高性能聚合物光伏材料的设计与应用

高性能聚合物光伏材料对于推动聚合物太阳能电池领域的发展具有十分重要的作用.随着研究的深入,聚合物光伏材料从早期的聚噻吩体系逐步发展到具有推拉电子作用的给体-受体(D-A)交替共聚物,其相应的器件光伏效率也从最初的1%左右提升到如今超过11%.近十年来,种类繁多的给受体单元被开发并应用于聚合物材料的构建中,其中基于苯并二噻吩(BDT)单元的聚合物材料因为具有良好的光伏性能,得到了十分广泛的应用.近年来,非富勒烯受体的迅速发展给聚合物太阳能电池的研究注入了新的活力,BDT类聚合物在基于非富勒烯受体的聚合物太阳能电池中也展现出重要的作用,已经获得了超过11%的光电转化效率.本文简要介绍了我们在高性能聚合物光伏材料的设计与应用中的相关工作,主要分为聚噻吩和苯并二噻吩材料的设计与应用、活性层形貌调控以及非富勒烯聚合物太阳能电池的相关研究.     

含噻吩窄带隙共轭聚合物类太阳能电池材料的研究进展

含噻吩的窄带隙共轭聚合物类太阳能电池材料因其良好的稳定性和可加工性,已成为新型太阳能电池的研究热点。本论文主要介绍了用于太阳能电池的窄带隙共轭聚合物研究进展,按其结构特征分为烷基/烷氧基取代聚噻吩、含苯基聚噻吩、基于噻吩并吡嗪的共聚物、基于噻吩并噻唑的共聚物、基于噻吩并吩噻嗪的共聚物、基于烷基芴的共聚物以及其它种类的窄带隙的共轭聚合物,并对它们的结构特点、光学带隙、合成方法进行了归纳与总结。本文最后简要介绍了该研究领域目前所面临的一些问题,同时讨论了该类材料在此领域今后的发展趋势。     

主链含噻唑单元的新型聚噻吩衍生物的合成与光伏性能

聚噻吩(PT)衍生物由于简单易合成和较好的光电性能,被广泛运用于有机太阳能电池(OSCs)中,但PT较高的能级限制了其在非富勒烯类OSCs的应用。为了降低PT的能级结构,本研究将噻唑单元引入到聚噻吩主链中,设计并合成了新型聚合物给体材料PBTzCl-T。通过紫外-可见吸收光谱、电化学循环伏安法及密度泛函理论(DFT)计算等对聚合物的结构、光学和电学性能进行了表征,并对制备的光伏器件进行了光电性质研究。结果表明：噻唑的引入能够有效降低聚合物的HOMO和LUMO能级,从而提高光伏器件的开路电压。PBTzCl-T在不同溶剂中表现出不同的预聚集行为,进而影响聚合物给受体界面处的电荷转移能力和活性层形貌,导致光伏器件的短路电流和填充因子变化。     

基于一种新型聚噻吩衍生物为给体的非富勒烯聚合物太阳能电池（英文）

在各种共轭聚合物给体材料中,以聚3-己基噻吩为代表的聚噻吩衍生物因其结构简单、易制备以及良好的空穴传输性能,在富勒烯衍生物为受体材料的聚合物太阳能电池体系中一直是研究重点之一。但是在近年来发展迅速的稠环小分子非富勒烯体系中的相关研究较少。在本工作中,我们通过在噻吩侧链引入烷硫基和氟取代基,设计合成了一种新型的聚噻吩衍生物给体PBSBT-2F;并对其吸收光谱、分子能级、传输性能以及光伏性能进行研究。基于PBSBT-2F:ITIC的聚合物太阳能电池取得6.7%的能量转换效率,其中开路电压为0.75 V,短路电流为13.5 mA·cm~(-2),填充因子为66.6%。结果表明:PBSBT-2F在非富勒烯体系中有很大的应用潜力。     

基于苯并二噻吩的D-A型窄带隙共轭聚合物在太阳能电池中的应用

近年来为获得有机聚合物太阳能电池更高的能量转换效率,越来越多的活性层材料被设计合成出来,尤其是给体材料。其中,基于给体单元苯并二噻吩(BDT)的D-A型窄带隙共轭聚合物更是多次刷新了有机聚合物太阳能电池效率的最高记录,目前达10.6%。本文探讨了基于苯并二噻吩的D-A型窄带隙共轭聚合物材料结构及其应用在太阳能电池中的性能参数关系,从提高开路电压、短路电流和填充因子三个方面总结出了提高基于BDT共轭聚合物太阳能电池能量转换效率的方法。     

