- Title
- Optimisation of aqueous solar nanoparticle inks for roll to roll fabrication of organic photovoltaics
- Creator
- Almyahi, Furqan A.
- Relation
- University of Newcastle Research Higher Degree Thesis
- Resource Type
- thesis
- Date
- 2019
- Description
- Research Doctorate - Doctor of Philosophy (PhD)
- Description
- The current study of this work presents an optimised approach of transferring nanoparticle organic photovoltaics (NP-OPVs) from laboratory (using spin-coating) to large-scale using roll to roll (R2R) technique. However, there have been few reports into the R2R processing of aqueous solar nanoparticle (ASNP) inks to fabricate large-scale devices. In this thesis, three studies have been addressed prior to R2R fabrication of OPV devices with ASNP inks. The first study was to explore the effects of transitioning from a small-scale bulk heterojunction (BHJ) ink formulated from a high-cost acceptor to a large-scale NP ink formulated from a low-cost fullerene mixture. The efficiency of ICxA devices was reduced by 10 % of the efficiency of PCBM devices due to a slightly reduction in P3HT crystallites. The P3HT:ICxA based nanoparticles consist functionally of a core shell internal morphology with a core consisting primarily of ICxA and P3HT being present predominantly in the shell. The P3HT:ICxA NP OPV devices based on large scale ink formulation were optimised by comparing to those of based on laboratory scale ink formulation. When lowering the concentration of the organic phase during ink preparation, devices based on laboratory and large scale inks had an equivalent device performance (PCE~0.9 %) despite of the application of different purification techniques. Upscaling of ink formulation was further optimised by controlling SDS concentrations by varying the dilution factor of ASNP inks for two purification processes: centrifugal and crossflow ultrafiltration processes. The crossflow process was found to have a lower efficiency for removing free-SDS than centrifugal process, as monitored by UV-vis spectroscopy and surface tension measurements of the ASNP ink filtrate. The SEM with EDX measurements and AFM images proved that the presence of the SDS crystallites on the ASNP film surfaces, and the SDS crystallites were decreased by increasing the dilution factor for both processes. The NP devices for both processes were fabricated and optimised as a function of dilution factor or surface tension, and the wetting properties of NP inks highly influences the device performance. The device performance increased with increasing dilution factor or surface tension (decreasing free-SDS) up to an optimal value (Peak PCE), after which a decrease in device performance was observed this was ascribed to poor wetting properties of NP inks. Centrifugal-based devices showed a peak PCE for NP inks with dilution factor of 57 while the similar peak PCE for crossflow-based devices was at dilution factor of 514. The peak PCE for both processes occurred for similar surface tension values of 48.1 and 48.8 mN m−1 (similar wetting properties). The second study focused on the effect of interlayers as an electron transport layer for NP devices driven by the impracticality of utilising calcium evaporation during R2R production. This study measured the sustainability of NP or BHJ devices to various interlayers (calcium, ZnO). Both NP and BHJ devices had a better performance when replacing calcium with solution processed ZnO interlayers. The impact of various green solvents (ethanol, methanol, IPA and acetone) on the performance of NP devices were characterised. The NP devices with ZnO interlayers fabricated from ethanol showed the highest performance. Optimising ZnO interlayer thickness further improved the performance of NP devices. With ZnO interlayers, a clear increase in the JSC was observed for BHJ devices while both the fill factor and JSC were increased for NP devices. NP devices with a ZnO interlayer show clear enhancements in device performance compared to devices with calcium interlayers, which formed a less mobile layer at the NP layer/calcium interface. Charge carrier mobility for the NP device with ZnO increased and its charge carriers were extracted in a short time while lifetime and charge carrier recombination were equivalent for the devices with both interlayers. NP devices with calcium interlayers exhibited high capacitance due to the effect of SDS ions at the NP layer/interlayer interface. In contrast, NP devices with ZnO as interlayer showed similar capacitance values as BHJ devices with calcium due to restriction of SDS ions migration by ZnO. The third study involved the optimisation of hole transport layers for NP devices by employing UVO treatment for various times on three types of PEDOT:PSS interlayer (Al4083, HTL Solar and PH1000). Influence of the UVO duration on PEDOT:PSS layers and its effect on NP films were examined, and the results showed there is a clear significant difference in the wetting properties of NP in UVO-treated layers in comparison to untreated layers. The device performance of treated device increased with optimal increasing UVO duration (with optimal values of: 10 min for Al4083, and 5 min for HTL Solar and PH1000) with lower device performance at higher UVO times. Finally, this thesis investigate the ability to applying corona treatment on PH1000 electrodes to R2R processing of ASNP inks for the fabrication of large-scale NP devices. The direct transfer for NP inks succeeded to produce low-performance devices due to a presence of high SDS concentrations while it was failed with low SDS inks. By contrast, large-scale NP devices based on low SDS inks were fabricated and optimised by corona treating PH1000 electrodes for various intensities. The R2R-printed NP devices showed a device performance of 0.45 % with increasing corona intensity. This thesis introduces the first NP module with an area of 21.6 cm2 and investigates the impact of encapsulation as well as thermal annealing on its performance. The PCE of NP module was increased to 0.42 % by applying both UV barrier encapsulation and thermal annealing, in addition to a slow light degradation for this module. Finally, this thesis highlights the requirements for producing large-scale nanoparticle devices in the future work.
- Subject
- organic photovoltaics; aqueous solar nanoparticle inks; roll to roll fabrication; purification techniques; UV ozone and corona treatment
- Identifier
- http://hdl.handle.net/1959.13/1400441
- Identifier
- uon:34771
- Rights
- Copyright 2019 Furqan A. Almyahi
- Language
- eng
- Full Text
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