共查询到18条相似文献,搜索用时 0 毫秒
1.
Andrius Devižis Andrius Gelzinis Jevgenij Chmeliov Matthias Diethelm Laurynas Endriukaitis Daniele Padula Roland Hany 《Advanced functional materials》2021,31(29):2102000
Charge transfer (CT) states play a key role in the functioning of organic solar cells; however, understanding the mechanism by which CT states dissociate efficiently into free charges remain a conceptual challenge. Here, the electric field dependent dynamics of charge generation in planar cyanine/fullerene photovoltaic cells is probed over a wide temperature range using time-resolved Stark effect experiments, transient absorption, and photocurrent measurements. Results indicate that dissociation of thermalized CT states is the rate-limiting step for all temperatures. The dissociation rate strongly depends on the field, but is temperature independent. The results also suggest that the yield of generated charges is temperature independent. Model electrostatic calculations illustrate that specific orientations of the cyanine crystal relative to C60 create a repulsive potential for an electron near the interface that is largely due to the quadrupole moment of the unit cell. In combination with the electron-hole coulomb attraction and the electric field-induced barrier lowering, a high-energy potential barrier forms with a narrow width of a few nanometers. It is proposed that charge separation occurs via a field-dependent electron tunneling mechanism through that barrier, which is temperature independent. The results support a thus far overlooked pathway for CT state dissociation via carrier tunneling. 相似文献
2.
Won‐Ik Jeong Yang Eun Lee Hyun‐Sub Shim Tae‐Min Kim Sei‐Yong Kim Jang‐Joo Kim 《Advanced functional materials》2012,22(14):3089-3094
The bulk‐ionized photoconductivity of C60 is reported as an origin of the bias‐dependent linear change of the photocurrent in copper phthalocyanine (CuPc)/C60 planar heterojunction solar cells, based on the observation of the variation of the bias‐dependent photocurrent on excitation wavelengths and the thickness‐dependent photocurrent of the C60 layer. A theoretical model, which is a combination of the Braun‐Onsager model for the dissociation of excitons at the donor/acceptor interface and the Onsager model for the bulk ionization of excitons in the C60 layer, describes the bias‐dependent photocurrent in the devices very well. The bulk‐ionized photoconductivity of C60 must generally contribute to the photocurrent in organic photovoltaics, since fullerene and fullerene derivatives are widely used in these devices. 相似文献
3.
Alexander Foertig Juliane Kniepert Markus Gluecker Thomas Brenner Vladimir Dyakonov Dieter Neher Carsten Deibel 《Advanced functional materials》2014,24(9):1306-1311
A combination of transient photovoltage (TPV), voltage dependent charge extraction (CE), and time delayed collection field (TDCF) measurements is applied to poly[[4,8‐bis[(2‐ethylhexyl)oxy]benzo[1,2‐b:4,5‐b']dithiophene‐2,6‐diyl] [3‐fluoro‐2‐[(2‐ethylhexyl)carbonyl] thieno[3,4‐b]thiophenediyl]] (PTB7):[6,6]‐phenyl‐C71‐butyric acid (PC71BM) bulk heterojunction solar cells to analyze the limitations of photovoltaic performance. Devices are processed from pure chlorobenzene (CB) solution and a subset is optimized with 1,8‐diiodooctane (DIO) as co‐solvent. The dramatic changes in device performance are discussed with respect to the dominating loss processes. While in the devices processed from CB solution severe geminate and nongeminate recombination is observed, the use of DIO facilitates efficient polaron pair dissociation and minimizes geminate recombination. Thus, from the determined charge carrier decay rate under open circuit conditions and the voltage dependent charge carrier densities n(V), the nongeminate loss current Jloss of the samples with DIO alone enables the reconstruction of the current/voltage (j/V) characteristics across the whole operational voltage range. Geminate and nongeminate losses are considered to describe the j/V response of cells prepared without additive, but lead to a clearly overestimated device performance. The deviation between measured and reconstructed j/V characteristics is attributed to trapped charges in isolated domains of pure fullerene phases. 相似文献
4.
