Barrier height enhancement in heterojunction Schottky-barrier solar cells

Abstract

Significant enhancement of the open-circuit voltage (V <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">oc</inf> ) for GaAs Schottky-barrier solar cells has been achieved by inserting a thin AlGaAs barrier layer between the GaAs and metal surface layer. The maximum V <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">oc</inf> measured at 1 SUN AM1 for one of these structures is 0.88 V (compared to ≤ 0.5 V for conventional GaAs Schottky-barrier cells). At this illumination, a peak conversion efficiency of 10.5 percent was measured without antireflective (AR) coating from a structure of Au/Al <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0.5</inf> Ga <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0.5</inf> As/GaAs. High efficiency for this structure is achieved by minimizing the hole barrier to photogenerated carriers at the AlGaAs/GaAs interface. The model proposed for this type of structure indicates that AlGaAs composition, layer thickness, and GaAs doping density are the device parameters most strongly controlling cell performance.