Current-based deep level transient spectroscopy was used to study trap states in poly(3- hexylthiophene-2,5-diyl) (P3HT), [6,6]-phenyl-C61 butyric acid methyl ester (PCBM) and P3HT:PCBM blend. The obtained spectra showed traps of 87 meV activation energy in pure P3HT and 21 meV for PCBM. The blend shows a complex emission rate spectrum consisting of several different emission rate bands in the range of (0.1-30) s^-1, yielding activation energies between about 30 meV and 160 meV.
Recombination losses contribute to reduce $J_{SC}$, $V_{OC}$ and the fill factor of organic solar cells. Recent advances in non-fullerene organic photovoltaics have shown, nonetheless, that efficient charge generation can occur under small energetic driving forces ($ΔE_{DA}$) and low recombination losses. To shed light on this issue, we set up a coarse-grained open quantum mechanical model for investigating the charge generation dynamics subject to various energy loss mechanisms. The influence of energetic driving force, Coulomb interaction, vibrational disorder, geminate recombination, temper…
Linking the highly complex morphology of organic photovoltaic (OPV) thin films to their charge transport properties is critical for achieving high performance material system that serves as a cost-efficient approach for energy harvesting. In this paper, a novel unsupervised feature engineering framework is developed and used to establish reduced-order structure-property linkages for OPV films. This framework takes advantage of digital image processing algorithms to identify the salient material features of OPVs undergoing the charge transport phenomenon. These material states are then used to …
Energy level diagrams in organic electronic devices play a crucial role in device performance and interpretation of device physics. In the case of organic solar cells, it has become routine to estimate the photovoltaic gap of the donor:acceptor blend using the energy values measured on the individual blend components, resulting in a poor agreement with the corresponding open-circuit voltage of the device. To address this issue, we developed a method that allows a direct visualisation of the vertical energetic landscape in the blend, obtained by combining ultraviolet photoemission spectroscopy …
Enhancement of photovoltaic efficiency by insertion of a polyoxometalate layer at the anode of an organic solar cell
在这篇文章中，Wells-Dawson聚氧乙烯醚K6[P2 W 18 O 62]生长作为铟锡氧化物和聚（3-己基噻吩）（P3 HT）和[6，6]-苯基-C61-丁酸甲酯（PCBM）的体异质结之间的界面层。POM层的结构取决于厚度，并显示出高度各向异性的表面组织。薄膜的特征在于原子力显微镜和X射线光电子能谱学（XPS），以深入了解其宏观组织，更好地了解其电子性能。然后，将它们放置在P3 HT：PCBM有机太阳能电池的阳极界面上，并在光学工作台上进行表征。讨论了在有机光电池的阳极界面处的聚氧乙烯酸盐的益处方面的光伏效率。
Electron energy-loss spectroscopy (EELS) is a powerful tool for imaging chemical variations at the nanoscale. Here, we investigate a polymer/organic small molecule-blend used as absorber layer in an organic solar cell and employ EELS for distinguishing polymer donor and small molecule acceptor domains in the nanostructured blend based on elemental maps of light elements, such as nitrogen, sulfur or fluorine. Especially for beam sensitive samples, the electron dose needs to be limited, therefore optimized acquisition and data processing strategies are required. We compare data acquired on a pos…
Organic heterojunction solar cells are analyzed within a minimal model that includes the essential physical features of such systems. The dynamical properties of this model, calculated using a master equation approach, account for the qualitative behavior of such systems. The model yields explicit results for current-voltage behavior as well as performance characteristics expressed in terms of the thermodynamic efficiency as well as the power conversion efficiency at maximum power, making it possible to evaluate the optimal setup for this device model.