Ilja Vladimirov Sebastian Müller Roelf‐Peter Baumann Thomas Geßner Zahra Molla Souren Grigorian Anna Khler Heinz Bssler Ullrich Pietsch Ralf Thomas Weitz 《Advanced functional materials》2019,29(12)
The fundamental nature of charge transport in highly ordered organic semiconductors is under constant debate. At cryogenic temperatures, effects within the semiconductor such as traps or the interaction of charge carriers with the insulating substrate (dipolar disorder or Fröhlich polarons) are known to limit carrier motion. In comparison, at elevated temperatures, where charge carrier mobility often also decreases as function of temperature, phonon scattering or dynamic disorder are frequently discussed mechanisms, but the exact microscopic cause that limits carrier motion is debated. Here, the mobility in the temperature range between 200 and 420 K as function of carrier density is explored in highly ordered perylene‐diimide from 3 to 9 nm thin films. It is observed that above room temperature increasing the gate electric field or decreasing the semiconducting film thickness leads to a suppression of the charge carrier mobility. Via X‐ray diffraction measurements at various temperatures and electric fields, changes of the thin film structure are excluded as cause for the observed mobility decrease. The experimental findings point toward scattering sites or traps at the semiconductor–dielectric interface, or in the dielectric as limiting factor for carrier mobility, whose role is usually neglected at elevated temperatures. 相似文献
5.
通过分析有机电致发光器件中载流子注入、输运、激子的解离与复合过程,提出了激子解离与复合的理论模型。基于电流连续性方程和Poisson方程,给出了激子复合几率、电流密度及复合效率表达式。研究了外加电压和温度对器件中激子的复合几率及在各种接触条件下外加电压对器件电流和复合效率的影响。结果表明:(1)在一个较宽的注入势垒范围内,复合几率随电场和温度的升高而降低;(2)固定阴极势垒,而阳极势垒由小变大时,器件电流由接触限制向空间电荷限制转变;(3)复合效率随外加电压升高先增加,当电压达一临界值时而陡降,并存在一个最佳的注入势垒值。其计算值与所报道的实验结果相符合。 相似文献
6.
Monomolecular and Bimolecular Recombination of Electron–Hole Pairs at the Interface of a Bilayer Organic Solar Cell 下载免费PDF全文
Tobias Hahn Steffen Tscheuschner Frank‐Julian Kahle Markus Reichenberger Stavros Athanasopoulos Christina Saller Guillermo C. Bazan Thuc‐Quyen Nguyen Peter Strohriegl Heinz Bässler Anna Köhler 《Advanced functional materials》2017,27(1)
While it has been argued that field‐dependent geminate pair recombination (GR) is important, this process is often disregarded when analyzing the recombination kinetics in bulk heterojunction organic solar cells (OSCs). To differentiate between the contributions of GR and nongeminate recombination (NGR) the authors study bilayer OSCs using either a PCDTBT‐type polymer layer with a thickness from 14 to 66 nm or a 60 nm thick p‐DTS(FBTTh2)2 layer as donor material and C60 as acceptor. The authors measure JV‐characteristics as a function of intensity and charge‐extraction‐by‐linearly‐increasing‐voltage‐type hole mobilities. The experiments have been complemented by Monte Carlo simulations. The authors find that fill factor (FF) decreases with increasing donor layer thickness (Lp) even at the lowest light intensities where geminate recombination dominates. The authors interpret this in terms of thickness dependent back diffusion of holes toward their siblings at the donor–acceptor interface that are already beyond the Langevin capture sphere rather than to charge accumulation at the donor–acceptor interface. This effect is absent in the p‐DTS(FBTTh2)2 diode in which the hole mobility is by two orders of magnitude higher. At higher light intensities, NGR occurs as evidenced by the evolution of s‐shape of the JV‐curves and the concomitant additional decrease of the FF with increasing layer thickness. 相似文献
7.
Lin Tan Lei Zhang Xi Jiang Xiaodi Yang Linjun Wang Zhaohui Wang Liqiang Li Wenping Hu Zhigang Shuai Lin Li Daoben Zhu 《Advanced functional materials》2009,19(2):272-276
A novel semiconductor based on annelated β‐trithiophenes is presented, possessing an extraordinary compressed packing mode combining edge‐to‐face π–π interactions and S…S interactions in single crystals, which is favorable for more effective charge transporting. Accordingly, the device incorporating this semiconductor shows remarkably high charge carrier mobility, as high as 0.89 cm2 V?1 s?1, and an on/off ratio of 4.6 × 107 for vacuum‐deposited thin films. 相似文献
8.
