Transparent bifacial a-Si:H solar cells employing silver oxide embedded transparent rear electrodes for improved transparency

Abstract

We developed a transparent oxide–metal–oxide (OMO) structure using aluminum-doped zinc oxide and oxidized silver (AgOx) as a transparent electrode of a hydrogenated amorphous silicon (a-Si:H) thin-film solar cell for use in building-integrated photovoltaic (BIPV) windows. The oxygen (O2) addition (O2 flow rate) was optimized for a metal-to-dielectric intermediate-phase AgOx OMO to have high transparency and high conductivity, which were confirmed by finite-difference time-domain simulation. Using the AgOx OMO as a rear electrode, transparent a-Si:H solar cells were fabricated for BIPV window application. The performance of the fabricated cells showed highest bifacial efficiency (b-η) of 7.87% at AgOx OMO of 1 sccm, and highest average transmittance (T500–800, i.e., wavelength range: 500–800 nm) of 21.9% at AgOx OMO of 3 sccm, i.e., improvements from b-η = 7.42% and T500–800 = 18.8% at Ag OMO of 0 sccm. The cell with the optimized AgOx OMO (3 sccm) achieved b-η = 7.69% and the best figure of merit (product of b-η and T500–800) of 169%, i.e., 30% higher than the Ag OMO cell (139%). The developed AgOx OMO electrodes could be used in BIPV windows or in other optical devices requiring both high transparency and high conductivity.