含萘并二噻吩小分子受体材料的带隙调控及其在非富勒烯太阳能电池中的应用（英文）

与富勒烯受体材料相比,非富勒烯受体材料具有更强光吸收、可调的带隙和前沿电子轨道能级等优点。本工作中,我们将报道新型含萘并二噻吩小分子受体材料的设计与合成。该材料的吸电子端基与稠环核之间含有一个噻吩桥,因此与不含噻吩桥的同类受体材料相比,该分子(DTNIT)具有更窄的带隙,能与经典的宽带隙聚合物给体PBDB-T实现更好的吸收互补。基于PBDB-T:DTNIT的聚合物太阳能电池实现了0.91 V的开路电压、增大的短路电流(14.42 mA?cm~(-2)),以及7.05%的光电转换效率。该光电转换效率接近于基于PBDB-T:PC71BM的倒置聚合物太阳能电池的效率(7.12%)。该工作不仅报道了一个新型高效非富勒烯受体的合成方法,同时提供了一种非富勒烯受体材料的能级调控策略。     

偶氮噻吩-富勒烯星状化合物的合成与性能研究

利用2—[4—(N—乙基—N—6—羟己基)氨基苯偶氮基]—3—氰基—5—甲酰基噻吩(1)和N—甲基甘氨酸产生的亚胺叶立德与富勒烯反应，合成了含富勒烯的偶氮噻吩化合物(2)，2再与1，3，5-苯三甲酰氯进行取代反应生成了一类以苯为核心、偶氮噻吩为连接桥、三个富勒烯(C50)为电子受体端基的星状化合物3。制备了单层太阳能电池器件(ITO／化合物3／Al)，其单色光光电转换效率(IPCE)约为2．5％。     

聚合物太阳电池光伏材料

聚合物太阳电池由共轭聚合物给体和可溶性富勒烯衍生物受体的共混膜夹在ITO透光电极和金属电极之间所组成,具有结构简单、成本低、重量轻和可制成柔性器件等突出优点,近年来受到广泛关注。聚合物太阳电池中的给体和受体光伏材料是决定器件性能的关键。本文综述了共轭聚合物给体和富勒烯受体光伏材料的最新研究进展,对共轭聚合物受体材料和给体-受体双缆型共轭聚合物光伏材料的研究进展也进行了简要介绍。在共轭聚合物给体材料中对聚噻吩衍生物以及含有苯并噻二唑的窄带隙D-A共聚物进行了重点介绍。     

含噻吩[2,3-b]并噻吩-吡咯[3,4-c]并吡咯二酮结构单元聚合物的合成及其在太阳能电池中的应用研究

设计并合成了一种交叉共轭的(cross-conjugated)缺电子型聚合物单体——二溴代噻吩[2,3-b]并噻吩-吡咯[3,4-c]并吡咯(DPPTTZ)二酮,并将其分别与噻吩(T)、硒吩(Se)和N-甲基吡咯(Py)的双锡试剂进行共聚反应,获得了一类新的供体-受体(D-A)型共轭聚合物光电材料.这类材料分子的最高占有轨道(HOMO)能级较低,因此其光电器件具有较高的开路电压(Voc),稳定性好.此外,它们在紫外-可见光区有较宽的吸收,最大吸收位于波长620 nm附近;能带隙(band gap)小,分别为1.86 e V(p DPPTTZ-T)、1.83 e V(p DPPTTZ-Se)和1.85 e V(p DPPTTZ-Py).器件初步测试结果表明,上述聚合物与PC71BM组成的本体异质结聚合物太阳能电池Voc在0.68~0.81 V之间,能量转化效率(PCE)最高达3.05%(p DPPTTZ-T).     