Enhancement of n‐Type Organic Field‐Effect Transistor Performances through Surface Doping with Aminosilanes 下载免费PDF全文
Nara Shin Jakob Zessin Min Ho Lee Mike Hambsch Stefan C. B. Mannsfeld 《Advanced functional materials》2018,28(34)
Dopants, i.e., electronically active impurities, are added to organic semiconductor materials to control the material's Fermi level and conductivity, to improve injection at the device contacts, or to fill trap states in the active device layers and interfaces. In contrast to bulk doping as achieved by blending or co‐deposition of dopant and semiconductor, surface doping has a lower propensity to introduce additional traps or scattering centers or to even alter the layer morphology relative to the undoped active material layers. In this study, the electrical effects of a very simple, post‐device‐fabrication surface doping process involving various amine group–containing alkoxysilanes on the performance of organic field‐effect transistors (OFETs) made from the well‐known n‐type materials PTCDI‐C8 and N2200 are researched. It is demonstrated that OFETs doped in such a way generally show enhanced characteristics (up to 10 times mobility increase and a significant reduction in threshold voltage) without any adverse effects on the devices' on/off ratio. It is also shown that the efficiency of the doping process is linked to the number of amine groups. 相似文献
9.
Satria Zulkarnaen Bisri Taishi Takenobu Yohei Yomogida Hidekazu Shimotani Takeshi Yamao Shu Hotta Yoshihiro Iwasa 《Advanced functional materials》2009,19(11):1728-1735
A high‐performance ambipolar light‐emitting transistor (LET) that has high hole and electron mobilities and excellent luminescence characteristics is described. By using this device, a conspicuous light‐confined edge emission and current‐density‐dependent spectral evolution are observed. These findings will result in broader utilization of device potential and they provide a promising route for realizing electrically driven organic lasers. 相似文献
10.
Diketopyrrolopyrrole Organic Thin‐Film Transistors: Impact of Alkyl Substituents and Tolerance of Ethylhexyl Stereoisomers 下载免费PDF全文
Matthias Stolte Sabin‐Lucian Suraru Patricia Diemer Tao He Christian Burschka Ute Zschieschang Hagen Klauk Frank Würthner 《Advanced functional materials》2016,26(41):7415-7422
Bis(thiophen‐2‐yl)‐diketopyrrolopyrrole (DPP) dyes bearing various alkyl substituents at the amide positions (n‐butyl, n‐pentyl, n‐hexyl, n‐heptyl, n‐octyl, 2‐ethylhexyl) and chlorine (Cl), bromine (Br), or cyano (CN) substituents at the thiophene positions have been synthesized and investigated with regard to their molecular and semiconducting properties. Intense absorption, strong fluorescence, and reversible oxidation and reduction processes are common to all of these dyes. Their characterization as organic semiconductors in vacuum‐processed thin‐film transistors reveals p‐channel operation with field‐effect mobilities ranging from 0.01 to 0.7 cm2 V?1 s?1. The highest mobility is found for the DPP dyes bearing the 2‐ethylhexyl substituents, which is surprising, considering that as a result of the chiral substituents, this material is a mixture of (R,R), (S,S), and (R,S) stereoisomers. The high carrier mobility in the films of the DPPs bearing stereoisomerically inhomogeneous ethylhexyl groups is rationalized here by single‐crystal X‐ray diffraction (XRD) analysis in combination with XRD and atomic force microscopy studies on thin films, which reveal the presence of slightly different 2D layer arrangements for the n‐alkyl and the 2‐ethylhexyl derivatives. For the cyano‐substituted DPPs possessing the lowest LUMO levels, ambipolar transport characteristics are observed. 相似文献
11.
12.
Yuefang Wei Yuyan Zhang Yutong Ren Bing Zhang Yi Yuan Jing Zhang Peng Wang 《Advanced functional materials》2023,33(43):2307501
Achieving the desired thermomechanical properties for highly solution-processable organic semiconductors is challenging but crucial for heat tolerance of emerging optoelectronic devices. To this end, the successful synthesis of triphenylene–ethylenedioxythiophene-dimethoxytriphenylamine (TP–ETPA), a star-shaped organic semiconductor, is reported through a direct arylation reaction that involves ETPA, an electron donor, being grafted densely onto TP, which possesses six electron-equivalent functionalization sites. Remarkably, TP–ETPA exhibits significantly improved hole mobility compared to 2,2′,7,7′-tetrakis(N,N-di-p-methoxyphenyl-amine)-9,9′-spirobifluorene (spiro-OMeTAD) at a given hole density, owing to its lower energetic disorder, larger average centroid distance, and smaller reorganization energy. TP–ETPA, with a molecular weight of 2888 Da and lacking flexible chains, demonstrates extraordinary solubility in nonpolar solvents, enabling the formation of dense, pinhole-free films through solution codeposition with an air-doping promoter. By utilizing the p-doped TP–ETPA composite as the hole transport layer, perovskite solar cells with an average power conversion efficiency of 23.4% are successfully fabricated. Notably, these devices display significantly enhanced operational stability and thermal stability at 85 °C. Molecular dynamics simulations reveal that the TP–ETPA-based hole transport layer possesses a high cohesive energy density, resulting in a large elastic modulus and slow diffusion of external species. 相似文献
13.
