Charge Transfer States in D-A Excitonic Solar Cells: Photophysical Characterization and Loss Mechanisms for Charge Generation

D-A 激子太阳能电池中的电荷转移态：电荷产生的光物理表征和损失机制

• 批准号: EP/I006656/1
• 负责人: Fernando Dias
• 金额: $ 12.92万
• 依托单位: Durham University
• 依托单位国家: 英国
• 项目类别: Research Grant
• 财政年份: 2011
• 资助国家: 英国
• 起止时间: 2011 至 无数据
• 项目状态: 已结题
• 来源: https://gtr.ukri.org/projects?ref=EP%2FI006656%2F1
• 关键词: Charge; Transfer; States; Excitonic; Solar

Alternative energy sources are in great demand to support the economic growth of our society. During the past decades the world has been assaulted by the idea of a possible exhaustion of our fossil fuel supply in a relative short period of time, dramatically increasing energy costs as it becomes more and more scarce. The way to face this problem is obviously to look for environment friendly energy sources that satisfy the criteria of being i) cheap, ii) environmentally benign and iii) inexhaustible. Among the ones that satisfy the criteria is the use of sunlight to produce energy by the photovoltaic effect.Recently much attention has been focused on organic, polymeric or hybrid systems for photovoltaic operation. Such solar cells need to be cheap and easy to produce for practical applications. In addition, questions of energy conversion efficiency and long-term stability need to be addressed. Two distinct, but complementary, methodologies have emerged; mesoscopic dye sensitized (DSC) and bulk organic (or polymeric) heterojunction (BHJ) solar cells.In the BHJ configuration, a mixture of a conjugated polymer (donor) and charge acceptor, usually a fullerene derivative, are sandwiched between two metallic electrodes, one of which is transparent. This architecture has the advantage of giving the possibility of process and assemble the active layer using a single step from solution, and make use of classical printing techniques on different types of substrates, avoiding high temperatures and more expensive deposition methods.Organic solar cells differ from their inorganic counterparts by producing bound electron-hole pairs (excitons) upon light absorption; these excitons, as a result of the low dielectric constants of the active medium, show a considerable electron-hole binding energy, around 0.4 eV, and as a consequence, exciton dissociation occurs only at the interface between two materials of different electron affinities, working as electron donor (D) and the electron acceptor (A), which yield a driving force for charge separation.Understanding the fundamental electronic interactions between the D and A materials as well as the role of the composite film morphology, device architecture and processing conditions, is crucial to achieve high efficiencies. Over the last few years progress has been mostly achieved through the understanding of the importance of the active layer morphology, especially the type of solvent used, polymer regioregularity and film annealing conditions to the device final performance.In the proposed research, several electron donor and acceptor materials will be investigated in order to unravel the processes that control the formation and recombination of free charge carriers in organic photovoltaic devices. A particular focus of the research will be the investigation of conjugated materials containing heavy atom complexes, which give rise to an intrinsic mechanism that promotes the formation of triplet excitons. This very rapidly and efficiently converts all polymer singlets into polymer triplets that can be used as electron donors in photovoltaic operation. A detailed investigation of these materials as donor materials in BHJ solar cells is still lacking, and the concept of using long lived triplet excitons in charge generation deserves further attention, particularly in order to clarify the effect of the increasing mixing of singlet and triplet states on the energy of the CT state and geminate back electron transfer.

