Results 1 - 10 of 647
Results 1 - 10 of 647. Search took: 0.018 seconds
|Sort by: date | relevance|
[en] Highlights: • Si nanocrystals (NCs) are added into the classical P3HT:PCBM organic solar cells. • The power conversion efficiency may increase by ~40% when Si NCs are added. • Si NCs improved solar cell absorption, structure and energy-level alignment. Inorganic/organic ternary hybrid structures are emerging as promising candidates for the fabrication of novel solar cells. As one of the most important inorganic solar cell material, silicon (Si) is worth careful exploration during the preparation of the hybrid structures. Here we incorporate the nanoscale form of Si, Si nanocrystals (NCs), into the classical bulk-heterojunction organic solar cells based on poly (3-hexylthiophene) (P3HT) and [6,6]-phenyl-C61-butyric acid methyl ester (PCBM). It is found that the solar cell efficiency may increase by ~ 40% when ~ 5% of PCBM in the original P3HT:PCBM blend is replaced with Si NCs. The efficiency enhancement is enabled by the improved short-wavelength absorption, optimized film structure and cascade energy-level alignment.
[en] The effect of PQT-12 interface layer on the performance of PCDTBT:PCBM based bulk heterojunction (BHJ) organic solar cells (OSCs) is reported in this paper. The PQT-12 interface layer is obtained by cost and material effective technique, floating film transfer method (FTM). It is shown that the use of FTM-based PQT-12 HTL significant improves the power conversion efficiency (PCE) and external quantum efficiency (EQE) of the OSCs over only PEDOT:PSS HTL based OSCs. The OSC has the maximum values of JSC (=5.62 mA cm−2), VOC (=562 mV) and FF (=0.33) in the PQT-12 incorporated structure due to efficient carrier transfer at the interface. The PCE of nearly twice of the only PEDOT:PSS HTL OSC is obtained in case of the PQT-12/PEDOT:PSS structure. (paper)
[en] Post-production annealing which improves the power conversion efficiency of the P3HT:PCBM-based organic cells are very important process. Lots of various annealing temperatures and annealing times have been used for annealing process in previous studies but not any criteria was taken as a basis for determination of annealing temperature. In this study annealing temperature was optimized for annealing time of 3 min ITO-PEDOT:PSS/P3HT:PCBM/Al was fabricated at the weight ratio of 12:8 for P3HT:PCBM. Organic solar cells were annealed at different annealing temperatures in the range of 80 °C–160 °C. The variation of external quantum efficiency (EQE) with annealing temperature was obtained. The higher EQE was obtained at 120 °C. Thus, 120 °C was determined as optimum annealing temperature. The aging experiments were performed under constant humidity, illumination and atmospheric conditions. It has been observed that the post- product annealed at 120 °C solar cells have more longer life time and more stable compared with the non-annealed cell and other annealed solar cells. (paper)
[en] Controlling the morphology of bulk-heterojunction (BHJ) films in organic photovoltaics (OPVs) is critical in overcoming inherent drawbacks (short exciton diffusion length and low charge mobility) of organic materials and achieving optimal device efficiency. Taking into account the energy conversion process, it is important to understand the hierarchical structure in organic solar cells ranging from molecule-scale and domain-scale to device-scale structure to realize efficient charge separation, transfer, and extraction. However, most of research has so far focused on the domain-level structure such as crystallinity, domain size, and domain orientation because there lacks methods to control hierarchical structures and systematic studies on it. In the present study, we report a new approach to control hierarchical structures in organic solar cells, which was characterized by PSoXS and SANS and their relationship with device performance. We could induce highly anisotropic P3HT crystalline structures (P3HT nanowires), which were grown in a direction of pi-pi stack, facilitating charge transport, through adding poor solvents for P3HT. In addition, the anisotropy of P3HT nanowire was controlled by utilizing additives which have different affinity with PCBM. By employing controlled P3HT nanowires having different anisotropy and following thermal annealing process, we could control the molecular orientation of P3HT at PCBM interfaces (molecular-scale), domain sizes of P3HT and PCBM (domain-scale) and network structures (device-scale). Based on our new method, we could effectively control the hierarchical structures of organic solar cells with an overall view on the relationship between multiscale nanostructure and device performance.