Hybrid Organic/PbS Quantum Dot Bilayer Photodetector with Low Dark Current and High Detectivity 下载免费PDF全文
Yuanzhi Wei Zhenwei Ren Andong Zhang Peng Mao Hui Li Xinhua Zhong Weiwei Li Shiyong Yang Jizheng Wang 《Advanced functional materials》2018,28(11)
Owing to their ease of fabrication, low cost, and high flexibility, organic materials have attracted great interests in photodetector (PD) applications. However, suffering from large dark current, small photocurrent, low on–off ratio, and low sensitivity, performances of bare organic‐based PDs are not satisfactory. Integrating organic materials with other novel semiconductor materials offers an opportunity to overcome these drawbacks. Here, a lateral hybrid organic/lead sulfide (PbS) quantum dot bilayer PD is designed and fabricated, which significantly suppresses the dark current and enhances the photocurrent, leading to improved light detecting capability. Meanwhile, the bilayer PD can be made on a flexible polyimide substrate. 相似文献
14.
Xiaoyang Du Yi Yuan Lei Zhou Hui Lin Caijun Zheng Junyi Luo Zhenhua Chen Silu Tao Liang‐Sheng Liao 《Advanced functional materials》2020,30(15)
Charge transfer state (CT) plays an important role in exciton diffusion, dissociation, and charge recombination mechanisms. Enhancing the utilization and suppressing the recombination process of CT excitons is a promising way to improve the performance of organic solar cells (OSCs). Here, an effective method is presented via introducing a delayed fluorescence (DF) emitter 3,4‐bis(4‐(diphenylamino)phenyl)acenaphtho[1,2‐b]pyrazine‐8,9‐dicarbonitrile (APDC‐TPDA) in OSCs. The long‐lifetime singlet excitons on APDC‐TPDA can transfer to polymer donors to prolong exciton lifetime, which ensures sufficient time for diffusion and dissociation. Concurrently, the high triplet energy level (T1) of the DF material can also prevent the reverse energy transfer from CT to T1. APDC‐TPDA‐containing ternary OSCs shows a high PCE of 16.96% with a reduced recombination energy loss of 0.46 eV. It is noteworthy that the ternary OSC also exhibits superior storage stability. After 55 days of storage, the PCE of the ternary OSC still retains about 96% of its primitive state. Furthermore, this ternary strategy is efficient and universally applicable to OSCs, and positive results can be obtained in different systems with different DF emitters. These results indicate that the ternary strategy provides a new design idea to realize high performance OSCs. 相似文献
15.
Xin Song Nicola Gasparini Masrur Morshed Nahid Sri Harish Kumar Paleti Cheng Li Weiwei Li Harald Ade Derya Baran 《Advanced functional materials》2019,29(34)
The high crystallinity and ability to harvest near‐infrared photons make diketopyrrolopyrrole (DPP)‐based polymers one of the most promising donors for high performing organic solar cells (OSCs). However, DPP‐based OSC devices still suffer from the trade‐off between energetic loss (Eloss) and maximum external quantum efficiency (EQEmax), which significantly hinders their potential. Thus far, the replacement of fullerenes with small molecule acceptors did not wisdom the performance development of DPP‐donor‐based solar cells due to severe charge recombination issues. In this work, efficient DPP‐based solar cells are reported using low bandgap fused ring electron acceptor, IEICO‐4F. PBDTT‐DPP:IEICO‐4F OSC devices deliver a champion power conversion efficiency of 9.66% with successful interface engineering along with low Eloss of 0.57 eV and a high EQEmax (>70%). 相似文献
16.
