ZnO Nanoparticle Layer Research Articles

Nucleation density and pore size tunable growth of ZnO nanowalls by a facile solution approach: growth mechanism and NO2 gas sensing properties.

Nanowalls are novel nanostructures whose 3D porous network morphology holds great potential for applications as gas sensors. The realization of such a nanowall-based gas sensor depends directly on the comprehensive understanding of the growth mechanism of the nanowalls. We induced nucleation density and pore size evolution by increasing the dipping and growth times. The investigation indicates that the 3D porous ZnO nanowalls consist of a seed layer of ZnO nanoparticles and a growth layer of the vertically grown ZnO nanosheets. The seed layer nucleation density dominance is driven by the dipping time. The pore size and the height of the as-grown ZnO nanowalls are determined by varying the growth time. Possible growth mechanisms governing the physical characteristics of the synthesized ZnO nanostructures in the solution process are proposed and discussed. The gas sensor that was fabricated from the ZnO nanowall structure exhibited strong dependence on the microstructure, which was mainly determined by the preparation conditions.

Preparation and Photocathodic Protection Properties of ZnO/TiO2 Heterojunction Film Under Simulated Solar Light.

In this work, a novel double layer made of ZnO nanorod arrays and TiO2 nanorod arrays with anticorrosion function were successfully prepared on fluorine-doped tin oxide (FTO) substrate by a simple low-temperature solvothermal method. As compared with the pure TiO2 and pure ZnO film, the combination of the two films presented higher photocathodic protection performance for 316 stainless steel (316 SS) and Q235 carbon steel in 3.5 wt% NaCl solution. The composite film with ZnO nanoparticles layer between ZnO nanorod arrays and TiO2 nanorod arrays exhibited the best photocathodic performance, which lowered the open circuit potential (OCP) of 316 SS and Q235 to −991 mV, −1066 mV, respectively. The results demonstrated that the formation of the uniform heterojunction film and the small difference in band alignment played important roles in the promotion of photocathodic protection performance.

Charge transfer improvement of ZnO-based dye-sensitized solar cells modified with graphite nanosheets and bilayer photoelectrode structures

In this work, dye-sensitized solar cells (DSSCs) were fabricated with different photoelectrode structures consisting of a ZnO-based photoelectrode, a ZnO/Au Schottky barrier-based photoelectrode, graphite nanosheets loaded on a ZnO (GZnO)-based photoelectrode, graphite nanosheets loaded on a ZnO nanoparticles (GZnO NPs)-based photoelectrode and graphite nanosheets loaded on a ZnO nanoparticles/ZnO (GZnO NPs/ZnO) as a bilayer-based photoelectrode. The photovoltaic characteristics of DSSCs were investigated based on: the power conversion efficiency (PCE), short-circuit current density (Jsc), open-circuit voltage and fill factor. The kinetics electron transport of DSSCs was carried out using electrochemical impedance spectroscopy (EIS). The semi-circle in the Nyquist plot was calculated to represent the charge transfer resistance (Rct). It was found that the GZnO NPs/ZnO bilayer-based photoelectrode exhibited the maximum Jsc (9.185 mA/cm2) and maximum PCE (2.37%), which resulted by the minimum Rct in the device. The result can be interpreted as showing that a graphite nanosheet structure improves the electron transport property which produces an excellent charge transfer mechanism in the photoelectrode. Accordingly, enhanced performance of ZnO-based dye-sensitized solar cells with graphite nanosheets loaded on a ZnO nanoparticles layer could be simply explained in terms of the charge transfer mechanism.

