We report an enhancement in the efficiency of organic solar cells via the incorporation of gold (Au) or silver (Ag) nanoparticles (NPs) in the hole-transporting buffer layer of poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS), which was formed on an indium tin oxide (ITO) surface by the spin-coating of PEDOT:PSS-Au or Ag NPs composite solution. The composite solution was synthesized by a simple in situ preparation method which involved the reduction of chloroauric acid (HAuCl4) or silver nitrate (AgNO3) with sodium borohydride (NaBH4) solution in the presence of aqueous PEDOT:PSS media. The NPs were well dispersed in the PEDOT:PSS media and showed a characteristic absorption peak due to the surface plasmon resonance effect. Organic solar cells with the structure of ITO/PEDOT:PSS-Au, Ag NPs/poly(3-hexylthiophene):[6,6]-phenyl-C61-butyric acid methyl ester (P3HT:PC61BM)/LiF/Al exhibited an 8% improvement in their power conversion efficiency mainly due to the enlarged surface roughness of the PEDOT:PSS, which lead to an improvement in the charge collection and ultimately improvements in the short-circuit current density and fill factor.
Conjugated polymers, such as poly(3,4-ethylene dioxythiophene) (PEDOT), have emerged as promising materials for interfacing biomedical devices with tissue because of their relatively soft mechanical properties, versatile organic chemistry, and inherent ability to conduct both ions and electrons. However, their limited adhesion to substrates is a concern for in vivo applications. We report an electrografting method to create covalently bonded PEDOT on solid substrates. An amine-functionalized EDOT derivative (2,3-dihydrothieno[3,4-b][1,4]dioxin-2-yl)methanamine (EDOT-NH2), was synthesized and then electrografted onto conducting substrates including platinum, iridium, and indium tin oxide. The electrografting process was performed under slightly basic conditions with an overpotential of ~2 to 3 V. A nonconjugated, cross-linked, and well-adherent P(EDOT-NH2)-based polymer coating was obtained. We found that the P(EDOT-NH2) polymer coating did not block the charge transport through the interface. Subsequent PEDOT electrochemical deposition onto P(EDOT-NH2)-modified electrodes showed comparable electroactivity to pristine PEDOT coating. With P(EDOT-NH2) as an anchoring layer, PEDOT coating showed greatly enhanced adhesion. The modified coating could withstand extensive ultrasonication (1 hour) without significant cracking or delamination, whereas PEDOT typically delaminated after seconds of sonication. Therefore, this is an effective means to selectively modify microelectrodes with highly adherent and highly conductive polymer coatings as direct neural interfaces.
For the realization of high-efficiency flexible optoelectronic devices, transparent electrodes should be fabricated through a low-temperature process and have the crucial feature of low surface roughness. In this paper, we demonstrated a two-step spray-coating method for producing large-scale, smooth and flexible silver nanowire (AgNW)-poly3,4-ethylenedioxythiophene:polystyrenesulfonate (PEDOT:PSS) composite electrodes. Without the high-temperature annealing process, the conductivity of the composite film was improved via the lamination of highly conductive PEDOT:PSS modified by dimethyl sulfoxide (DMSO). Under the room temperature process condition, we fabricated the AgNW-PEDOT:PSS composite film showing an 84.3% mean optical transmittance with a 10.76 Ω sq(-1) sheet resistance. The figure of merit Φ(TC) was higher than that obtained from the indium tin oxide (ITO) films. The sheet resistance of the composite film slightly increased less than 5.3% during 200 cycles of tensile and compression folding, displaying good electromechanical flexibility for use in flexible optoelectronic applications.
A five-layer (5L) graphene on a glass substrate has been demonstrated as a transparent conductive electrode to replace indium tin oxide (ITO) in organic photovoltaic devices. The required low sheet resistance, while maintaining high transparency, and the need of a wettable surface are the main issues. To overcome these, two strategies have been applied: (i) the p-doping of the multilayer graphene, thus reaching 25 Ω □(-1) or (ii) the O2-plasma oxidation of the last layer of the 5L graphene that results in a contact angle of 58° and a sheet resistance of 134 Ω □(-1). A Nd:YVO4 laser patterning has been implemented to realize the desired layout of graphene through an easy and scalable way. Inverted Polymer Solar Cells (PSCs) have been fabricated onto the patterned and modified graphene. The use of PEDOT:PSS has facilitated the deposition of the electron transport layer and a non-chlorinated solvent (ortho-xylene) has been used in the processing of the active layer. It has been found that the two distinct functionalization strategies of graphene have beneficial effects on the overall performance of the devices, leading to an efficiency of 4.2%. Notably, this performance has been achieved with an active area of 10 mm(2), the largest area reported in the literature for graphene-based inverted PSCs.
We describe the conditions for optimal formation of Laser Induced Periodic Surface Structures (LIPSS) over poly(3-hexylthiophene) (P3HT) spin-coated films. Optimal LIPSS on P3HT are observed within a particular range of thicknesses and laser fluences. These conditions can be translated to the photovoltaic blend formed by the 1:1 mixture of P3HT and [6,6]-phenyl C71-butyric acid methyl ester (PC71BM) when deposited on an indium tin oxide (ITO) electrode coated with (poly(3,4 - ethylenedioxythiophene) : poly(styrenesulfonate) (PEDOT:PSS). Solar cells formed by using either a bilayer of P3HT structured by LIPSS covered by PC71BM or a bulk heterojunction with a P3HT:PC71BM blend structured by LIPSS exhibit generation of electrical photocurrent under light illumination. These results suggest that LIPSS could be a compatible technology with organic photovoltaic devices.
