Search

Due to the low cost, light weight, semitransparency, good flexibility, and large manufacturing area of organic solar cells (OSCs), OSCs have the opportunity to become the next generation of solar cells in some specific applications. So far, the efficiency of the OSC device has been improved by more than 20%. The optical band gap between the lowest unoccupied molecular orbital (LUMO) level and the highest occupied molecular orbital (HOMO) level is an important factor affecting the performance of the device. Selenophene, a derivative of aromatic pentacyclic thiophene, is easy to polarize, its LUMO energy level is very low, and hence the optical band gap can be reduced. In addition, the selenium atoms in selenophene and other oxygen atoms or sulfur atoms can form an intermolecular interaction, so as to improve the stacking order of the active layer blend film and improve the carrier transport efficiency. This paper introduces the organic solar active layer materials containing selenium benzene in recent years, which can be simply divided into donor materials and acceptor materials. Replacing sulfur atoms with selenium atoms in these materials can effectively reduce the corresponding optical band gap of materials, improve the mutual solubility of donor recipient materials, and ultimately improve the device efficiency. Therefore, the sulfur in thiophene can be completely replaced by selenium or oxygen of the same family, which can be used in the active layer materials of organic solar cells. This article mainly describes the application of selenium instead of sulfur in OSCs. [ABSTRACT FROM AUTHOR]

Organic solar cells (OSCs) have great potential to completely change the development trend of entire industries and become the next generation of commercial solar cells. Compared with polymer solar cells, the nonfullerene all‐small‐molecule organic solar cells (NF‐ASM OSCs) system has the advantages of easy purification, no batch effect, etc. Moreover, their power conversion efficiency (PCE) exceeds the commercialization threshold of 10%. Recently, the diversity of small‐molecule materials and the steady increase in PCE values suggest a bright future for NF‐ASM OSCs. Herein, small‐molecule donor and acceptor materials that have been developed in recent years to produce higher device efficiency are introduced. [ABSTRACT FROM AUTHOR]

Abstract: Recently, research on nonfullerene acceptors in organic solar cells has gradually become a hot topic due to such superior characteristics of light absorption and energy‐level‐convenient manipulation, multiformity of the photoactive material structures, as well as the extensive area in production compared to the fullerene derivatives. However, the nonfullerene acceptors evolved slowly before 2012 and, as a matter of fact, the power conversion efficiency values could only bear 2.0%. Strikingly, nonfullerene acceptors have developed at a fast pace since 2013, with the best device performance of 13.1% now. In this review, recent research progress on nonfullerene acceptors, including small molecules and polymers, are sorted and summarized on the basis of the different characteristics. [ABSTRACT FROM AUTHOR]

Highly efficient nonfullerene polymer solar cells (PSCs) are developed based on two new phthalimide‐based polymers phthalimide‐difluorobenzothiadiazole (PhI‐ffBT) and fluorinated phthalimide‐ffBT (ffPhI‐ffBT). Compared to all high‐performance polymers reported, which are exclusively based on benzo[1,2‐b:4,5‐b′]dithiophene (BDT), both PhI‐ffBT and ffPhI‐ffBT are BDT‐free and feature a D‐A1‐D‐A2 type backbone. Incorporating a second acceptor unit difluorobenzothiadiazole leads to polymers with low‐lying highest occupied molecular orbital levels (≈−5.6 eV) and a complementary absorption with the narrow bandgap nonfullerene acceptor IT‐4F. Moreover, these BDT‐free polymers show substantially higher hole mobilities than BDT‐based polymers, which are beneficial to charge transport and extraction in solar cells. The PSCs containing difluorinated phthalimide‐based polymer ffPhI‐ffBT achieve a substantial PCE of 12.74% and a large Voc of 0.94 V, and the PSCs containing phthalimide‐based polymer PhI‐ffBT show a further increased PCE of 13.31% with a higher Jsc of 19.41 mA cm−2 and a larger fill factor of 0.76. The 13.31% PCE is the highest value except the widely studied BDT‐based polymers and is also the highest among all benzothiadiazole‐based polymers. The results demonstrate that phthalimides are excellent building blocks for enabling donor polymers with the state‐of‐the‐art performance in nonfullerene PSCs and the BDT is not necessary for constructing such donor polymers. Two phthalimide‐based high mobility polymers with a D‐A1‐D‐A2 backbone motif are synthesized. A remarkable power conversion efficiency of 12.74 and 13.31% is achieved from fluorinated phthalimide‐difluorobenzothiadiazole and phthalimide‐difluorobenzothiadiazole‐based nonfullerene polymer solar cells, respectively. The results demonstrate that phthalimides are excellent building blocks for enabling polymer semiconductors with outstanding solar cell performances. [ABSTRACT FROM AUTHOR]

