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2014年兩維共軛光伏聚合物的側(cè)鏈設(shè)計(jì)規(guī)律 已有1人參與
聚合物光伏材料的分子結(jié)構(gòu)與其光伏性能具有十分密切的關(guān)系。2011年中科院化學(xué)所的研究人員首次將兩維共軛結(jié)構(gòu)引入到苯并二噻吩(BDT)單元中,設(shè)計(jì)了噻吩取代BDT兩維共軛結(jié)構(gòu)單元,并將這一單元與各種共軛結(jié)構(gòu)單元共聚,獲得了一系列的具有兩維共軛結(jié)構(gòu)的共軛聚合物。這類兩維共軛聚合物與烷氧基取代的對(duì)應(yīng)聚合物相比,光伏能量轉(zhuǎn)換效率(PCE)都得到了有效的提升。其中基于二維共軛聚合物PBDTTT-C-T的常規(guī)器件的效率達(dá)到7.6%(Angew. Chem. Int. Ed., 2011, 50, 9697)。2012年,他們與香港大學(xué)/華南理工大學(xué)合作,通過使用新型器件結(jié)構(gòu),使PBDTTT-C-T的光伏效率進(jìn)一步提高到9% ( Adv. Mater. 2012,24,3046; Adv. Mater. 2014, 26, 4043)。
最近他們?cè)趦删S共軛苯并二噻吩(2D-BDT)單元的進(jìn)一步開發(fā)和優(yōu)化方面取得了一系列進(jìn)展。他們將線性烷硫基引入到PBDTTT-EFT上,設(shè)計(jì)合成了PBDT-TS1, 基于PBDT-TS1/PC71BM的單結(jié)正向器件效率高達(dá)9.5%,是目前世界上最高的結(jié)果( Chem. Mater. 2014, 26, 3603)。 同時(shí),他們將三種共軛側(cè)鏈:噻吩烷基、呋喃烷基、硒吩烷基引入到PBDTTT-EFT上,設(shè)計(jì)的新型聚合物PBDTTT-EFS也達(dá)到8.8%(Macromolecules, 2014,DOI: 10.1021/ma500829r)。以PBDTTT-C-T、PBDT-TS1為突出代表的兩維共軛聚合物被國(guó)內(nèi)外同行認(rèn)為是目前最為優(yōu)異的一類聚合物光伏材料,2014年他們應(yīng)邀在Accounts of Chemical Reserch 上撰寫綜述,總結(jié)了兩維共軛聚合物的側(cè)鏈設(shè)計(jì)規(guī)律( Acc. Chem. Res. 2014, 47, 1595)。
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Recently, the benzodithiophene- (BDT-) based polymers with conjugated side groups attracted considerable attention due to their superior properties in polymer solar cells (PSCs), so the investigation of the side chain effects on the photovoltaic properties of this type of polymers is an interesting and important topic for molecular design. Herein, three conjugated polymers based on BDT and thieno[3,4-b]thiophene units with furan, thiophene and selenophene as side groups, named as PBDTTT-EFF, PBDTTT-EFT, and PBDTTT-EFS, were synthesized and applied in polymer solar cells. The polymers were characterized in parallel by absorption spectroscopy, thermogravimetric analysis (TGA), density functional theory (DFT), ultraviolet photoemission spectroscopy (UPS), X-ray diffraction (XRD), and photovoltaic measurements. The results show that the dihedral angles between the BDT and conjugated side groups play important roles in affecting the absorption bands, HOMO levels, crystallinities, and aggregation sizes of the polymers. The photovoltaic results indicate that PBDTTT-EFT and PBDTTT-EFS show similar photovoltaic characteristics in device, and PCEs of 9.0% and 8.78% were obtained, respectively. The device of PBDTTT-EFF shows a Voc of 0.69 V and a Jsc of 11.77 mA/cm2, which are lower than those in the devices based on the other two polymers. Overall, this work suggests that the photovoltaic properties of the BDT-based polymers can be effectively tuned by introducing conjugated side groups with varied steric hindrance.![2014年兩維共軛光伏聚合物的側(cè)鏈設(shè)計(jì)規(guī)律]()
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