Impact of 1,2-ethanedithiol treatment on luminescence and charge-transport characteristics in colloidal quantum-dot LEDs

We report on a substantial increase in luminance and luminous efficiency of green-light emitting devices (LEDs) that use colloidal CdSe@ZnS quantum dots (QDs) as a light-emitting material in response to treatment with 1,2-ethanedithiol (EDT). The maximum luminance increased from 1146 to 8075 cd m−2, and luminous yield from 0.15 to 1.41 cd A−1 as a result of treating an incomplete device with drops of EDT right after spin-coating QDs onto a ZnO-nanoparticle layer. Based on systematic studies on substrate-dependent change in photoluminescence, and current-voltage and luminance–voltage characteristics, we propose that passivation of intra-gap defect states and relative shifts of energy levels relevant to the operation of QD LEDs are two main results of EDT treatment. In particular, we argue that energy-level shift without emission-color change can be attributed to surface-dipole effects.

Microwave-assisted Fe-doped ZnO nanoparticles for enhancement of silicon solar cell efficiency

We have investigated the performance of a silicon solar cell coated with ZnO nanoparticle layers doped with iron varying from (0–20%). We synthesized nanoparticles using a microwave method and fabricated thin film layers on silicon solar cells through a spin coating technique. The structure and morphology of nanoparticles were analyzed through transmission electron microscopy (TEM) and X-ray diffraction spectroscopy (XRD). The size of the particles decreased as iron concentration increased from 0 to 15%. Optical properties were analyzed through photoluminescence (PL) and absorption spectroscopy. PL spectra show a blueshift in the near band edge emission peaks for 0–15% doped samples and a redshift for the 20% doped sample. The band gap of Fe–ZnO nanoparticles (0–15%) was found to increase from 3.20 eV to 3.24 eV, and the bandgap decreased to 3.22 eV for 20% Fe–ZnO nanoparticles. Current-Voltage measurements confirm the enhancement in power conversion efficiency by 30% with iron doping in ZnO up to 15%. Efficiency increased with nanoparticle layers up to 180.29 nm in every sample and decreased with further increase in thickness. Enhancement in external quantum efficiency (EQE) was also observed with the increase in dopant concentration up to 15%. The optimum thickness of the ZnO nanoparticle layer was found to be approximately 180 nm for maximum enhancement in conversion efficiency.

3D printed zirconia ceramic hip joint with precise structure and broad-spectrum antibacterial properties.

Background: Nowadays, zirconia ceramic implants are widely used as a kind of hip prosthesis material because of their excellent biocompatibility and long-term wear resistance. However, the hip joint is one of the major joints with complex 3D morphological structure and greatly individual differences, which usually causes great material waste during the process of surgical selection of prosthesis.Methods: In this paper, by combining ceramic 3D printing technology with antibacterial nano-modification, zirconia ceramic implant material was obtained with precise 3D structure and effective antibacterial properties. Among which, two technical problems (fragile and sintering induced irregular shrinkage) of 3D printed ceramics were effectively minimized by optimizing the reaction conditions and selective area inversing compensation. Through in vivo and in vitro experiments, it was confirmed that the as prepared hip prosthesis could precisely matched the corresponding parts, which also exhibited good biocompatibility and impressive antibacterial activities.Results: 1) Two inherent technical problems (fragile and sintering induced irregular shrinkage) of 3D printed ceramics were effectively minimized by optimizing the reaction conditions and selective area inversing compensation. 2) It could be seen that the surface of the ZrO2 material was covered with a layer of ZnO nano-particles. A universal testing machine was used to measure the tensile, bending and compression experiments of ceramic samples. It could be found that the proposed ZnO modification had no significant effect on the mechanical properties of ZrO2 ceramics. 3) According to the plate counting results, ceramics modified with ZnO exhibited significantly higher antibacterial efficiency than pure ZrO2 ceramics, the ZrO2-ZnO ceramics had a significant killing effect 8 hours. 4) The removed implants and the tissue surrounding the implant were subjected to HE staining. For ZrO2-ZnO ceramics, inflammation was slight, while for pure ZrO2 ceramics, the inflammatory response could be seen that the antibacterial rate of the ZrO2-ZnO ceramics was significantly better than that of the pure ZrO2 ceramics group. 5) It could be seen that the cytotoxicity did not increase proportionally with the increase of concentration, all of viability were still above 80%. This suggested that our materials were safe and could be applied as a type of potential biomaterial in the future. 6) Further animal studies demonstrated that the implant was in good position without dislocation. This resulted implied that the proposed method can achieve accurate 3D printing preparation of ceramic joints. In addition, the femurs and surrounding muscles around the implant were then sectioned and HE stained. Results of muscle tissue sections further showed no significant tissue abnormalities, and the growth of new bone tissue was observed in the sections of bone tissue.Conclusion: 1) The ceramic 3D printing technology combined with antibacterial nano-modification can quickly customize the ideal implant material with precise structure, wear-resistant and effective antibacterial properties. 2) Two inherent technical problems (fragile and sintering induced irregular shrinkage) of 3D printed ceramics were effectively minimized by optimizing the reaction conditions and selective area inversing compensation. 3) ZnO nano-materials were modified on the ceramic surface, which could effectively killing pathogenic bacteria.

