Substrate-free large gap InGaN solar cells with bottom reflector

In this study, we report on the realization of the In_0.085Ga_0.915N p-i-n solar cell by low-pressure metalorganic vapor phase epitaxy (MOVPE). The w-2θ scans of (0 0 0 2) reflection observation indicate good suppression of phase separation for the p-i-n solar cells with a 150-nm-thick i-In_0.085Ga_0.915N epilayer. The sharp and narrow signals in the photoluminescence spectra of In_0.085Ga_0.915N provided evidence for high material quality, even through the epilayer thickness exceeded its critical value. Furthermore, the laser lift-off (LLO) technique is used to fabricate the substrate-free thin-film solar cells (TF-SCs) with a bottom reflector. Although the samples have suffered from thermal-gradient-induced damage during LLO process, the fabricated TF-SCs still exhibit a low forward voltage of 3.3 V at 20 mA along with an ideality factor of 3.1. Finally, since unabsorbed photons can be reflected by the bottom reflector, the TF-SCs show a 13.6% increase in short-circuit current density as compared to their counterparts without a bottom reflector.