Cracked Film Lithography with CuGaO x Buffers for Bifacial CdTe Photovoltaics

Bifacial CdTe solar cells with greater power density than the monofacial baselines are demonstrated by using a CuGaO rear interface buffer that passivates while reducing sheet resistance and contact resistance. Inserting CuGaO between the CdTe and Au increases mean power density from 18.0 ± 0.5 to 19.8 ± 0.4 mW cm for one sun front illumination. However, coupling CuGaO with a transparent conductive oxide leads to an electrical barrier. Instead, CuGaO is integrated with cracked film lithography (CFL)-patterned metal grids. CFL grid wires are spaced narrowly enough (≈10 µm) to alleviate semiconductor resistance while retaining enough passivation and transmittance for a bifacial power gain: bifacial CuGaO /CFL grids generate 19.1 ± 0.6 mW cm for 1 sun front + 0.08 sun rear illumination and 20.0 ± 0.6 mW cm at 1 sun front + 0.52 sun rear-the highest reported power density at field albedo conditions for a scaled polycrystalline absorber.