, we demonstrate a ...fully e-sprayed organic solar cell (OSC) with high performance by using an additive in the poly(3-hexylthiophene):6,6-phenyl C61-butyric acid methyl ester (P3HT:PCBM) layer without any post-processing treatment. The P3HT:PCBM film fabricated with 6vol% 1,8-diiodooctane (DIO) showed improved surface macro- and nano-morphologies, which resulted in an enhanced photovoltaic performance. Using optimized conditions, we obtained a 2.98% efficient OSC (as-prepared condition) with the e-spray method, and post-annealing increased the power conversion efficiency (PCE) slightly to 3.08%.
► Electro-spray depositions of P3HT:PCBM bulk-heterojunction (BHJ) with additive were studied. ► BHJ with 6vol% 1,8-diiodooctane (DIO) showed the best macro- and nano-morphology. ► Power conversion efficiency of 2.98% was obtained by e-spray method even without any post treatment.
Efficient photovoltaic devices must be efficient light emitters to reach the thermodynamic efficiency limit. Here, we present a promising prospect of perovskite photovoltaics as bright emitters by ...harnessing the significant benefits of photon recycling, which can be practically achieved by suppressing interfacial quenching. We have achieved radiative and stable perovskite photovoltaic devices by the design of a multiple quantum well structure with long (∼3 nm) organic spacers with oleylammonium molecules at perovskite top interfaces. Our L-site exchange process (L: barrier molecule cation) enables the formation of stable interfacial structures with moderate conductivity despite the thick barriers. Compared to popular short (∼1 nm) Ls, our approach results in enhanced radiation efficiency through the recursive process of photon recycling. This leads to the realization of radiative perovskite photovoltaics with both high photovoltaic efficiency (in-lab 26.0%, certified to 25.2%) and electroluminescence quantum efficiency (19.7 % at peak, 17.8% at 1-sun equivalent condition). Furthermore, the stable crystallinity of oleylammonium-based quantum wells enables our devices to maintain high efficiencies for over 1000 h of operation and >2 years of storage.
We report chemically tunable n-type titanium oxides using ethanolamine as a nitrogen dopant source. As the amount of ethanolamine added to the titanium oxide precursor during synthesis increases, the ...Fermi level of the resulting titanium oxides (ethanolamine-incorporated titanium oxides) significantly changes from -4.9 eV to -4.3 eV, and their free charge carrier densities are enhanced by two orders of magnitudes, reaching up to 5 × 10
cm
. Unexpectedly, a basic ethanolamine reinforces not only the n-type properties of titanium oxides, but also their basicity, which facilitates acid-base ionic junctions in contact with acidic materials. The enhanced charge carrier density and basicity of the chemically tuned titanium oxides enable multi-junction solar cells to have interconnecting junctions consisting of basic n-type titanium oxides and acidic p-type PEDOT:PSS to gain high open-circuit voltages of 1.44 V and 2.25 V from tandem and triple architectures, respectively.
For semitransparent devices with n‐i‐p structures, a metal oxide buffer material is commonly used to protect the organic hole transporting layer from damage due to sputtering of the transparent ...conducting oxide. Here, a surface treatment approach is addressed for tungsten oxide‐based transparent electrodes through slight modification of the tungsten oxide surface with niobium oxide. Incorporation of this transparent electrode technique to the protective buffer layer significantly recovers the fill factor from 70.4% to 80.3%, approaching fill factor values of conventional opaque devices, which results in power conversion efficiencies over 18% for the semitransparent perovskite solar cells. Application of this approach to a four‐terminal tandem configuration with a silicon bottom cell is demonstrated.
A tungsten oxide (WOx) layer with niobium oxide surface treatment is introduced as a sputter buffer for semitransparent perovskite solar cells. Compared to devices with an untreated WOx buffer, using the surface‐treated buffer significantly recovers the fill factor, which is possibly explained via electronic‐trap shifting toward the band edge. Incorporation of this approach is demonstrated for four‐terminal perovskite‐silicon tandems.
Unlike typical inorganic semiconductors with a crystal structure, the charge dynamics of π-conjugated polymers (π-CPs) are severely limited by the presence of amorphous portions between the ordered ...crystalline regions. Thus, the formation of interconnected pathways along crystallites of π-CPs is desired to ensure highly efficient charge transport in printable electronics. Here we report the formation of nano-crystallite networks in π-CP films by employing novel template-mediated crystallization (TMC) via polaron formation and electrostatic interaction. The lateral and vertical charge transport of TMC-treated films increased by two orders of magnitude compared with pristine π-CPs. In particular, because of the unprecedented room temperature and solution-processing advantages of our TMC method, we achieve a field-effect mobility of 0.25 cm(2) V(-1) s(-1) using a plastic substrate, which corresponds to the highest value reported thus far. Because our findings can be applied to various π-conjugated semiconductors, our approach is universal and is expected to yield high-performance printable electronics.