聚3-己基噻吩：非富勒烯太阳能电池中的量子效率损失和电压损失

聚3-己基噻吩(P3HT)以其合成工艺简单、成本低廉的优势,成为有机光伏领域中最具吸引力的电子给体材料之一。然而,目前P3HT: 非富勒烯太阳能电池的光伏性能仍然较差。在本工作中,我们证明了与P3HT: 富勒烯太阳能电池相比,较快的电荷转移态的非辐射衰减速率(K_nr)是导致P3HT: 非富勒烯太阳能电池中较低的量子效率和较高的电压损失的原因。然后,我们研究了基于非富勒烯受体ZY-4Cl的太阳能电池的工作机理。研究结果表明与P3HT: 非富勒烯体系相比,P3HT: ZY-4Cl中K_nr的降低改善了器件的量子效率,同时降低了电压损失。K_nr降低的原因可以部分归因于电荷转移态能量的增加。此外,给体分子和受体分子之间的距离(DA间距)的增大也是K_nr减少的重要原因。因此,我们得出结论：为了提高P3HT太阳能电池的性能,需进一步降低器件的K_nr,这可通过增加活性层中的DA间距来实现。     

Manipulating active layer morphology of molecular donor/polymer acceptor based organic solar cells through ternary blends

The development of molecular donor/polymer acceptor blend(MD/PA)-type organic solar cells(OSCs) lags far behind other type OSCs. It is due to the large-size phase separation morphology of MD/PAblend, which results from the high crystallinity of molecular donors. In this article, to suppress the crystallinity of molecular donors, we use ternary blends to develop OSCs based on one polymer acceptor(P-BNBP-f BT) and two molecular donors(DR3 TBDTT and BTR) with similar chemical structures.The ternary OSC exhibits a power conversion efficiency(PCE) of 4.85%, which is higher than those of the binary OSCs(PCE=3.60% or 3.86%). To our best knowledge, it is the first report of ternary MD/PA-type OSCs and this PCE is among the highest for MD/PA-type OSCs reported so far. Compared with the binary blends, the ternary blend exhibits decreased crystalline size and improved face-on orientation of the donors. As a result, the ternary blend exhibits improved and balanced charge mobilities, suppressed charge recombination and increased donor/acceptor interfacial areas, which leads to the higher shortcircuit current density. These results suggest that using ternary blend is an effective strategy to manipulate active layer morphology and enhance photovoltaic performance of MD/PA-type OSCs.     

Fullerene derivative acceptors for high performance polymer solar cells

Polymer solar cells (PSCs) are composed of a blend film of a conjugated polymer donor and a soluble fullerene derivative acceptor sandwiched between a PEDOT?:?PSS coated ITO positive electrode and a low workfunction metal negative electrode. The conjugated polymer donor and the fullerene derivative acceptor are the key photovoltaic materials for high performance PSCs. For the acceptors, although [6,6]-phenyl-C(61)-butyric acid methyl ester (PC(60)BM) and its corresponding C(70) derivative PC(70)BM are dominantly used as the acceptors in PSC at present, several series of new fullerene derivatives with higher-lying LUMO energy level and better solubility were reported in recent years for further improving the power conversion efficiency of the PSCs. In this perspective paper, we reviewed the recent research progress on the new fullerene derivative acceptors, including various PC(60)BM-like C(60) derivatives, PC(60)BM bisadduct, PC(70)BM bisadduct, indene-C(60) bisadduct and indene-C(70) bisadduct, trimetallic nitride endohedral fullerenes and other C(60) derivatives with multi side chains. The synthesis and physicochemical properties of PC(60)BM and PC(70)BM were also introduced considering the importance of the two fullerene acceptors.     

15.4% Efficiency all-polymer solar cells

We report all-polymer solar cells(All-PSCs) with record-high power conversion efficiency(PCE) through tuning the molecular weights of the polymer donor(PBDB-T) to form optimal active layer morphology. By combining the polymer donors with a newly reported polymer acceptor(PJ1), an unprecedented high PCE of 15.4% and fill factor over 75% were achieved for the AllPSCs with the medium molecular weight polymer donor(PBDB-T_(MW)), which is the highest value for All-PSCs reported so far.Detailed morphology investigation revealed that the proper phase separation in the PBDB-T_(MW):PJ1 blend should account for the superior device performance as PBDB-T_(MW) exhibits appropriate miscibility with the polymer acceptor PJ1. These results demonstrated that the device performance of All-PSCs could be fully comparable to that of small molecular acceptor-based PSCs. The formation of optimized morphology via precise control of molecular weights of polymer donors and acceptors is crucial to achieve this goal.     

