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Fabrication of Perovskite Solar Cells & Applications in Multijunction Configurations

Hosseinian Ahangharnejhad, Ramez
http://orcid.org/0000-0003-1398-0397
http://rave.ohiolink.edu/etdc/view?acc_num=toledo1575980394222122

Abstract Details

2019, Doctor of Philosophy, University of Toledo, Physics.
With growing energy demands, renewable energy technologies, and particularly photovoltaics (PV), are becoming more relevant for future large-scale deployment. While the current stage of PV field is growing at the highest pace with respect to other forms of energy resources, the quest to achieve higher solar power conversion efficiencies (PCE) at lower cost is still continuing. To this end, the search for PV technologies and structures that are robust, efficient and cost effective have brought the field of emerging PV to respond to shortcomings of Si based and also the 2nd generation PV technologies (e.g. CdTe or CuInGaSe2 (CIGS)). One of the most successful forms of emerging or 3rd generation PV has been demonstrations of metal halide perovskite PV. While perovskites have been remarkable in achieving high PCEs (< 25%) in the span of one decade, they possess properties that allow for more novel approaches in structures and fabrication. The potential to reduce costs further with roll to roll manufacturing, due to solution processability of perovskites, raises the possibility of fabrication on flexible substrates or semitransparent devices. All of these contribute to potential of these devices for variety of applications. In the meantime, the possibility of bandgap engineering in perovskites without significant compromise in PCE has brought up another field of possibility which involves the applications of perovskites in multijunction or tandem structures. Demonstrations of tandem devices with perovskite subcells have been made by pairing these devices with CIGS, Si and other prominent PV technologies. To further understand the limitation of device performances particularly from the prospect of optics, in this thesis, a model based on transfer matrix method was developed. Using this approach, the optics of multi-layer stack in the structure of tandem device is analyzed and clear recipes on the bandgap and thickness of perovskite subcell to maximize the performance of tandem devices are developed. By expanding on the optical modelling approach to involve the device current-voltage behavior we offer a more detailed PCE analysis on the perovskite/CIGS tandem devices. While the PCEs analysis provide critical insights towards fabrication of devices, the performances of these tandem devise under real world conditions would be of importance for future applications. To this end we further developed our model to include the angular incident light and module temperature to simulate the annual energy yield (AEY) for perovskite/CIGS tandem devices under real world conditions. For these analyses we used hourly data provided by National Renewable Energy Laboratory for solar diffuse horizontal and direct normal irradiance components of solar irradiance in multiple locations with calculated angles of incident for stand-still, 1-axis and 2-axis tracking conditions. Coupled to these we also incorporated the atmospheric hourly data to calculate the module temperatures at each of these conditions. By introducing variation into bandgaps of top and bottom subcells we offer a comprehensive analysis into AEY of perovskite/CIGS tandems in two and four-terminal configurations. We also show that the device performances under real world conditions are slightly different than the expectations from the normal incident laboratory conditions PCE simulations. However, these devices can be more forgiving in AEY by allowing a large spectral overlap using appropriate thickness control in top perovskite subcell. While findings of AEY point out the potential of perovskite/CIGS tandem devices, the actual applicability of these devices would be questionable due to higher cost of fabrication. To investigate the economic viability of perovskite/CIGS tandem devices we study the levelized cost of electricity (LCOE) for these devices using the AEY results and compare them to single junction perovskite and CIGS devices. The cost associated with each technology and configuration is calculated by introducing a bottom up cost model which incorporates step by step manufacturing cost for each structure in addition to operational and financial costs. The LCOE findings show values as low as ~ 4 ¢.(kW.h)-1 for tandem structures at locations with significant annual solar irradiance. While AEY results point out improvements due to tracking, the viability of such systems is a matter of cost associated with them. To analyze the viability of tracking we also incorporate an additional cost value to due to tracking as a percentage of manufacturing and operational costs. By varying the additional cost percentage due to tracking we analyze the LCOE of tracked systems and we compare them to standstill modules. Results of lowest LCOE under varying conditions show that the 1-axis and 2-axis tracking systems are better options if the additional cost is within approximately 20% and 40% of standstill cases respectively. Another scenario where viability of tandem structures over single junction modules can be ambiguous is the faster degradation in one subcell compared to the other. To this end we perform LCOE analysis over tandem devices with varying subcell lifetime and by comparing them to those of single junction devices we determine the window of economic viability for tandem devices. To study the uniformity of current generation across a PV device, laser beam induced current (LBIC) has been shown to be a powerful method of characterization. To improve the resolution limit of this method to determine feature sizes smaller than the laser beam dimensions we introduce a novel approach. In this approach we convolute the laser beam intensity profile and the device spatial current generation capability to simulate the LBIC signal. To determine the feasibility of this method we apply it to LBIC measurements performed across laser scribe lines on a thin film device. We introduce the laser scribe lines as square shaped trenches in to the device profile and perform the simulations. Using this we approach we determine the width of electronic damage induced in the devices as result of laser scribing. We show that the scale of such damage varies as function scribing laser power which is directly associated with the difference in the electronic damage and material ablation thresholds of the scribing laser power. One of the challenges associated with large scale application of perovskite devices is the low stability of these devices to environmental conditions such as humidity. We use LBIC to determine the lifetime of devices as we expose them to humidity. In this approach, as the moisture reacts with the perovskite device the current generation diminishes. To improve the device resistance to humidity we use conformal deposition of SiO2 thin films on devices. LBIC measurements show that the devices degradation rate significantly reduces as they are encapsulated. We also show that by increasing the encapsulation layer thickness the lifetimes increase. While for certain perovskite compositions the devices degrade entirely in an hour under extreme humid conditions by usage of 45 nm and 300 nm encapsulation layer these time scale improve to 10 hours and over 48 hours respectively.
Michael Heben, PhD (Advisor)
Robert Collins, PhD (Committee Member)
Yanfa Yan, PhD (Committee Member)
Sanjay Khare, PhD (Committee Member)
Glenn Lipscomb, PhD (Committee Member)
177 p.
Condensed Matter Physics; Energy; Materials Science; Optics; Physics
Photovoltaics, Renewable energy, Thin film optics, Metal halide perovskites

Recommended Citations

Citations

  • Hosseinian Ahangharnejhad, R. (2019). Fabrication of Perovskite Solar Cells & Applications in Multijunction Configurations [Doctoral dissertation, University of Toledo]. OhioLINK Electronic Theses and Dissertations Center. http://rave.ohiolink.edu/etdc/view?acc_num=toledo1575980394222122

    APA Style (7th edition)

  • Hosseinian Ahangharnejhad, Ramez. Fabrication of Perovskite Solar Cells & Applications in Multijunction Configurations. 2019. University of Toledo, Doctoral dissertation. OhioLINK Electronic Theses and Dissertations Center, http://rave.ohiolink.edu/etdc/view?acc_num=toledo1575980394222122.

    MLA Style (8th edition)

  • Hosseinian Ahangharnejhad, Ramez. "Fabrication of Perovskite Solar Cells & Applications in Multijunction Configurations." Doctoral dissertation, University of Toledo, 2019. http://rave.ohiolink.edu/etdc/view?acc_num=toledo1575980394222122

    Chicago Manual of Style (17th edition)

toledo1575980394222122
133
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This open access ETD is published by University of Toledo and OhioLINK.