In article number 1801743, Xugang Guo and co‐workers develop two phthalimide‐based polymers featuring a D‐A1‐D‐A2 backbone motif. Eliminating benzodithiophene leads to polymers with substantial mobility. Nonfullerene polymer solar cells utilizing these high‐mobility polymers achieve a remarkable power conversion efficiency >13%. The results demonstrate that phthalimides are excellent building blocks for enabling polymer semiconductors with outstanding solar cell performances and benzodithiophenes are not necessary for constructing such polymers. [ABSTRACT FROM AUTHOR]

• 5-Chlorobenzoxazole was used as solid additive for efficient organic solar cells. • The filling factor was increased from 66.2 % to 71 % by adding additive. • The PCE was improved from 14.8 % to 16.1 %. Adding solid additives to the active layer is a simple and efficient method to adjust the morphology of the active layer to obtain appropriate phase separation, thus improving the organic solar cell device performance. We found a 5-Chlorobenzoxazole molecule as a solid additive to PM6:Y6 system, which increased the filling factor from 66.2 % to 71.0 % and the PCE from 14.8 % to 16.1 %. The results indicate that 5-Chlorobenzoxazole can interact with Y6, thus optimizing the morphology of the active film, enhancing the ability of charge extraction, and further improving FF and PCE. [ABSTRACT FROM AUTHOR]

[Display omitted] • Hole-transporting materials are suitable for use on the anode of 1,1′-bis(3-sulfopropyl) viologen (SPV)-based electrochromic devices. • Driving voltage, optical contrast, response time and coloration efficiency can be tuned by using the hole-transporting materials. • This work paved a new way for boosting electrochromic performances of viologen-based devices via electrode modification of anode by hole-transporting material. In this paper, we present the first application of organic hole-transporting semiconductors 4,4′,4′'-tris(carbazol-9-yl)triphenylamine (TCTA) and 4,4′-cyclohexylbis[N,N-bis(4-methylphenyl) aniline] (TAPC) in electrochromism area, demonstrating that TCTA or TAPC is suitable for use as hole-transporting materials on the anode of 1,1′-bis(3-sulfopropyl) viologen (SPV)-based electrochromic devices. For such devices, we obtain a decreased driving voltage of SPV-based electrochromic devices down to −2.0 V in the presence of TCTA or TAPC with comparison to that of ca. −2.5 V in the absence of the hole-transporting material. The optical contrast of the device increased from 57.19 % (without hole-transport layer) to 66.41 % (TCTA) or 62.97 % (TAPC) at 533 nm. The response time of 66.2 s in the absence of hole-transporting layer can decrease to 30.6 s with TCTA and 62.7 s with TAPC, respectively. The coloration efficiency of the as-fabricated devices at 533 nm can reach from 67.3 cm2/C (SPV-only) up to 153.2 cm2/C (TCTA) and 80.5 cm2/C (TAPC). This work paved a new way for boosting electrochromic performances of viologen-based devices via electrode modification of anode by hole-transporting material TCTA and TAPC which have been used effectively and efficiently in organic electroluminescent devices and solar cells. [ABSTRACT FROM AUTHOR]

• Two non-fullerene acceptors (NFAs) with thiazole π-bridge for organic solar cells were synthesized. • The NFAs demonstrated power conversion efficiencies (PCE) of 6.20% and 6.06%, respectively. • The NFA based F substituted ending group exhibited better organic solar cell performance than the Cl based NFA. Intramolecular noncovalent conformational locks (NoCLs) have been found to be effective in increasing the rigidity and planarity of the molecular backbone. This, in turn, leads to reduced recombination energy and improved intramolecular charge transport mobility, resulting in significant enhancements in the photovoltaic performance of organic solar cell (OSC) devices. To take advantage of this effect, we designed and synthesized two small molecule non-fullerene acceptors (NFAs) with A-π-D-π-A structures using thiazole (Tz): IDTz-IC4F and IDTz-IC4Cl. With the synergistic assistance of NoCLs and halogenated end groups, the NFAs IDTz-IC4F and IDTz-IC4Cl exhibited power conversion efficiencies (PCEs) of 6.20 % and 6.06 %, respectively. This study presents a strategy for enhancing the PCE of OSCs by incorporating cooperative NoCLs and halogen end groups, providing an exciting avenue for designing high-performance non-fullerene materials in the future. [ABSTRACT FROM AUTHOR]