Construction of ZnO-Nanoflowers Photoanode for Photoelectrochemical Cell

ZnO-nanoflowers on a transparent conductive tin-doped In2O3 (ITO) glass substrate have been successfully prepared via a simple and efficient growth approach that is combining of dip coating and hydrothermal processes. One thin layer of ZnO nanoparticles is prepared by dip coating method followed by hydrothermally grown of ZnO nanoflowers at low temperature. The morphology and structure of ZnO-nanoflowers were inspected by field-emission scanning electron microscopy (FE-SEM) and X-ray diffraction (XRD), respectively. The optical absorption and photoluminescence spectra of ZnO-nanoflowers are also investigated. The ZnO-nanoflowers photoanode shows dramatically contributed to the separation of electron-hole pairs and enhanced the photoresponse. The photocurrent density is 0.44 mA/cm2 indicated that the PEC cells based on ZnO-nanoflowers photoanode have promising application potential in overall solar energy.

All‐solution‐processed transparent front contact for monograin layer kesterite solar cells

AbstractThe paper presents a fully solution‐processed transparent front contact for kesterite monograin layer solar cells, which is composed of a silver nanowire network above a ZnO‐based window bilayer. This window bilayer comprises a layer of ZnO nanoparticles and a second layer of chemical‐bath‐deposited doped ZnO. The optimized front contact can be processed within minutes and performs equally to a reference front contact with a sputtered iZnO/ZnO:Al window bilayer, both on solar cell and module level with sizes up to 20 × 20 cm2. To achieve this, it was necessary to obtain a compact morphology of the chemical‐bath‐deposited, doped ZnO film even for very short deposition times. It is found that, firstly, this depends on the homogeneity of the seed layer, which is the prerequisite for thin film growth by chemical bath deposition (CBD) on the substrate. It is shown that the ZnO nanoparticle layer covers the rough monograin substrate in a continuous and unperturbed manner. The second aspect of importance was the dopant type used in the CBD process (Al, Ga, or In). Optimal combination of photovoltaic performance and process speed was obtained for Ga‐doped ZnO, yielding compact films for deposition times as low as 1 minute. The solution‐processed window layers are susceptible to a light‐soaking effect, which impairs the cell performance upon storage in dark conditions. While this effect can be easily overcome in the laboratory, the effect in a real application scenario was investigated under outdoor conditions for a period of 4 weeks.

Oxygen annealing of the ZnO nanoparticle layer for the high-performance PbS colloidal quantum-dot photovoltaics