[en] We demonstrate a new interpretation of the previously reported quadrimolecular recombination in organic bulk heterojunction solar cells. It is suggested that the recently described (Szmytkowski 2012 Phys. Status Solidi RRL 6 300) interaction between exciton and electron–hole Langevin bound pair formed across the donor–acceptor interface is a four-particle process. This is in opposition to the treatment of this effect as a three-particle phenomenon which might be intuitively expected because one exciton annihilates physically on one charge carrier. An excellent agreement between experimental data and theoretical calculations has been obtained. The novelty of the presented interpretation is of fundamental importance to understand mechanisms which limit the efficiency of organic solar cells. (fast track communication)
[en] Furan and thiophene-substituted acceptor–donor–acceptor type soluble small molecules (SM1 and SM2) with absorption extending to 800 nm were synthesized and evaluated in solar cells combining with [6,6]-phenyl-C-61-butyric acid methyl ester (PC61BM). The organic solar cells (OSCs) were optimized with different processing conditions, such as thermal annealing. The performances of the OSCs were more than double enhanced by thermal annealing. The highest power conversion efficiency of 5.5% was achieved in OSCs based on SM2:PC61BM in a weight ratio of 1:1 annealed at 120 °C. In addition, the correlations between molecular structures and opto-electric properties as well as the performance of OSCs were also investigated, which indicates that replacing oxygen O with sulfur S on a main chain has much stronger influence on molecular property. These results will be very useful for further designing new molecules with even better property for OSCs.
[en] Highlights: • Isoindigo (II) was directly coupled to carbazole (C) to give C-II-C. • II was coupled to the 9-phenyl group of C to give P-II-P. • The band gaps of C-II-C and P-II-P were 1.85 and 1.90 eV, respectively. • C-II-C is more planar and more conjugated than P-II-P. • C-II-C-based solar cells showed the best power conversion efficiency of 0.44%. 6,6′-Dibromo-N,N′-(2-octyldodecanyl)isoindigo was coupled to either 4-(N-carbazolyl)phenyl boronic acid or 9-phenyl-9H-carbazole-3-boronic acid to give two different conjugated molecules of P-II-P and C-II-C, respectively. The optical band gap/HOMO levels of P-II-P and C-II-C were 1.90/−5.60 eV and 1.85/−5.39 eV, respectively. Based on the experimental and calculation data, C-II-C is more highly conjugated than P-II-P. The performances of C-II-C-based photovoltaic devices were better than those of P-II-P-based devices, with the best power conversion efficiency of 0.44%.
[en] An anomalous behavior—a change in polarity with the passage of time in the bulk heterojunction poly(3-hexylthiophene) (P3HT):6,6-phenylC61 butyric acid methyl ester (PCBM) organic solar cells—is reported here. This work is a continuation of our previous work where the initial degradation of the organic solar cells, freshly prepared up to 4 h, was mainly due to domain formation in the active layer. With the passage of time, the activity at the interfaces starts becoming significant. A decrease of VOC and JSC, leading to a change in polarity, has been reported and explained up to 300 h after fabrication.
[en] Ionic silsesquioxane-capped gold nanoparticle powders presenting narrow size distribution were synthesised, characterised and applied in the assembly of organic solar cells. The assembled devices were electrically modelled, and the nanoparticles encapsulated with a charged pendant silsesquioxane were found to provide enhanced photocurrent, and to result in better electrical properties than those capped with bridged double-charged silsesquioxane. Therefore, thinner layers of encapsulation result in higher efficiency.
[en] Highlights: • Electrochemistry on thiadiazine-based compounds. • Energy level approximation. • Low-bandgap copolymer electron accepting building blocks. • Design rules for “push–pull” copolymerization approaches using thiadiazines. -- Abstract: A series of synthesized small organic molecules based on the 4H-1,2,6-thiadiazine moiety are studied using electrochemistry, to probe their potential as comonomer building blocks for solar-absorbing polymers for organic solar cells. This is the first instance of an electrochemical report for this family of heterocycles. Structure–physical property relationships are identified that can guide future synthetic efforts. Parameters that can influence the properties of the final copolymer such as the choice of electron donor comonomer and the energy level of the fullerene adduct acceptor are factored-in and discussed and the thiadiazines that can meet the requirements are singled-out