Alcohol-soluble Star-shaped Oligofluorenes as Interlayer for High Performance Polymer Solar Cells

Abstract

Two star-shaped oligofluorenes with hexakis(fluoren-2-yl)benzene as core are designed and sythesized for interfacial materials in polymer solar cell. Diethanolamino groups are attached to the side chain of fluorene units for T0-OH and T1-OH to enable the alcohol solubility, and additional hydrophobic n-hexyl chains are also grafted on the increased fluorene arms for T1-OH. In conventional device with PCDTBT/PC71BM as active layer, a 50% enhanced PCE is obtained by incorporating T0-OH and T1-OH as the interlayer compared with device without interlayer. By optimizing the active material with PTB7 and with the inverted device structure, a maximum PCE of 9.30% is achieved, which is among the highest efficiencies for PTB7 based polymer solar cells. The work function of modified electrode, the surface morphology and the suraface properties are systematically studied. By modifying the structures of the star-shaped molecules, a balance between the hydrophobic and hydrophilic property is finely tuned, and thus facilitate the interlayer for high performance of PSCs.

Regular Organic Solar Cells with Efficiency over 10% and Promoted Stability by Ligand‐ and Thermal Annealing‐Free Al‐Doped ZnO Cathode Interlayer

“…The PTB7:PC 71 BM solar cell delivered an excellent performance with a high efficiency of 9.13% ( Figure 6 a), which is comparable to the devices based on other interlayers,42, 43, 50 presenting huge enhancement compared to the PCE 7.59% reported by Ackermann 23. For the PffBT4T‐2OD:PC 71 BM blend, deposition was optimized by controlling the dropping and spin‐coating process to obtain a homogeneous morphology and optimal thickness due to the strong crystallization and temperature‐dependent aggregation behavior 10, 51.…”

Small Molecule Interlayers in Organic Solar Cells

“…As a result, the device efficiency was prominently increased from 4.06% (without interlayer) to 7.21% in poly[N‐9‐hepta‐decanyl‐2,7‐carbazole‐alt‐5,5‐(4′,7′‐di‐2‐thienyl‐2′,1′,3′‐benzothiadiazole)] (PCDTBT):PC 71 BM devices. In addition to the TPA core, Yang and co‐workers developed a series of star‐like SM‐CIMs based on hexakis(fluoren‐2‐yl)benzene (HFB) (T1‐OH and Tn1) or triazine core (Tf1 and Tf2) . For example, T1‐OH (Scheme ) was synthesized, based on a HFB core and fluorine arms with diethanolamino groups .…”

“…In addition to the TPA core, Yang and co‐workers developed a series of star‐like SM‐CIMs based on hexakis(fluoren‐2‐yl)benzene (HFB) (T1‐OH and Tn1) or triazine core (Tf1 and Tf2) . For example, T1‐OH (Scheme ) was synthesized, based on a HFB core and fluorine arms with diethanolamino groups . On the one hand, the diethanolamino groups reduced the WF of the cathode electrode, facilitating electron collection.…”

Synthesis of alcohol soluble hexakis(fluoren-2-yl)benzene based on phosphate groups and their application in inverted polymer solar cells

“…六芴基苯是一类具 有星型 π 共轭结构的寡聚物, 6 个芴单元通过 2 位连 接于中心苯环, 同时芴的 9 位引入长烷基链, 使得这 类分子具有良好的溶解性、成膜性能以及高热稳定性. 最近, 我们在芴的侧链末端引入氮羟乙基, 将其作为 修饰 ITO 电极的界面材料, 取得了良好的器件性 能 [26] . [27] .…”