为了支持我们社会的经济增长，对替代能源的需求很大。在过去的几十年里，我们的化石燃料供应可能在相对较短的时间内耗尽，随着能源变得越来越稀缺，能源成本急剧上升，这一想法一直困扰着世界。面对这个问题的方法显然是寻找满足以下标准的环境友好型能源：1)便宜，2)环保，3)取之不尽用之不竭。其中符合标准的是利用太阳光通过光伏效应产生能量。近年来，有机、聚合物或混合系统的光伏发电备受关注。为了实际应用，这种太阳能电池需要便宜且易于生产。此外，还需要解决能源转换效率和长期稳定的问题。出现了两种不同但互补的方法；介观染料敏化（DSC）和大块有机（或聚合物）异质结（BHJ）太阳能电池。在BHJ结构中，共轭聚合物（施主）和电荷受体（通常是富勒烯衍生物）的混合物夹在两个金属电极之间，其中一个是透明的。这种结构的优点是，可以从溶液中一步完成活性层的加工和组装，并在不同类型的基板上使用传统的印刷技术，避免了高温和更昂贵的沉积方法。有机太阳能电池与无机太阳能电池的不同之处在于光吸收时产生束缚的电子-空穴对（激子）；由于活性介质的介电常数较低，这些激子显示出相当大的电子-空穴结合能，约为0.4 eV，因此，激子解离只发生在两种电子亲和度不同的材料之间的界面上，作为电子供体(D)和电子受体(a)，这产生了电荷分离的驱动力。了解D和A材料之间的基本电子相互作用，以及复合膜形态，器件结构和加工条件的作用，对于实现高效率至关重要。在过去的几年里，通过理解活性层形态的重要性，特别是使用的溶剂类型，聚合物区域规则性和薄膜退火条件对器件最终性能的重要性，取得了很大的进展。在本研究中，将研究几种电子供体和受体材料，以揭示控制有机光伏器件中自由载流子形成和重组的过程。研究的一个特别重点将是研究含有重原子配合物的共轭材料，它产生了促进三重态激子形成的内在机制。这非常迅速和有效地将所有的聚合物单态转化为聚合物三态，可以用作光伏操作中的电子供体。对这些材料作为BHJ太阳能电池供体材料的详细研究仍然缺乏，使用长寿命三重态激子产生电荷的概念值得进一步关注，特别是为了阐明单重态和三重态混合增加对CT态能量和双回电子转移的影响。

项目成果

Inter/Intrachain Interactions Behind the Formation of Charge Transfer States in Polyspirobifluorene: A Case Study for Complex Excited-State Dynamics in Different Polarity Index Solvents

聚螺二芴中电荷转移态形成背后的链间/链内相互作用：不同极性指数溶剂中复杂激发态动力学的案例研究

• DOI: 10.1021/jp512467g
• 发表时间: 2015
• 期刊: The Journal of Physical Chemistry C
• 作者: Aydemir M

High efficiency OLEDs based on anthracene derivatives: The impact of electron donating and withdrawing group on the performance of OLED

• DOI: 10.1016/j.orgel.2015.11.026
• 发表时间: 2016-03-01
• 期刊: ORGANIC ELECTRONICS
• 影响因子: 3.2
• 作者: Aydemir, Murat;Haykir, Gulcin;Monkman, Andrew P.
• 通讯作者: Monkman, Andrew P.

Highly Efficient TADF OLEDs: How the Emitter-Host Interaction Controls Both the Excited State Species and Electrical Properties of the Devices to Achieve Near 100% Triplet Harvesting and High Efficiency

• DOI: 10.1002/adfm.201400948
• 发表时间: 2014-10-22
• 期刊: ADVANCED FUNCTIONAL MATERIALS
• 影响因子: 19
• 作者: Jankus, Vygintas;Data, Przemyslaw;Monkman, Andrew P.
• 通讯作者: Monkman, Andrew P.

The Role of Local Triplet Excited States and D-A Relative Orientation in Thermally Activated Delayed Fluorescence: Photophysics and Devices.

• DOI: 10.1002/advs.201600080
• 发表时间: 2016-12
• 期刊: ADVANCED SCIENCE
• 影响因子: 15.1
• 作者: Dias, Fernando B.;Santos, Jose;Graves, David R.;Data, Przemyslaw;Nobuyasu, Roberto S.;Fox, Mark A.;Batsanov, Andrei S.;Palmeira, Tiago;Berberan-Santos, Mrio N.;Bryce, Martin R.;Monkman, Andrew P.
• 通讯作者: Monkman, Andrew P.

Deep Blue Exciplex Organic Light-Emitting Diodes with Enhanced Efficiency; P-type or E-type Triplet Conversion to Singlet Excitons?

• DOI: 10.1002/adma.201203615
• 发表时间: 2013-03-13
• 期刊: ADVANCED MATERIALS
• 影响因子: 29.4
• 作者: Jankus, Vygintas;Chiang, Chien-Jung;Monkman, Andrew P.
• 通讯作者: Monkman, Andrew P.