Though numerous researches regarding the influence of annealing atmospheric condition of ZnO have been carried out, the impact of annealing atmosphere on the carrier transporting properties and the performance of the ZnO-based optoelectronics has not been well-established. Here, the effects of annealing atmosphere (i.e., N2, ambient air, and O2) used to generate ZnO nanoparticle (NP) layers are elucidated. The chemical nature of ZnO layers, especially the amount of oxygen vacancies in ZnO NPs, is modulated by the annealing atmosphere. As the composition of O2 gas increases in the annealing atmosphere, a notable reduction of oxygen vacancies of ZnO NPs and electron mobility enhancement are observed, indicating that O2 gas contributes to a reduction of surface defects on ZnO NPs during the annealing process. In addition, trap-filling by reduced oxygen vacancies of air- and O2-annealed ZnO layers, induces the enhanced built-in potential in colloidal quantum-dot photovoltaic (CQDPV) devices. As expected, PbS CQDPVs with an air- and O2-annealed ZnO layer demonstrate significantly improved power conversion efficiencies than CQDPVs with an N2-annealed ZnO layer. Further analysis shows that the interfacial recombination is reduced for CQDPVs with an air- and O2-annealed ZnO layer due to the reduced trap states of ZnO NPs.

Colloidal-annealing of ZnO nanoparticles to passivate traps and improve charge extraction in colloidal quantum dot solar cells.

The popularity of colloidal quantum dot (CQD) solar cells has increased owing to their tunable bandgap, multiple exciton generation, and low-cost solution processes. ZnO nanoparticle (NP) layers are generally employed as electron transport layers in CQD solar cells to efficiently extract the electrons. However, trap sites and the unfavorable band structure of the as-synthesized ZnO NPs have hindered their potential performance. Herein, we introduce a facile method of ZnO NP annealing in the colloidal state. Electrical, structural, and optical analyses demonstrated that the colloidal-annealing of ZnO NPs effectively passivated the defects and simultaneously shifted their band diagram; therefore, colloidal-annealing is a more favorable method as compared to conventional film-annealing. These CQD solar cells based on colloidal-annealed ZnO NPs exhibited efficient charge extraction, reduced recombination and achieved an enhanced power conversion efficiency (PCE) of 9.29%, whereas the CQD solar cells based on ZnO NPs without annealing had a PCE of 8.05%. Moreover, the CQD solar cells using colloidal-annealed ZnO NPs exhibited an improved air stability with 98% retention after 120 days, as compared to that of CQD solar cells using non-annealed ZnO NPs with 84% retention.

Enhanced electron transport enables over 12% efficiency by interface engineering of non-fullerene organic solar cells

Organic solar cells have attracted much attention in the recent years due to their many intrinsic advantages, such as, light weight, flexibility, low-cost, solution processing, and facile device fabrication. In this study, effective interface engineering was employed to improve all the photovoltaic parameters of an organic solar cell simultaneously by incorporating ZnO nanoparticle (ZnO-NP) interlayer in between the indium tin oxide cathode and sol-gel processed ZnO electron transport layer. The significance of incorporating a ZnO-NP/ZnO bilayer as the electron transport layer in the bulk heterojunction organic solar cells was demonstrated via systematic study, employing a high efficiency photoactive layer system (PBDB-T:ITIC). The bilayer electron transport layer demonstrated reduced work function compared to the sol-gel ZnO, which enabled effective electron transfer from the active layer to the electron transport layer. In addition, improved bilayer surface morphology, via reduction of ZnO-NP layer roughness, and better crystallinity compared to sol-gel ZnO facilitated charge separation and transmission between electron transport layer and active layer. Consequently, the devices with bilayer interlayer exhibited an enhancement of > 13% in power conversion efficiency compared to the control devices with sol-gel only ZnO as electron transport layer. The mechanisms behind the improvement in device performance were analysed using the ultraviolet and X-ray photoelectron spectroscopy and electrochemical impedance spectroscopy. The champion bilayer device exhibited 12.24% efficiency which is much higher than the efficiency of 10.69% for the control device.

