Here we report the fabrication and lifetime analysis of PSCs applying a thin film of Pb[ZrxTi1-x]O3 (PZT) ferroelectric oxide as the ETM. The PZT was made as dense thin film and applied in planar configuration PSCs of the type: FTO/PZT/CsMAFA/ spiro-OMeTAD/Au, where CsMAFA refers to the halide perovskite material with formula Cs5(MA0.17FA0.83)(95)Pb(I0.83Br0.17)3 and PZT refers to the nominal composition Pb[Zr0.6Ti0.4]O3. For comparison purposes, reference solar cells were made applying SnO2 as dense ETM as in FTO/SnO2/CsMAFA/spiro-OMeTAD/
Au. We also explored the effect of the PZT layer on the triple cation perovskite under illumination with respect to solar cell stability. Analysis of the solar cells were made at 1-sun AM 1.5 G, including UV light, in air (no encapsulation), at 45 ºC and 55% RH. The solar cells were poled up to 2 V in order to polarize the PZT electrode. Poling resulted in a slow but steady improvement of the photovoltaic properties of the PZT-based PSC. The improvement was observed during the first 90 minutes after which the device stabilized and then maintained its photovoltaic properties under continuous illumination in air for hours. Our results demonstrate, for the first time, the possibility of applying the PZT ferroelectric oxide as ETM in air and UV-stable PSCs.
In this study, we investigated inverted hybrid bulk-heterojunction solar cells with the following configuration: fluorine-doped tin oxide (FTO) |TiO2/RGO|P3HT:PC61BM|V2O5 or PEDOT:PSS|Ag. The TiO2/GO dispersions were prepared by sol-gel method, employing titanium isopropoxide and graphene oxide (GO) as starting materials. The GO concentration was varied from 0.1 to 4.0 wt%. The corresponding dispersions were spin-coated onto FTO substrates and a thermal treatment was performed to remove organic materials and to reduce GO to reduced graphene oxide (RGO). The TiO2/RGO films were characterized by x-ray diffraction, Raman spectroscopy, and microscopy techniques. Atomic force microscopy (AFM) images showed that the addition of RGO significantly changes the morphology of the TiO2 films, with loss of uniformity and increase in surface roughness. Independent of the use of V2O5 or PEDOT: PSS films as the hole transport layer, the incorporation of 2.0 wt% of RGO into TiO2 films was the optimal concentration for the best organic photovoltaic performance. The solar cells based on TiO2/RGO (2.0 wt%) electrode exhibited a ∼22.3% and ∼28.9% short circuit current density (Jsc) and a power conversion efficiency enhancement, respectively, if compared with the devices based on pure TiO2 films. Kelvin probe force microscopy images suggest that the incorporation of RGO into TiO2 films can promote the appearance of regions with different charge dissipation capacities.
In this work we present the synthesis and photovoltaic application of four different vertically-aligned ZnO
nanostructured electrodes: ZnO nanorods prepared by the a) low-temperature hydrothermal method (LT-HM) and the b) autoclave method (A-HM), c) ZnO nanotrees (NTs) and d) ZnO core-shell NRs with an indium sulfide layer as the shell
(CS). The electrodes have been applied in Dye sensitized solar cells (DSCs) and Polymer solar cells (PSCs). The
photovoltaic properties of each type of nanostructured electrode were optimized separately. Our results show that the
optimal power conversion efficiency depends in great extent on NR dimensions (length and diameter) and the final ZnO nanostructure. In this respect, we have observed an increase in power conversion efficiency when the NR nanostructure is modified as follows: ZnO NRs LT-HM < A-HM < NT< CS for Dye semnsitized solar cells. In the case of PSCs the best power conversion efficiency was obtained for the CS sample.
This work is part of the inter-laboratory collaboration to study the stability of seven distinct sets of state-of-the-art organic photovoltaic (OPVs) devices prepared by leading research laboratories. All devices have been shipped to and degraded at the Danish Technical University (DTU, formerly RISO-DTU) up to 1830 hours in accordance with established ISOS-3 protocols under defined illumination conditions. In this work we present a summary of the degradation response observed for the NREL sample, an inverted OPV of the type ITO/ZnO/P3HT:PCBM/PEDOT:PSS/Ag/Al, under full sun stability test. The results reported from the combination of the different characterization techniques results in a proposed degradation mechanism. The final conclusion is that the failure of the photovoltaic response of the device is mainly due to the degradation of the electrodes and not to the active materials of the solar cell.
Seven distinct sets (n ≥ 12) of state of the art organic photovoltaic devices were prepared by leading research laboratories in a collaboration
planned at the Third International Summit on Organic Photovoltaic Stability (ISOS-3). All devices were shipped to DTU and characterized
simultaneously up to 1830 h in accordance with established ISOS-3 protocols under three distinct illumination conditions: accelerated full sun
simulation; low level indoor fluorescent lighting; and dark storage with daily measurement under full sun simulation. Three nominally
identical devices were used in each experiment both to provide an assessment of the homogeneity of the samples and to distribute samples for
a variety of post soaking analytical measurements at six distinct laboratories enabling comparison at various stages in the degradation of the
devices. Characterization includes current-voltage curves, light beam induced current (LBIC) imaging, dark lock-in thermography (DLIT),
photoluminescence (PL), electroluminescence (EL), in situ incident photon-to-electron conversion efficiency (IPCE), time of flight secondary
ion mass spectrometry (TOF-SIMS), cross sectional electron microscopy (SEM), UV visible spectroscopy, fluorescence microscopy, and
atomic force microscopy (AFM). Over 100 devices with more than 300 cells were used in the study. We present here design of the device
sets, results both on individual devices and uniformity of device sets from the wide range of characterization methods applied at different
stages of aging under the three illumination conditions. We will discuss how these data can help elucidate the degradation mechanisms as well
as the benefits and challenges associated with the unprecedented size of the collaboration.
Insufficient lifetimes of organic photovoltaics are manifested in a reduced photovoltaic response, which is a consequence of physical and chemical degradation of the photovoltaic device. To prevent degradation it is vital to gain detailed insight into the degradation mechanisms. This is possible by utilizing state-of-the-art characterization techniques such as TOF-SIMS, XPS, AFM, SEM, interference microscopy and fluorescence microscopy as well as isotopic labeling (18O2 and H218O). By a combination of lateral and vertical analyses of the devices we obtain in-depth and in-plane information on the reactions and changes that take place in the various layers and interfaces. Examples will be presented that describe the advantages and disadvantages of various characterization techniques in relation to obtaining information on the degradation behavior of complete photovoltaic devices.
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