Three dimensionally structured thin film photovoltaic devices based on interdigitated arrays of microscale electrodes are examined. This geometry eliminates front contacts and window layers enabling absorption of the full solar spectrum by semiconductor materials deposited on the prefabricated metal comb structure. In contrast to Si thick film back contact solar cells, the electrodes in this design penetrate the bulk of the absorber with pitches comparable to the carrier diffusion lengths to decouple photon absorption and carrier diffusion, similar to nanopillar constructs. Initial electrodeposited CdS/CdTe heterojunction devices approach 1% efficiencies with simulations indicating significant potential for improvement based on external quantum efficiencies. Several electrode parameters, pitch, width, height, and material were experimentally probed and modeled. Suboptimal performance is attributed to contact reactivity and Schottky barrier formation due to the complementary Pt contacts. Although electrode differentiation requires a selective technique such as electrodeposition, the test bed structures and subsequent absorber synthesis processes are amenable to an array of deposition techniques for fabrication and measurements of three dimensionally structured semiconductors, contact materials and photovoltaic devices.
Citation: Progress in Photovoltaics
Pub Type: Journals