An Electron Acceptor with Broad Visible–NIR Absorption and Unique Solid State Packing for As‐Cast High Performance Binary Organic Solar Cells 下载免费PDF全文
Xueliang Shi Xunfan Liao Ke Gao Lijian Zuo Jingde Chen Jingbo Zhao Feng Liu Yiwang Chen Alex K.‐Y. Jen 《Advanced functional materials》2018,28(33)
A novel acceptor–donor–acceptor (A–D–A) type electron acceptor 6TIC‐4F with terthieno[3,2‐b]thiophene (6T) as the core unit is rationally designed and synthesized, which exhibits an extraordinarily narrow bandgap (≈1.24 eV) and strong absorption between 650 and 1000 nm. X‐ray crystallographic analysis reveals that it has unique intermolecular π–π stacking. The solar cells based on the as‐cast poly[(2,6‐(4,8‐bis(5‐(2‐ethylhexyl)thiophen‐2‐yl)‐benzo[1,2‐b:4,5‐b′]dithiophene))‐alt‐(5,5‐(1′,3′‐di‐2‐thienyl‐5′,7′‐bis(2‐ethylhexyl)benzo[1′,2′‐c:4′,5′‐c′]dithiophene‐4,8‐dione))]) (PBDB‐T): 6TIC‐4F binary blends exhibit an excellent power conversion efficiency (PCE) of 11.14% with a high JSC of 23.00 mA cm?2, and a high fill factor of 0.67, which represents one of the best PCE values for low bandgap (Eg < 1.3 eV)–based organic solar cells. 相似文献
17.
Efficient Nondoped Blue Fluorescent Organic Light‐Emitting Diodes (OLEDs) with a High External Quantum Efficiency of 9.4% @ 1000 cd m−2 Based on Phenanthroimidazole−Anthracene Derivative 下载免费PDF全文
Xiangyang Tang Qing Bai Tong Shan Jinyu Li Yu Gao Futong Liu Hui Liu Bing Yang Feng Li Ping Lu 《Advanced functional materials》2018,28(11)
Organic light‐emitting diodes (OLEDs) can promise flexible, light weight, energy conservation, and many other advantages for next‐generation display and lighting applications. However, achieving efficient blue electroluminescence still remains a challenge. Though both phosphorescent and thermally activated delayed fluorescence materials can realize high‐efficiency via effective triplet utilization, they need to be doped into appropriate host materials and often suffer from certain degree of efficiency roll‐off. Therefore, developing efficient blue‐emitting materials suitable for nondoped device with little efficiency roll‐off is of great significance in terms of practical applications. Herein, a phenanthroimidazole?anthracene blue‐emitting material is reported that can attain high efficiency at high luminescence in nondoped OLEDs. The maximum external quantum efficiency (EQE) of nondoped device is 9.44% which is acquired at the luminescence of 1000 cd m?2. The EQE is still as high as 8.09% even the luminescence reaches 10 000 cd m?2. The maximum luminescence is ≈57 000 cd m?2. The electroluminescence (EL) spectrum shows an emission peak of 470 nm and the Commission International de L'Eclairage (CIE) coordinates is (0.14, 0.19) at the voltage of 7 V. To the best of the knowledge, this is among the best results of nondoped blue EL devices. 相似文献
18.
High Efficiency Deep‐Blue Phosphorescent Organic Light‐Emitting Diodes with CIE x,y (≤ 0.15) and Low Efficiency Roll‐Off by Employing a High Triplet Energy Bipolar Host Material 下载免费PDF全文
《Advanced functional materials》2018,28(36)
Recently, bipolar host materials are the most promising candidates for achieving high performance phosphorescent organic light‐emitting diodes (PHOLEDs) in order to maximize recombination efficiency. However, the development of host material with high triplet energy (E T) is still a great challenge to date to overcome the limitations associated with the present PHOLEDs. Herein, a highly efficient donor‐π‐acceptor (D‐π‐A) type bipolar host (4′‐(9H‐carbazol‐9‐yl)‐2,2′‐dimethyl‐[1,1′‐biphenyl]‐4‐yl)diphenylphosphine oxide (m‐CBPPO) comprising of carbazole, 2,2′‐dimethylbiphenyl and diphenylphosphoryl as D‐π‐A unit, respectively, is developed. Interestingly, a high E T of 3.02 eV is observed for m‐CBPPO due to highly twisted conformation. Furthermore, the new host material is incorporated in PHOLEDs as emissive layer with a new carbene type Ir(cb)3 material as a deep‐blue emitter. The optimized devices show an excellent external quantum efficiency (EQE) of 24.8% with a notable Commission internationale de l'éclairage (x, y) ≤ 0.15, (0.136, 0.138) and high electroluminescence performance with extremely low efficiency roll‐off. Overall, the above EQE is the highest reported for deep‐blue PHOLEDs with very low efficiency roll‐off and also indicate the importance of appropriate host for the development of high performance deep‐blue PHOLEDs. 相似文献