n-ZnSe/p-GaAs heterojunction solar cells

For PV applications, epitaxial layers of n-ZnSe were grown by metal-organic vapour phase epitaxy (MOVPE) at 340°C on GaAs(001) substrates. n-type net carrier concentration in the range between 10¹⁷-10¹⁹ cm^-3 was demonstrated. By increasing the doping concentration, the double crystal X-ray diffraction full width at half maximum of 1.2 μm thick ZnSe-layers increased from 400" to 600". A first n-ZnSe/p-GaAs solar cell achieved an open circuit voltage of 706 mV, a fill factor of 65% and a short circuit current density of 10 mA cm^-2 (total area, ELH-lamp, 100 mW cm^-2, no AR-coating). J_SC was increased by 4 mA cm^-2 by depositing sputtered n⁺-ZnO on the n-ZnSe layer. In order to improve the PV performance further, n-ZnSe will be grown on GaAs buffer layers, the doping profile will be optimised systematically and MgF₂ will be deposited on the ZnO layer