Improved charge carrier transfer in squaraine-capped ZnO nanoparticles layer for electron transport of hybrid solar cells

Blend of conjugated polymer poly(3-hexylthiophene) or P3HT and Zinc Oxide nanoparticles (ZnO-NPs) has been intensively used as active material for high performance hybrid solar cells. However, agglomeration of ZnO-NPs hinders efficient charge carrier or charge transfer both from P3HT to ZnO-NPs and its transport within ZnO-NPs which lead to low performance of solar cells. Capping of ZnO-NPs is currently applied to avoid this agglomeration effect. In this study, we used small molecule squaraine (SQ) to cap ZnO-NPs. SQ was chosen due to its lowest unoccupied molecular orbital (LUMO) level lower than conduction band of ZnO, therefore, SQ can assist charge transfer to ZnO-NPs. Moreover, SQ molecule also enhances light absorption due to its high light absorption in the near infrared region and large spectral overlap between the P3HT emission and SQ absorption. Here we report our current study on charge carrier transport in the blend of P3HT and SQ-capped ZnO-NPs by using photoluminescence spectroscopy with UV and blue excitation wavelengths. ZnO-NPs were synthesized by using sol-gel method. The capping process was employed by mixing small amount of SQ solution into the ZnO-NPs gel before its blend with P3HT. Small molecule SQ was successfully capped ZnO-NPs as observed from its TEM image. ZnO-NPs solution has absorption wavelength less than 380 nm, therefore, no emission spectrum is observed when it is excited with 473 nm excitation wavelength. However, a clear emission spectrum is observed from SQ-capped ZnO-NPs solution, which shows that charge transfer was occurred from SQ to ZnO-NPs. Similar behavior was also observed in the blend of P3HT and SQ-capped ZnO-NPs. Our study shows that small molecule squaraine can improve charge carrier transfer from ZnO-NPs and therefore the performance of solar cells might be increased.

Highly stable QLEDs with improved hole injection via quantum dot structure tailoring

For the state-of-the-art quantum dot light-emitting diodes, while the ZnO nanoparticle layers can provide effective electron injections into quantum dots layers, the hole transporting materials usually cannot guarantee sufficient hole injection owing to the deep valence band of quantum dots. Developing proper hole transporting materials to match energy levels with quantum dots remains a great challenge to further improve the device efficiency and operation lifetime. Here we demonstrate high-performance quantum dot light-emitting diodes with much extended operation lifetime using quantum dots with tailored energy band structures that are favorable for hole injections. These devices show a T95 operation lifetime of more than 2300 h with an initial brightness of 1000 cd m−2, and an equivalent T50 lifetime at 100 cd m−2 of more than 2,200,000 h, which meets the industrial requirement for display applications.

Spectrum Selectivity and Responsivity of ZnO Nanoparticles Coated Ag/ZnO QDs/Ag UV Photodetectors

Photoresponsivity and spectrum selectivity of ZnO nanoparticles (NPs)-coated colloidal quantum dots (CQDs)-based Ag/ZnO QDs/Ag interdigitated metal-semiconductor-metal (MSM) photodetectors under front and back illuminations have been investigated in this letter. It is shown that the ZnO NPs film coated over the interdigitated MSM photodetector acts as a filter layer to enhance the spectrum selectivity at the cost of reduced responsivity of the detector under front illumination. Whereas, the same NPs layer acts as a scattering medium to enhance the responsivity at the cost of reduced selectivity of the detector under back illumination condition. The measured responsivity under front illumination is 6 A/W with a full width at half maxima (FWHM) of ~25 nm, whereas it is increased to 20 A/W with an FWHM of ~49 nm under back illumination at an applied bias of 2 V. Thus, the ZnO NPs layer can be used to optimize the photoresponse characteristics of the ZnO CQDs-based MSM photodetector by changing the direction of illumination on the device.

