Inverted-type Solar Cells Research Articles

High stability of benzotriazole and benzodithiophene containing medium band-gap polymer solar cell

The improvement of polymer solar cell stability is a challenge for the scientists and has significant implications commercially. In this study, we investigated the stability of a novel P-SBTBDT active material applied in an inverted type solar cell. Detailed stability experiments comprising shelf life, laboratory weathering and outdoor testing were carried out according to ISOS testing guidelines. Shelf life showed that P-SBTBDT solar cells were very stable after 840h with encapsulation. Although accelerated weathering aging tests are a very harsh, the devices remained stable after the burn-in phase with T50 from 700 to 840h, with some P-SBTBDT solar cells did not reach T50 in the time span of the test. Degradation tests on the P-SBTBDT solar cells which were carried out under natural solar light indicated that T40 was reached after 840h. The results of dark, light, damp and dry stability tests showed that most of the degradation was provoked by failure of the encapsulation. The experiments indicated that P-SBTBDT solar cells are sensitive to light and oxygen but are strikingly stable under humid conditions. Further developments for minimizing the degradation effects using UV-filters and better encapsulation are some of the necessary improvements in further research.

Improvement of photovoltaic performance and stability of AnE-PV:PCBM based organic solar cells using solution processed inverted geometry

Organic bulk heterojunction and inverted type solar cells were fabricated using AnE-PVstat:PCBM blends as photoactive layers. The device was inverted using thin films of TiO2 as hole blocking and electron conducting layers. The power conversion efficiency (PCE) of organic bulk heterojunction solar cells increased from 1.70% to 2.59% when inverted device configuration was used instead of regular organic bulk heterojunction solar cell configuration. Stability studies reveal that the inverted type devices are more stable than the herein investigated regular organic bulk heterojunction solar cells fabricated using AnE-PVstat:PCBM blends as photoactive layers.

Fabrication of efficient organic and hybrid solar cells by fine channel mist spray coating

Three types of organic and hybrid photovoltaics, which include poly(3-hexylthiophene) (P3HT), [6, 6]-phenyl C61 butyric acid methyl ester (PCBM) and zinc oxide (ZnO) in their active layer as normal, inverted and hybrid solar cells, were prepared by fine-channel mist-spray coating in air. In particular, we investigated the donor/acceptor blending effect for increasing reproducibility in normal type, annealing temperature control for more effective ZnO layer in inverted type solar cells. Patterns of sparse and vertical distribution by solvent polarity were discussed in fabrication for hybrid solar cells. Consequently, enough blending of donor/acceptor solution, the combination of pre/post-heat treatment for ZnO layer and trade-off relation between crystallization of ZnO and ordering of the P3HT matrix were factors to be considered for enhanced results in terms of high photovoltaic performance.

All-polymer solar cells with in-situ generated n-type conjugated polymer nanoparticles

We report all-polymer solar cells with new electron-accepting (n-type) polymer nanoparticles, poly(2,7-bis(4-hexylthiophen-2-yl)-9H-fluoren-9-one-co-benzothiadiazole) (BHTF-co-BT), which were in-situ generated during polymerization reaction. The size of the BHTF-co-BT nanoparticles was ca. 5–15nm with a particular single X-ray diffraction peak (d-spacing=1.3nm), indicative of a highly ordered crystalline state, while their glass transition temperature was ~140°C. Their band gap energy and ionization potential were 1.8eV and 5.7eV, respectively. The possibility of the BHTF-co-BT nanoparticles as an electron acceptor for both normal-type and inverted-type all-polymer (polymer:polymer) solar cells was examined by employing poly(3-hexylthiophene) (P3HT) as an electron donor. The normal-type P3HT:BHTF-co-BT solar cells exhibited promising open circuit voltage (Voc=0.67–0.73V) and fill factor (FF=51.3%), while a three-fold improved short circuit current density and higher Voc (0.77V) were achieved for their inverted-type solar cells.

Effect of nanostructured ZnO cathode layer on the photovoltaic performance of inverted bulk heterojunction solar cells

Inverted bulk heterojunction solar cells have recently captured high interest due to their stability and lifetime. The inverted-type configuration protects cells from the damage by oxygen and moisture in air. This has been achieved by the development of solution processable n-type semiconductors. TiO2 and ZnO are mainly used as cathode electrode layers and air stable Au electrode replaces with air sensitive Al electrode in inverted-type solar cells. In this paper, inverted bulk heterojunction solar cells are fabricated based on poly(3-hexylthiophene) (P3HT) and the N,N′-bis-dehydroabietyl-3,4,9,10-perylene dimide (PDI) materials. Solution processable ZnO cathode layer is used as electron collecting electrode. Bulk heterojunction solar cells are characterized using different blend ratios (1:1, 1:2 and 1:3) of P3HT and PDI. Nanostructured morphologies of P3HT:PDI composite films are investigated by means of Atomic Force Microscopy, which are correlated with device performance. Better device performance is observed in a flat ZnO cathode electrode layer/P3HT:PDI/Gold device configuration with the 1:3 blend ratio of P3HT:PDI film. A poly(3-hexylthiophene) (P3HT)-based inverted bulk heterojunction solar cell using PDI as acceptor is achieved an open-circuit voltage of 350 mV, current density of 0.72 mA/cm2 leading to a power conversion efficiency (IPCE) of 8.2%.

Highly durable inverted-type organic solar cell using amorphous titanium oxide as electron collection electrode inserted between ITO and organic layer

An indium tin oxide/titanium oxide/[6,6]-phenyl C 61 butyric acid methyl ester:regioregular poly(3-hexylthiophene)/poly(3,4-ethylenedioxylenethiophene):poly(4-styrene sulfonic acid)/Au type organic solar cell (ITO/TiO x /PCBM:P3HT/PEDOT:PSS/Au) with 1 cm 2 active area, which is called “inverted-type solar cell”, was developed using an ITO/amorphous titanium oxide (TiO x ) electrode prepared by a sol–gel technique instead of a low functional electrode such as Al. The power conversion efficiency ( η) of 2.47% was obtained by irradiating AM 1.5G-100 mW cm −2 simulated sunlight. We found that a photoconduction of TiO x by irradiating UV light containing slightly in the simulated sunlight was required to drive this solar cell. The device durability in an ambient atmosphere was maintained for more than 20 h under continuous light irradiation. Further, when the air-stable device was covered by a glass plate with a water getter sheet which was coated by an epoxy-UV resin as sealing material, the durability was still higher and over 96% of relative efficiency was observed even after continuous light irradiation for 120 h.