Extracting interface recombination velocities from double-heterojunction solar cell reverse-recovery characteristics

Silicon double heterojunction (DH) solar cells represent a possible future path for high-efficiency, low-cost solar power. These cells forgo doped p-n and n⁺-n (or p⁺-p) homojunctions diffused at ∼900 °C in favor of < 200 °C-deposited selective heterojunction contacts, which block one type of carrier while allowing the other to pass freely[1]. One heterojunction injects minority carriers (blocking majority carriers), and the other blocks minority carriers to reduce dark current (Fig 1). The efficiency of these cells is highly dependent on the interface quality of their heterojunctions. To date there is no method that uses reverse recovery (RR) transients to extract the actual interface characteristics from finished devices - methods like pulsed photoconductivity used on test samples cannot be extended to final devices with 2 metallized interfaces. Here, we give a procedure for the independent extraction of interface parameters at both heterojunctions.