Enhanced Charge Transfer,Transport and Photovoltaic Efficiency in All‐Polymer Organic Solar Cells by Polymer Backbone Fluorination

We successfully designed and synthesized two BDT‐BT‐T (BDT=benzo[1,2‐b:4,5‐b']dithiophene, BT‐T=4,7‐dithien‐2‐yl‐2,1,3‐benzothiadiazole) based polymers as the electron donor for application in all‐polymer solar cells (all‐PSCs). By adopting N2200 as the electron acceptor, we systematically investigated the impact of fluorination on the charge transfer, transport, blend morphology and photovoltaic properties of the relevant all‐PSCs. A best power conversion efficiency (PCE) of 3.4% was obtained for fluorinated PT‐BT2F/N2200 (BT2F=difluorobenzo[c][1,2,5]thiadiazole) all‐PSCs in comparison with that of 2.7% in non‐fluorinated PT‐BT/N2200 (BT=benzothiadiazole) based device. Herein, all‐polymers blends adopting either non‐fluorinated PT‐BT or fluorinated PT‐BT2F exhibit similar morphology features. In depth optical spectrum measurements demonstrate that molecular fluorination can further enhance charge transfer between donor and acceptor polymer. Moreover, all‐polymer blends exhibit improved hole mobilities and more balanced carriers transport when adopting fluorinated donor polymer PT‐BT2F. Therefore, although the PCE is relatively low, our findings may become important in understanding how subtle changes in molecular structure impact relevant optoelectronic properties and further improve the performance of all‐PSCSs.     

Effect of side‐chain positions on morphology and photovoltaic properties of phenazine‐based donor–acceptor copolymers

Two phenazine donor–acceptor‐conjugated copolymers (P1 and P2) with the same polymer backbone but different anchoring positions of alkoxy chain on the phenazine unit were investigated to identify the effect of changing the position of alkoxy chains on their optical, electrochemical, blend film morphology, and photovoltaic properties. Although the optical absorption and frontier orbital energy levels were insensitive to the position of alkoxy chains, the film morphologies and photovoltaic performances changed significantly. P1/PC₇₁BM blend film showed the formation of phase separation with large coarse aggregates, whereas P2/PC₇₁BM blend film was homogeneous and smooth. Accordingly, power conversion efficiency (PCE) of photovoltaic devices increased from 1.50% for P1 to 2.54% for P2. In addition, the PCE of the polymer solar cell based on P2/PC₇₁BM blend film could be further improved to 3.49% by using solvent vapor annealing treatment. These results clearly revealed that tuning the side‐chain position could be an effective way to adjust the morphology of the active layer and the efficiency of the photovoltaic device. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2013, 51, 2910–2918     

Bulk heterojunction polymer solar cells based on binary and ternary blend systems

Polymer solar cells (PSCs) were fabricated using a ternary blend film consisting two conjugated polymers and a soluble fullerene derivative as the donor and acceptor materials, respectively. And, to compare ternary blend system, the single‐component copolymers consisting of the repeating units of each of the copolymers, used in ternary blend solar cells, were designed and synthesized for use as the electron donor materials in binary blend solar cells. We systematically investigated the field‐effect carrier mobilities and the optical, electrochemical, and photovoltaic properties of the copolymers. Under optimized conditions, the binary blend polymer systems showed power conversion efficiencies (PCEs) for the PSCs in the range 3.87–4.16% under AM 1.5 illumination (100 mW cm^?2). All polymers exhibited similar PCEs that did not depend on the ratio of repeating units. The binary blend solar cell containing a single‐component copolymer as the electron donor material performed better than the ternary blend solar cell in this work. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011     

非富勒烯聚合物太阳电池研究进展

综述了以p-型共轭聚合物为给体、n-型有机半导体为受体的非富勒烯聚合物太阳电池光伏材料最新研究进展,包括n-型共轭聚合物和可溶液加工小分子n-型有机半导体(n-OS)受体光伏材料,以及与之匹配的p-型共轭聚合物给体光伏材料.介绍的n-型共轭聚合物受体光伏材料包括基于苝酰亚胺(BDI)、萘酰亚胺(NDI)以及新型硼氮键连受体单元的D-A共聚物受体光伏材料,目前基于聚合物给体(J51)和聚合物受体(N2200)的全聚合物太阳电池的能量转换效率最高达到8.26%.n-OS小分子受体光伏材料包括基于BDI和NDI单元的有机分子、基于稠环中心给体单元的A-D-A型窄带隙有机小分子受体材料等.给体光伏材料包括基于齐聚噻吩和苯并二噻吩(BDT)给体单元的D-A共聚物,重点介绍与窄带隙A-D-A结构小分子受体吸收互补的、基于噻吩取代BDT单元的中间带隙二维共轭聚合物给体光伏材料.使用中间带隙的p-型共轭聚合物为给体、窄带隙A-D-A结构有机小分子为受体的非富勒烯聚合物太阳电池能量转换效率已经突破12%,展示了光明的前景.最后对非富勒烯聚合物太阳电池将来的发展进行了展望.     