Fully solution processed semi-transparent perovskite solar cells with spray-coated silver nanowires/ZnO composite top electrode

Semi-transparent perovskite solar cells with spray coated silver nanowire (AgNW) and AgNW/ZnO composite top electrode were fabricated and investigated. For the spray coated AgNW electrode, both sheet resistance (Rs) and averaged visible light transmittance over 400–800 nm (AVT) decrease with the decrease of nozzle moving speed, which is ascribed to the increase of AgNW density of the electrode. A highest power conversion efficiency (PCE) of 13.27% with a low AVT of 16.3% was achieved for a small area cell having AgNW top electrode with Rs of 15 Ω/□. A thin layer of ZnO nano particles was coated onto the AgNW electrode, which decreases the sheet resistance of the AgNW/ZnO composite electrode. Such a conductivity enhancement is ascribed to the improvement the interconnection between AgNWs by filling the voids between AgNW wires with ZnO nanoparticles. In the meanwhile, owing to the light scattering effect of ZnO nano particles, light transparence in the visible light range (400–800 nm) of the AgNW/ZnO composite electrode increases slightly after the deposition of ZnO layer. Both device performance and reproducibility of the perovskite solar cells are improved by using the AgNW/ZnO top electrode. As an example, power conversion efficiency of 7.30% with an AVT of 23.3% was achieved for a small solar cell using AgNW electrode with Rs of 78 Ω/□. While a highest PCE of 11.13% with the same AVT was achieved for the same cell after the deposition of ZnO layer, demonstrating the cover effect of ZnO layer. A high PCE of 8.18% was also achieved for a AgNW/ZnO based cell with an area of 1 cm2, which is more than 50% enhancement than the AgNW based cell (5.35%).

Suppressed Interfacial Charge Recombination of PbS Quantum Dot Photovoltaics by Graphene Incorporated into ZnO Nanoparticles.

Single-layer graphene (SLG) was incorporated into ZnO nanoparticles (NPs), and use of this material in photovoltaic devices generated significant changes. The Fermi level of ZnO NPs underwent a downshift, whereas the conduction and valence bands were maintained with increasing SLG concentrations. Furthermore, the effective defect densities were reduced and carrier mobility was enhanced. Colloidal quantum dot photovoltaics (CQDPVs) with the SLG-incorporated ZnO NP layer as an electron transporting layer achieved significant performance enhancement. Poor performing CQDPVs were also observed with incorporation of an excess amount of SLG. This trend paralleled the interfacial charge recombination trends of CQDPVs. Effective suppression of interfacial recombination was achieved for CQDPVs with an appropriate SLG concentration, whereas dramatically increased interfacial recombination was observed for CQDPVs with an excess of SLG. For CQDPVs with appropriate SLG incorporation, efficient defect passivation and enhanced electron mobility of ZnO NPs facilitated loss-less electron transfer and efficient electron extraction without compromising the favorable energy level alignment. Excess SLG incorporation led to an increase in recombination within the PbS QD layer due to the presence of an energy barrier. This simple and powerful strategy provides an effective method for modulating the interfacial properties of CQDPVs.

Low-temperature solution processed flexible silver nanowires/ZnO composite electrode with enhanced performance and stability

Silver nanowires (Ag NWs) network is considered a promising alternative to replace indium tin oxide (ITO) as transparent conductive electrode (TCE). However, there are several intrinsic shortcomings such as rough surface topography, poor ambient and thermal stability still restrict their practical application. Here, we demonstrated a low temperature solution-processed composite TCE comprising of Ag NWs and ZnO nanoparticles (NPs) could resolve above issues. The highest temperature in whole process is no more than 100 °C. By optimizing the density of Ag NWs together with the thickness of ZnO NPs layer, the composite TCE showed excellent flexibility, ambient and thermal stability (∼300 °C) as well as high electrical conductivity (∼20 Ω/sq) and good optical transparency (∼87% at 550 nm). In addition, the ZnO NPs capping layer reduced the surface roughness of Ag NWs network by more than half of its initial value. All the demonstrated properties show the Ag NWs/ZnO composite TCE would be an ideal choice in a variety of flexible optoelectronic devices.

