Substrate-free large gap InGaN solar cells with bottom reflector

In this study, we report on the realization of the In0.085Ga0.915N 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-In0.085Ga0.915N epilayer. The sharp and narrow signals in the photoluminescence spectra of In0.085Ga0.915N 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.