High-temperature post-annealing effect on the device performance of B-doped p-type BaSi2/n-Si heterojunction solar cells grown by molecular beam epitaxy

Abstract

Astract We fabricated B-doped p-BaSi2/n-Si heterojunction solar cells by molecular beam epitaxy, and performed post-annealing at 1000 °C in an Ar atmosphere for various annealing durations (t a) in the range 15–300 s. At t a = 15 s, the conversion efficiency (η) under AM 1.5 G illumination was degraded unexpectedly from η = 1.96% for the as-grown sample to η = 0.8%. At t a ≥ 30 s, improvement of the open-circuit voltage (V OC) was obtained. V OC was increased from 0.28 V for the as-grown sample to 0.45 V at t a = 30 s, and the η reached 5.1%. Deep level transient spectroscopy measurement indicated the presence of hole traps coming from point defects near the BaSi2/Si interface. The surface morphology remained almost unchanged at t a ≤ 60 s. However, part of the surface peeled off at t a ≥ 120 s when we separated the attached samples from each other.