Metal mesh is a significant candidate of flexible transparent electrodes to substitute the current state-of-the-art material indium tin oxide (ITO) for future flexible electronics. But there remains a challenge to fabricate metal mesh with order patterns by bottom-up approach. In this work, high-quality Cu mesh transparent electrodes with ordered pore arrays are prepared by using breath-figure polymer films as template. The optimal Cu mesh films present a sheet resistance of 28.7 Ω∙sq-1 at transparency of 83.5%. The work function of Cu mesh electrode is tuned from 4.6 eV to 5.1 eV by Ag deposition and the following short-time UV-ozone treatment, matching well with PEDOT:PSS (5.2 eV) hole extraction layer. The modified Cu mesh electrodes show remarkable potential as the substitute of ITO/PET in the flexible OPV and OLED devices. The OPV cells constructed on our Cu mesh electrodes present similar power conversion efficiency (PCE) of 2.04% as those on ITO/PET electrodes. The flexible OLED prototype devices can achieve a brightness of 10000 cd at operation voltage of 8 V.
A simple O2 plasma processing method for preparation vanadium oxide (V2O5) anode buffer layer on indium tin oxide (ITO) coated glass for polymer solar cells (PSCs) was reported. The V2O5 layer with high transmittance, good electrical and interfacial properties was prepared by spin coating a vanadium(V) triisopropoxide oxide alcohol solution on ITO and then O2 plasma treatment for 10 min (V2O5 (O2 plasma)). PSCs based on P3HT:PC61BM and PBDTTT-C:PC71BM using V2O5 (O2 plasma) as anode buffer layer show high power conversion efficiencies (PCEs) of 4.47% and 7.54% under the illumination of AM 1.5G, 100 mW/cm(2). Compared to the control device with PBDTTT-C:PC71BM as active layer and PEDOT:PSS (PCE of 6.52%) and thermal annealed V2O5 (PCE of 6.27%) as anode buffer layer, the PCE was improved by 15.6% and 20.2% with the introduction of V2O5 (O2 plasma) anode buffer layer. The improved PCE is ascribed to the greatly improved fill factor and enhanced short circuit current density of the devices, which is benefited from the change of work function of V2O5, the surface with lots of dangling bonds for better interfacial contact, and excellent charge transport property of V2O5 (O2 plasma) layer. The results indicate that O2 plasma processed V2O5 film is an efficient and economical anode buffer layer for high-performance PSCs. It also provides an attractive choice for low cost fabrication of organic electronics.
In this article, we have synthesized conductive nanocomposites composed of multi-walled carbon nanotube (MWCNT) and Au nanoparticles (NPs). The Au NPs with an average size of approximately 4.3 nm are uniformed anchored on the MWCNT. After exposing with microwave (MW) plasma irradiation, the anchored Au NPs experience melt and fusion leading larger aggregation (34 nm) which can connect the MWCNT forming a three-dimensional conducting network. The formation of continuous MWCNT network can produce more conductive pathway, leading to lower sheet resistance. With dispersing the Au-MWCNT in the highly conductive polymer, poly(ethylene dioxythiophene): polystyrenesulfonate (PEDOT:PSS), we can obtain solution-processable composite formulations to prepare flexible transparent electrode. The resulting Au-MWCNT/PEDOT:PSS hybrid films possess a sheet resistance of 51 /sq with a transmittance of 86.2% at 550 nm. We also fabricate flexible organic solar cells and electrochromic devices to demonstrate the potential use of the as-prepared composite electrodes. Compared with the indium tin oxide (ITO) based devices, both the solar cells and electrochromic devices incorporated with the composites as transparent electrode deliver a comparable performance.
In this work, we fabricated indium-free perovskite solar cells (SCs) using direct- and dry-transferred aerosol single-walled carbon nanotube (SWNT). We investigated diverse methodologies to solve SWNT’s hydrophobicity and doping issues in SC devices. These include changing wettability of poly(3,4-ethylenedioxythiophene)/poly(styrenesulfonate) (PEDOT:PSS), MoO3 thermal doping, and HNO3(aq) doping with various dilutions from 15 to 70 v/v% to minimize its instability and toxic nature. We discovered that isopropanol (IPA) modified PEDOT:PSS works better than surfactant modified PEDOT:PSS as an electrode in perovskite SCs due to superior wettability, while MoO3 is not compatible owing to energy level mismatching. Diluted HNO3 (35 v/v%)-doped SWCNT-based device performed the highest PCE of 6.32% among SWNT-based perovskite SCs, which is 70% of an indium tin oxide (ITO)-based device (9.05%). Its flexible application showed 5.38% on a polyethylene terephthalate (PET) substrate.
We demonstrate that an easily accessible polyacrylonitrile (PAN) polymer can efficiently function as a novel solution-processable anode interfacial layer (AIL) to boost the device-performances of polymer:fullerene based solar cells (PSCs). The PAN thin film was simply prepared with spin-coating of a cost-efficient PAN solution dissolved in dimethylformamide on indium tin oxide (ITO), and the thin polymeric interlayer on PSC-parameters and -stability were systemically investigated. As a result, the cell-efficiency of the PSC with PAN was remarkably enhanced compared to the device using the bare ITO. Furthermore, with the PAN, we finally achieved an excellent power conversion efficiency (PCE) of 6.7% and a very high PSC stability in PTB7:PC71BM systems, which constitute a highly comparable PCE and superior device life-time to conventional PSCs with poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS). These results demonstrate that the inexpensive solution-processed PAN polymer can be an attractive PEDOT:PSS alternative and is more powerful for achieving better cell-performances and lower cost PSC-production.