Synthesis of D-A copolymers based on thiadiazole and thiazolothiazole acceptor units and their applications in ternary polymer solar cells

We have designed and synthesized two wide bandgap new donor-acceptor (D-A) copolymers consisting of the same alkylthiazole-substituted benzo[1,2-b;4,5-b′]dithiophene (BDTTz) donor unit and but different acceptor units, i.e., thiazolo[5,4-d]thiazole (TT_Z) ( P122 ) and 1,3,-4 thiadiazole (TDz) ( P123 ) and investigated their optical and electrochemical properties. We have employed these copolymers as donor and fullerene (PC ₇₁ BM) and narrow bandgap non-fullerene (Y6) as acceptor, to fabricate binary and ternary bulk heterojunction polymer solar cells (PSCs). The overall power conversion efficiency (PCE) of optimized binary bulk heterojunction PSCs based on P122 :Y6 and P123 :Y6 is 12.60% and 13.16%, respectively. The higher PCE for PSCs based on P123 than P122 counterparts may be associated with the broader absorption profile of the P123 and more charge carrier mobilities than that for the P122 active layer. With the incorporation of small amount of PC₇₁BM into either P122 :Y6 or P123 :Y6 binary blend, the corresponding ternary PSCs showed an overall PCE of 14.89% and 15.52%, respectively, which is higher than the binary counterparts using either Y6 or PC₇₁BM as acceptor. Incorporating the PC₇₁BM in the binary host blend increases the absorption in the 300–500 nm wavelength region, generating more excitons in the active ternary layer and helping to dissociate the excitons into free charge carriers more effectively. The more appropriate nanoscale phase separation in the active ternary layer than the binary counterpart may be one of the reasons for higher PCE.     

Conjugated polymers with broad absorption: Synthesis and application in polymer solar cells

A series of main chain donor‐acceptor low‐bandgap conjugated polymers were designed, synthesized, and used for the fabrication of polymer solar cells. The absorption spectra of low‐bandgap conjugated polymers were tuned by the ratio of three copolymerization monomers. The polymers in films exhibited broad absorption ranging from 300 to 1000 nm with optical bandgaps of around 1.40 eV. All of the polymers have been investigated as an electron donor in photovoltaic cells blending with PCBM ([6, 6]‐phenyl C61‐butyric acid methyl ester) as an electron acceptor and power conversion efficiencies (PCEs) of 1.32–1.8% have been obtained. As for P1 , PCE increases from 1.67 to 2.44% after adding 1,8‐diiodooctance as an additive. The higher PCEs are probably because of better phase separation of blend films. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 2571–2578, 2010     

A novel AH-D-A-type phase junction material to improve photovoltaic performance and device stability in fullerene OSCs

In order to boost power conversion efficiency (PCE) and operation stability of organic solar cells (OSCs), we propose a new idea of phase junction materials (PJMs) used as a photoactive layer component to improve device performance and stability. For this purpose, a novel PJM of H-TRC8 based on rhodanine unit was designed with a conjugated A_H-D-A framework. Here, A_H is a hydrogen-donating electron acceptor unit, D-A is an electron donor-acceptor unit. It is found that H-TRC8 has a good carrier-transporting ability, as well as definite hydrogen-bond and D-A interaction with donor/acceptor materials. While H-TRC8 is added into the PBDB-T/PC₆₀BM blend film with 1.0 vol% DIO (1,8-diiodooctane), the resulting blend film exhibited an enhanced absorption and improved morphology. The intermolecular hydrogen bond between H-TRC8 and PBDB-T plays an important role for them, which is confirmed via FT-IR spectra and 2D ¹H NMR. As a result, the PBDB-T/PC₆₀BM-based devices with 1.25 wt% H-TRC8 and 1.0 vol% DIO exhibit a significantly improved PCE of 8.06%, which is increased by 20.6% in comparison to that in the binary devices with 1.0 vol% DIO only (PCE = 6.68%). Furthermore, the device stability is significantly enhanced with only 43% PCE roll-off at 150 °C for 120 h. This work indicates that A_H-D-A-type PJMs are promising photovoltaic materials used as photoactive-layer components to achieve high-performance fullerene OSCs with high device stability.