Synthesis and Characterization of Antireflective ZnO Nanoparticles Coatings Used for Energy Improving Efficiency of Silicone Solar Cells

The paper proposes a new and complex process for the synthesis of ZnO nanoparticles for antireflective coating corresponding to silicone solar cells applications. The process consists of two major steps: preparation of seed layer and hydrothermal growth of ZnO nanoparticles. Due to the fact that the seed layer morphology influences the ZnO nanoparticles proprieties, the process optimization of the seed layer preparation is necessary. Following the hydrothermal growth of the ZnO nanoparticles, antireflective coating of silicone solar cells is achieved. After determining the functional parameters of the solar cells provided either with glass or with ZnO, it is concluded that all the parameters values are superior in the case of solar cells with ZnO antireflection coating and are increasing along with the solar irradiance.

Efficient dye-sensitized solar cells from mesoporous zinc oxide nanostructures sensitized by N719 dye

Dye-sensitized solar cells (DSCs) have attracted a great deal of attention due to their low-cost and high power conversion efficiencies. They usually utilize an interconnected nanoparticle layer of TiO2 as the electron transport medium. From the fundamental point of view, faster mobility of electrons in ZnO is expected to contribute to better performance in DSCs than TiO2, though the actual practical situation is quite the opposite. In this research, we addressed this problem by first applying a dense layer of ZnO on FTO followed by a mesoporous layer of interconnected ZnO nanoparticle layer, both were prepared by spray pyrolysis technique. The best cell shows a power conversion efficiency of 5.2% when the mesoporous layer thickness is 14 μm and the concentration of the N719 dye in dye coating solution is 0.3 mM, while a cell without a dense layer shows 4.2% under identical conditions. The surface concentration of dye adsorbed in the cell with a dense layer and that without a dense layer are 5.00 × 10−7 and 3.34 × 10−7 mol/cm2, respectively. The cell with the dense layer has an electron lifetime of 54.81 ms whereas that without the dense layer is 11.08 ms. As such, the presence of the dense layer improves DSC characteristics of ZnO-based DSCs.

Interplay of Interfacial Layers and Blend Composition To Reduce Thermal Degradation of Polymer Solar Cells at High Temperature.

The thermal stability of printed polymer solar cells at elevated temperatures needs to be improved to achieve high-throughput fabrication including annealing steps as well as long-term stability. During device processing, thermal annealing impacts both the organic photoactive layer, and the two interfacial layers make detailed studies of degradation mechanism delicate. A recently identified thermally stable poly[[4,8-bis[(2-ethylhexyl)oxy]benzo[1,2-b:4,5-b']dithiophene-2,6-diyl][3-fluoro-2-[(2-ethylhexyl)carbonyl]thieno[3,4-b]thiophenediyl]]:[6,6]-phenyl-C71-butyric acid methyl ester (PTB7:PC70BM) blend as photoactive layer in combination with poly(3,4-ethylenedioxythiophene) polystyrene sulfonate as hole extraction layer is used here to focus on the impact of electron extraction layer (EEL) on the thermal stability of solar cells. Solar cells processed with densely packed ZnO nanoparticle layers still show 92% of the initial efficiency after constant annealing during 1 day at 140 °C, whereas partially covering ZnO layers as well as an evaporated calcium layer leads to performance losses of up to 30%. This demonstrates that the nature and morphology of EELs highly influence the thermal stability of the device. We extend our study to thermally unstable PTB7:[6,6]-phenyl-C61-butyric acid methyl ester (PC60BM) blends to highlight the impact of ZnO on the device degradation during annealing. Importantly, only 12% loss in photocurrent density is observed after annealing at 140 °C during 1 day when using closely packed ZnO. This is in stark contrast to literature and addressed here to the use of a stable double-sided confinement during thermal annealing. The underlying mechanism of the inhibition of photocurrent losses is revealed by electron microscopy imaging and spatially resolved spectroscopy. We found that the double-sided confinement suppresses extensive fullerene diffusion during the annealing step, but with still an increase in size and distance of the enriched donor and acceptor domains inside the photoactive layer by an average factor of 5. The later result in combination with comparably small photocurrent density losses indicates the existence of an efficient transport of minority charge carriers inside the donor and acceptor enriched phases in PTB7:PC60BM blends.