Conversion efficiency improvement of InGaN/GaN multiple-quantum-well solar cells with Ex Situ AlN nucleation layer

The crystal quality, electrical, and optical characteristics of GaN solar cells (SCs) were improved using ex situ AlN nucleation layer. Replacing the in situ GaN nucleation layer with the sputtered ex situ AlN nucleation layer reduced the total dislocation density of GaN layer from 3.7 × 10⁸ to 2.2 × 10⁸ cm^-2. The dislocation density reduction of GaN with sputtered ex situ AlN nucleation could suppress the reverse leakage current and the forward recombination current in low forward voltage range of SCs, and thus can increase shortcircuit current density ( J_sc) and open-circuit voltage (Voc) of the SCs. A 1-sun power conversion efficiency (η%) of SCs with ex situ AlN nucleation (1.89%) showed an enhancement of 26% compared with that of conventional SC (1.50%). Furthermore, the 100-sun η% of SCs with ex situ AlN nucleation (1.97%) showed 18% improvement compared with that of conventional SC (1.67%).