Point contact structures for Thin Film Solar Cells

Abstract

UltrathinCu(In,Ga)Se2(CIGS) has an immense potential to expand the application spectrum of photovoltaic technologies, such as Building Integrated Photovoltaics (BIPV) or as thepower source Internet of Things devices, due to its high efficiency, flexibility, stability and low-cost. However, since the low-coststems from a absorber thickness reduction, ultrathin CIGSfaces some challenges that are not present in standard thickness CIGS, such as a decreased lightabsorption and degraded electrical performance.This thesis is focused on the development and fabrication of mitigation strategies throughthe use of rear passivation and optically enhancing structures fabricated by several e-beamlithography steps. Due to the elemental diffusion and detrimental reactions with selenium, theencapsulation of the optically enhancing rear reflector ensures that the CIGS absorber will notbe negatively affected, while simultaneously increasing the photocurrent generation. Addition-ally, the rear passivation dielectric layer reduces the recombination velocity of the Mo/CIGSinterface and, consequently, increased the open circuit voltage. In addition to the fabricationand characterization of solar cells with an encapsulated passivation layer, these modificationswere studied with optical and electrical simulations and delivered a 3.2 % absolute efficiencyincrease.