Solution Processable Rhodanine‐Based Small Molecule Organic Photovoltaic Cells with a Power Conversion Efficiency of 6.1%

Abstract

In the past few years, great progress has been made in organic photovoltaic (OPV) cells for an alternate of silicon semiconductorbased solar cells. OPV has the advantages of clean, low-cost, flexibility, and the possibility of roll-to-roll production. [1][2][3][4] Currently, most of the works have been focused on polymer donor molecules using bulk heterojunction (BHJ) architecture and [6,6]-phenyl-C61-butyric acid methyl ester (PC 61 BM) as the acceptor. [5,6] Indeed, in addition to the currently better OPV performance than small molecules, polymers have the advantages for such as better film forming quality and so on. [7] However, it cannot be denied that there are disadvantages for polymer-based OPV, such as batch to batch reproducibility, difficulty of purification, and so on. In contrast, small molecules intrinsically do not have such flaws; [8] additionally, their band structures could be tuned easily with much more choices of chemical modification. Furthermore, small molecules generally have higher charge mobility and open voltages. [9,10] However, even with these advantages, small-molecule-based OPV cells have not been investigated as intensively as that of their polymer counterparts because one of the major problems for small molecules is their generally poor film quality when using the simple solution spinning process. [11] This has been hampering their performance, and indeed their power conversion efficiencies (PCEs) (4%-5%) [12][13][14][15][16][17][18] are still significantly lower compared with that (>7%) [19][20][21][22][23][24][25] from polymers. It is thus expected that better PCE could be achieved when their intrinsic bad film quality and morphology in BHJ architecture could be improved combining with their other advantages. But to achieve this, careful molecule design has to be carried out to address many factors collectively, including their molar absorption, morphology compatibility with the acceptors for a better film quality, and so on.Previously, we have reported a small molecule (DCAO7T, Scheme 1), which gives rather high quality of solution spincoated film and a high 5.08% PCE. [12] But this molecule comes with an end unit of cyanoacetate group, which could not contribute too much for the overall solar absorption. So, we thought that the current density J sc might be able to be enhanced if structures with stronger molar absorption is used to replace such an end unit, in the conditions that overall molecular backbone and morphology will not be affected too much. Considering the generally high absorption coefficients and good OPV performance of many dye molecules, such as triarylamines, [16,26] acenaphthoquinoxaline, [27] diketopyrrolopyrroles (DPP), [17] squaraines, [18,28,29] merocyanine, [30,31] isoindigo, [32] pthalocyanine, [33] and dipyrromethene boron difluoride (BODIPY), [34][35][36] we thus introduce a new dye unit, 3-ethylrhodanine, into the targeted OPV molecule named as DERHD7T (Scheme 1) with a conjugated thiophene backbone. With such a design, DERHD7T is expected to have a str...

Understanding Charge Transport in Molecular Blend Films in Terms of Structural Order and Connectivity of Conductive Pathways

“…This notion is consistent with the fact that virtually all soluble molecular donor materials blended with PC 71 BM to date have optimal solar cell performance at donor concentrations less than 80%. [ 1,2,[23][24][25][26] The trends in hole mobility as a function of donor concentration, shown in Figure 1 C, are notably different than that of the electron mobilities. In the case of T1:PC 71 BM, the hole mobility is remarkably similar across the entire measurable range of donor concentrations with a value of approximately 8 × 10 −4 cm 2 V −1 s −1 .…”

CuSCN as selective contact in solution-processed small-molecule organic solar cells leads to over 7% efficient porphyrin-based device

“…The presence of 3-ethyl-rhodanine in these molecules effectively decreases the band gaps and extends their absorption into the NIR region. 22 The fluorescence spectra of both porphyrins showed similar emission bands at 748 nm and 750 nm respectively. The transition energy i.e.…”

Third- and high-order nonlinear optical properties of an intramolecular charge-transfer compound

“…Organic p-conjugated molecules have been extensively studied and applied in diverse elds ranging from eld-effect transistors (FETs), 1,2 organic light-emitting diodes (OLEDs), 3,4 and organic photovoltaic cells (OPVs), [5][6][7] thanks to their attractive optoelectronic properties. p-Conjugated compounds with electron donors (D) and electron acceptors (A) typically feature a intramolecular charge transfer (ICT) process.…”