In order to meet the demand of large-scale production of organic solar cells and concept of green chemistry, it is essential to develop environment friendly solvent to fabricate OSCs. In this paper, we utilize thiophene (TH) and diphenyl ether (DPE) as halogen-free processing solvent to optimize performance of OSCs based on PTB7-Th:PC 71 BM, and we choose chlorobenzene (CB) and 1,8-diiodineoctane (DIO) combination as comparison. For PTB7-Th:PC 71 BM blend film based on pure TH solvent, the blend film exhibits high photoelectron conversion, efficient exciton separate and charges collection and well developed morphology properties, thus, higher V oc, J sc and FF were obtained than that of pure CB solvent. Furthermore, excellent photovoltaic performance was achieved with the addition of additive. The PCE of 9.02% from TH:5% DPE system was achieved without any thermal or solvent treatments (the pure TH processed devices PCE is 6.93%), while CB (with 2% DIO) based devices show a lower PCE of 7.41% (the pure CB processed devices PCE is 4.06%). The enhanced photovoltaic performance demonstrates that halogen-free solvent of thiophene provides a new strategy to large-scale fabrication of organic solar cells in future. Image 1 • Halogen free solvent thiophene (TH) was used to make organic solar cells based on PTB7-Th:PC 71 BM. • Compared to halogenated solvent chlorobenzene, cells made from solvent TH achieved higher performance of 6.93%. • TH (with 5% DPE) based devices achieved higher PCE of 9.02%, compared to CB (with 2% DIO) based devices with PCE of 7.41%. [ABSTRACT FROM AUTHOR]

Abstract Two donor-acceptor (D-A) 2-dimensional (2D) conjugated polymers P1 and P2 based on isoindigo (ID) and thienoisoindigo (TID) as acceptor unit and 4,8-bis(5-(2-ethylhexyl)thiophen-2-yl)benzo[1,2-b:4,5-b´]dithiophene (BDT-T) as donor unit were prepared via Stille coupling and characterized by solution-possessed organic field effect transistors (OFETs) and organic solar cells (OSCs), respectively. By changing the electron-withdrawing component of the conjugated polymer backbone from ID to TID, there have also been diversities in the optical absorption, thermal stability, molecular structure, electrochemical energy level, charge mobility and photovoltaic properties of these two polymers. P1 and P2 exhibited intrinsic p-type semiconductor characteristic with hole mobilities of 3.0 × 10−2 and 1.2 × 10−2 cm2 V−1 s−1, respectively. When blended with the [6,6]-phenyl-C 61 -butyric acid methyl ester (PC 61 BM), the highest power conversion efficiency (PCE) of P1 and P2 were 2.40% and 1.28%, respectively. Our results suggest that ID and TID units are useful building blocks for the further development of efficient organic optical-electrical materials. Graphical abstract Image Highlights • 2D conjugated polymers based on isoindigo (ID) and thienoisoindigo (TID) were synthesized. • The ID and TID based polymers showed hole mobilities of 3.0 × 10−2 and 1.2 × 10−2 cm2 V−1 s−1. • The ID based polymer exhibited better organic solar cell performance than the TID based polymer. [ABSTRACT FROM AUTHOR]

Noncovalent conformational locks (NCLs) including S⋯N, Se⋯O, and S⋯O etc. Have been an effective strategy to improve the planarity and rigidity, and charge transport mobility of organic/polymeric semiconductors. Herein, by replacing methyl group (ITMIC) with chlorine (ITCIC) in the π-bridge, the planarity and rigidity of the π-conjugated skeleton was enhanced by introduction of S⋯Cl NCLs, thus the charge transport mobility was improved accordingly. As a result, PM6:ITCIC based organic solar cells showed impressive PCE of 11.34%, much higher than that based on PM6:ITMIC. This contribution demonstrated a novel kind NCLs (S⋯Cl) for improving the performance of organic solar cells. Image 1 [ABSTRACT FROM AUTHOR]