Burkhart Beate, Khlyabich Petr P, Thompson Barry C
Department of Chemistry, Loker Hydrocarbon Research Institute, and Center for Energy Nanoscience, University of Southern California, Los Angeles, California 90089-1661, United States.
ACS Macro Lett. 2012 Jun 19;1(6):660-666. doi: 10.1021/mz300197c. Epub 2012 May 11.
Five novel semi-random poly(3-hexylthiophene) (P3HT) based donor-acceptor copolymers containing either thienopyrroledione (TPD) or both diketopyrrolopyrrole (DPP) and TPD acceptors were synthesized by Stille copolymerization, and their optical, electrochemical, charge transport, and photovoltaic properties were investigated. Poly(3-hexylthiophene-thiophene-thienopyrroledione) polymers P3HTT-TPD-10% and P3HTT-TPD-15% with either 10% or 15% acceptor content were synthesized as a point of reference. Two-acceptor polymers containing both TPD and DPP were synthesized with varying acceptor ratios to fine-tune electrooptical properties, namely, P3HTT-TPD-DPP (1:1) (7.5% TPD and 7.5% DPP), P3HTT-TPD-DPP (2:1) (10% TPD and 5% DPP), and P3HTT-TPD-DPP (1:2) (5% TPD and 10% DPP). The two-acceptor copolymers have broad and uniformly strong absorption profiles from 350-850 nm with absorption coefficients up to 8 × 10 cm at ∼700 nm for P3HTT-TPD-DPP (1:2). This is reflected in the photocurrent responses of polymer:fullerene bulk heterojunction solar cells with PCBM as an acceptor where P3HTT-TPD-DPP (1:1) and P3HTT-TPD-DPP (1:2) have peak external quantum efficiency (EQE) values of 61% and 68% at 680 nm, respectively, and at 800 nm show impressive EQE values of 29% and 40%. Power conversion efficiencies in solar cells of P3HTT-TPD-10% and P3HTT-TPD-15% are moderate (2.08% and 2.22%, respectively), whereas two-acceptor copolymers achieve high efficiencies between 3.94% and 4.93%. The higher efficiencies are due to a combination of very large short-circuit current densities exceeding 16 mA/cm for P3HTT-TPD-DPP (1:2), which are among the highest published values for polymer solar cells and are considerably higher than those of previously published two-acceptor polymers, as well as fill factors over 0.60. These results indicate that semi-random copolymers containing multiple distinct acceptor monomers are a very promising class of polymers able to achieve large current densities and high efficiencies due to favorable properties such as semicrystallinity, high hole mobility, and importantly broad, uniform, and strong absorption of the solar spectrum.
通过Stille共聚反应合成了五种新型的基于聚（3-己基噻吩）（P3HT）的供体-受体共聚物，这些共聚物含有噻吩并吡咯二酮（TPD）或同时含有二酮吡咯并吡咯（DPP）和TPD受体，并对其光学、电化学、电荷传输和光伏性能进行了研究。合成了受体含量为10%或15%的聚（3-己基噻吩-噻吩-噻吩并吡咯二酮）聚合物P3HTT-TPD-10%和P3HTT-TPD-15%作为参考。合成了同时含有TPD和DPP的双受体聚合物，通过改变受体比例来微调电光性能，即P3HTT-TPD-DPP（1:1）（7.5% TPD和7.5% DPP）、P3HTT-TPD-DPP（2:1）（10% TPD和5% DPP）以及P3HTT-TPD-DPP（1:2）（5% TPD和10% DPP）。双受体共聚物在350 - 850 nm范围内具有宽泛且均匀的强吸收光谱，对于P3HTT-TPD-DPP（1:2），在约700 nm处的吸收系数高达8×10 cm 。这反映在以PCBM为受体的聚合物：富勒烯本体异质结太阳能电池的光电流响应中，其中P3HTT-TPD-DPP（1:1）和P3HTT-TPD-DPP（1:2）在680 nm处的峰值外量子效率（EQE）值分别为61%和68%，在800 nm处显示出令人印象深刻的EQE值分别为29%和40%。P3HTT-TPD-10%和P3HTT-TPD-15%太阳能电池的功率转换效率适中（分别为2.08%和2.22%），而双受体共聚物的效率在3.94%至4.93%之间。较高的效率归因于多种因素的组合，对于P3HTT-TPD-DPP（1:2），其短路电流密度非常大，超过16 mA/cm ，这是聚合物太阳能电池已发表的最高值之一，并且远高于先前发表的双受体聚合物，以及填充因子超过0.60。这些结果表明，含有多种不同受体单体的半无规共聚物是一类非常有前途的聚合物，由于其具有诸如半结晶性、高空穴迁移率以及对太阳光谱的宽、均匀且强吸收等有利特性，能够实现大电流密度和高效率。