First-principles investigation of organic photovoltaic materials C$_{60}$, C$_{70}$, [C$_{60}$]PCBM, and bis-[C$_{60}$]PCBM using a many-body $G_0W_0$-Lanczos approach
We theoretically investigate an exciton transfer process in a donor domain of organic photovoltaic cells focusing on the roles of local and nonlocal electron-phonon interactions. Our model consists of a three-level system described by the Holstein-Peierls Hamiltonian coupled to multiple heat baths for local and nonlocal molecular modes characterized by Brownian spectral distribution functions. We chose tetracene as a reference donor molecule, where the spectral distribution functions of the local and nonlocal modes exist. We then employ the reduced hierarchy equations of motion (HEOM) approach…
In organic photovoltaics, charges can separate efficiently even if their Coulomb attraction is an order of magnitude greater than the available thermal energy. Delocalization has been suggested to explain this fact, because it could increase the initial separation of charges in the charge-transfer (CT) state, reducing their attraction. However, understanding the mechanism requires a kinetic model of delocalized charge separation, which has proven difficult because it involves tracking the correlated quantum-mechanical motion of the electron and the hole in large simulation boxes required for d…
Triplet excited states in organic semiconductor materials and devices are notoriously difficult to detect and study with established spectroscopic methods. Yet, they are a crucial intermediate step in next-generation organic light emitting diodes (OLED) that employ thermally activated delayed fluorescence (TADF) to upconvert non-emissive triplets to emissive singlet states. In organic photovoltaic (OPV) devices, however, triplets are an efficiency-limiting exciton loss channel and are also involved in device degradation. Here, we introduce an innovative spin-sensitive method to study triplet s…
Delocalisation explains efficient transport and charge generation in neat Y6 organic photovoltaics
University of Sydney（悉尼大学）；Victoria University of Wellington（惠灵顿维多利亚大学）；MacDiarmid Institute for Advanced Materials and Nanotechnology（先进材料与纳米技术麦克迪亚米德研究所）；The Dodd-Walls Centre for Photonic and Quantum Technologies（光子与量子技术多兹中心）；Institute for Integrated Cell-Material Sciences (iCeMS)（细胞材料综合科学研究所）
We present a neutron spectroscopy based method to study quantitatively the partial miscibility and phase behaviour of an organic photovoltaic active layer made of conjugated polymer:small molecule blends, presently illustrated with the regio-random poly(3-hexylthiophene-2,5-diyl) and fullerene [6,6]-Phenyl C$_{61}$ butyric acid methyl ester (RRa-P3HT:PCBM) system. We perform both inelastic neutron scattering and quasi-elastic neutron scattering measurements to study the structural dynamics of blends of different compositions enabling us to resolve the phase behaviour. The difference of neutron…
Physical-chemical Approach for the Impact of Modifying Molecular Bridges of TPA-Based Systems to Improve the Photovoltaic Properties of Organic Solar Cells
First-principles GW calculations for fullerenes, porphyrins, phtalocyanine, and other molecules of interest for organic photovoltaic applications
我们评估的性能从头计算的电离能和HOMO-LUMO间隙的13个气相分子的兴趣为有机电子和光伏应用，包括C60富勒烯，并五苯，自由基卟啉和酞菁，PTCDA，和标准单体，如噻吩，芴，苯并噻唑或噻二唑。标准的G 0 W 0计算，即从本征态得到的局部或半局部泛函，显着提高电离能和带隙相比，密度泛函理论Kohn-Sham的结果，但计算的准粒子值仍然太小，作为过屏蔽的结果。从类Hartree-Fock特征值出发，得到了更好的结果，相当于对特征值进行了自洽，与实验结果相比，精度为2~4%.我们的计算是基于一个有效的高斯基础上实现GW的动态筛选，通过轮廓变形技术的显式治疗。
In this paper we present CTRAMER (Charge Transfer RAtes from Molecular dynamics, Electronic structure, and Rate theory), an open source software package for calculating interfacial charge transfer (CT) rate constants in organic photovoltaic (OPV) materials based on ab initio calculations and molecular dynamics simulations. The software is based on identifying representative donor acceptor geometries within interfacial structures obtained from molecular dynamics simulation of donor acceptor blends and calculating the corresponding Fermi s golden rule CT rate constants within the framework of th…
We report the application of a coordination polymer semiconductor, tin(II) thiocyanate [Sn(SCN)$_2$] as an ultrathin anode interlayer in organic photovoltaics (OPVs). Sub-10 nm layers of Sn(SCN)$_2$ with high smoothness and excellent transparency having an optical band gap of 3.9 eV were deposited from an alcohol-based solution at room temperature without post-deposition annealing. Inserting Sn(SCN)$_2$ as an anode interlayer in polymer:fullerene OPVs drastically reduces the recombination loss due to the exciton-blocking energy levels of Sn(SCN)$_2$. At the optimum thickness of 7 nm, an averag…
High-Throughput Photovoltaic Screening and Spacer-Dependent Shift Current in Two-Dimensional Hybrid Perovskites
Humboldt-Universität zu Berlin（柏林洪堡大学）；Institute of Materials Science, Technische Universität Darmstadt（达姆施塔特工业大学材料科学研究所）；North University of China（中北大学）；State Key Laboratory of Extreme Environment Optoelectronic Dynamic Measurement Technology and Instrument（极端环境光电动态测量技术与仪器国家重点实验室）；Materials Genome Institute, Shanghai University（上海大学材料基因组研究院）；Fujian Science & Technology Innovation Laboratory for Optoelectronic Information of China（福建省光电信息科技创新实验室）