For commercializing perovskite solar cells (PSCs), moisture-tolerant materials are required because a moisture-free environment cannot be maintained on an actual production line (large scale). ...Recently, PSCs with efficiency exceeding 22% have been fabricated using Li-doped mesoporous TiO2 as an electron transport layer (ETL). However, the use of Li can negatively influence device stability during the fabrication process under humid air because of its hydroscopic property. Here, we report a strategy for improving processing stability without sacrificing the power conversion efficiency (PCE) under a humid atmospheric environment by employing a mesoporous BaSnO3 as an ETL. Using the mesoporous BSO ETL, we achieved a certified efficiency of 21.3% and stabilized efficiency of 21.7%. Furthermore, the BSO-based PSCs also exhibited better processing stability than Li-doped TiO2-based PSCs under humid air. We believe that this strategy of introducing BSO into PSCs will accelerate the commercialization of PSCs.
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•Mesoporous BaSnO3 was employed as an electron transport material•The certified power conversion efficiency of 21.3% was achieved•BaSnO3 solar cells showed superior processing stability than Li-doped TiO2 solar cells•Encapsulated solar cells with BaSnO3 exhibit excellent photostability for 500 h
Organometal-halide perovskite solar cells (PSCs) have emerged as very promising next-generation solar cells owing to their low fabrication cost and remarkable power conversion efficiency (PCE) of more than 24%. With improving the PCE, stability issues have been raised for commercialization. Recently, much effort has been made to enhance the stability of the perovskite layer and the hole transporting layer, which has successfully improved the durability of the device. However, little research has been done on the humidity stability of the metal-oxide layer, especially conventional Li-doped TiO2. This issue is very important because moisture cannot be perfectly excluded in an actual production line. Herein, we provide deeper understanding of the degradation mechanism for Li-doped TiO2-based PSC under a humid environment and propose a new metal-oxide (BaSnO3) ETL to improve both device performance and processing stability under a humid environment.
We employ a mesoporous BaSnO3 electron transport layer to satisfy both solar-cell performance and stability as an alternative to conventional Li-doped TiO2. Both BaSnO3 and Li-doped TiO2 show considerable power conversion efficiency exceeding 21% and 20%, respectively, under 10% relative humidity. However, in 40% relative humidity, PSCs using Li-doped TiO2 are dramatically deteriorated within 24 h while PSCs with BaSnO3 exhibit excellent processing stability.
Organic semiconductors are key building blocks for future electronic devices that require unprecedented properties of low-weight, flexibility, and portability. However, the low charge-carrier ...mobility and undesirable processing conditions limit their compatibility with low-cost, flexible, and printable electronics. Here, we present significantly enhanced field-effect mobility (μFET) in semiconducting polymers mixed with boron-doped carbon nanotubes (B-CNTs). In contrast to undoped CNTs, which tend to form undesired aggregates, the B-CNTs exhibit an excellent dispersion in conjugated polymer matrices and improve the charge transport between polymer chains. Consequently, the B-CNT-mixed semiconducting polymers enable the fabrication of high-performance FETs on plastic substrates via a solution process; the μFET of the resulting FETs reaches 7.2 cm2 V–1 s–1, which is the highest value reported for a flexible FET based on a semiconducting polymer. Our approach is applicable to various semiconducting polymers without any additional undesirable processing treatments, indicating its versatility, universality, and potential for high-performance printable electronics.
The past two decades of vigorous interdisciplinary approaches has seen tremendous breakthroughs in both scientific and technological developments of bulk‐heterojunction organic solar cells (OSCs) ...based on nanocomposites of π‐conjugated organic semiconductors. Because of their unique functionalities, the OSC field is expected to enable innovative photovoltaic applications that can be difficult to achieve using traditional inorganic solar cells: OSCs are printable, portable, wearable, disposable, biocompatible, and attachable to curved surfaces. The ultimate objective of this field is to develop cost‐effective, stable, and high‐performance photovoltaic modules fabricated on large‐area flexible plastic substrates via high‐volume/throughput roll‐to‐roll printing processing and thus achieve the practical implementation of OSCs. Recently, intensive research efforts into the development of organic materials, processing techniques, interface engineering, and device architectures have led to a remarkable improvement in power conversion efficiencies, exceeding 11%, which has finally brought OSCs close to commercialization. Current research interests are expanding from academic to industrial viewpoints to improve device stability and compatibility with large‐scale printing processes, which must be addressed to realize viable applications. Here, both academic and industrial issues are reviewed by highlighting historically monumental research results and recent state‐of‐the‐art progress in OSCs. Moreover, perspectives on five core technologies that affect the realization of the practical use of OSCs are presented, including device efficiency, device stability, flexible and transparent electrodes, module designs, and printing techniques.
Bulk‐heterojunction organic solar cells based on solution‐processable organic semiconductors enable completely new functionalities of being printable, portable, wearable, biocompatible, and attachable to any curved surfaces. The recent major advances in device efficiency and stability, flexible transparent electrodes, module design, and printing technologies for their commercialization are reviewed. The existing challenges and perspectives for these five core technologies are discussed.
A new tandem architecture for printable photovoltaics using a versatile organic nanocomposite containing photoactive and interfacial materials is demonstrated. The nanocomposite forms an ideal ...self‐organized recombination layer via a spontaneous vertical phase separation, which yields a simplified tandem structure fabricated with only four component layers and a high tandem efficiency of 10.8%.
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