Thesis Defence: Perovskite-Cu(In, Ga)(S, Se)2 Tandem Solar Cells with Solution-Processed Absorbers
August 4 at 9:00 am - 1:00 pm
Katherine Latosinsky, supervised by Dr. Alexander R. Uhl, will defend their thesis titled “Perovskite-Cu(In, Ga)(S, Se)2 Tandem Solar Cells with Solution-Processed Absorbers” in partial fulfillment of the requirements for the degree of Master of Applied Science in Electrical Engineering.
An abstract for Katherine Latosinsky’s thesis is included below.
Defences are open to all members of the campus community as well as the general public. This examination will be offered in hybrid format. Registration is not required to attend in person, but please email alexander.uhl@ubc.ca to receive the Zoom link for this defence.
Abstract
Emergent organic-metal-halide perovskite solar cells have great potential for use in high efficiency tandem solar cell architectures, which incorporate a wide- and narrow-bandgap semiconductor to absorb a broader spectrum of light than conventional single-junction solar cells. The combination of wide-bandgap (~ 1.6-1.7 eV) perovskite and narrow-bandgap (~1.0 -1.1 eV) copper-indium-gallium-(sulfur)-selenide (CIGS) solar cells can be a foundation for lightweight, flexible thin-film tandem photovoltaics, creating new applications for solar electricity generation. The capacity to fabricate both solar cell absorbers with low-cost, high-throughput solution-based manufacturing could also make perovskite-CIGS tandem technology cost-competitive with market-dominant crystalline-silicon photovoltaics.
This thesis experimentally investigates the potential of perovskite-CIGS tandem solar cells with solution-processed absorbers, with a focus on optimizing the perovskite top-cell. A process is developed to fabricate wide-bandgap p-i-n perovskite solar cells with solution-based absorber and charge transport layers, which are suited for use in both monolithic and mechanically-stacked tandem architectures. A radio-frequency sputtering process is developed to deposit indium-tin-oxide (ITO) electrodes with adequate transparency and conductance, as quantified with UV-vis-NIR spectroscopy and four-point probe sheet resistance measurements. The performance of opaque devices with silver electrodes is compared to transparent devices with ITO electrodes using current-voltage and external quantum efficiency measurements.
The performance of the semi-transparent devices is shown to be limited by damage from ITO sputtering, which could be addressed by implementing suitable buffer-layers and/or a reduced energy sputter process. A comparison of semitransparent device performance when illuminated through the hole- or electron- transport layers reveals that the latter causes significant parasitic absorption losses in the sputtered ITO electrode, which poses a distinct challenge for developing
monolithic two-terminal tandems. Finally, the performance of mechanically-stacked four-terminal tandems is investigated using solution-based CIGS solar cell illuminated through an optical filter equivalent to the perovskite device-stack. The tandem devices achieve 9.3% power conversion efficiency with the sputter damaged perovskite cells, but show potential to approach 20% efficiency once sputter damage is mitigated.
