Solar Energy Conversion at the p ‐ InP / Vanadium3 + / 2 + Semiconductor/Electrolyte Contact: A Study Based on Differential Capacitance and Current‐Voltage Data

Abstract

Previously unachieved values are obtained for the open‐circuit voltage (0.7 to 0.8 V) and the fill‐factor (76%) at the illuminated semiconductor/electrolyte contact (‘100’ face) coated with a submonolayer amount of silver. Photoelectrochemical solar cell efficiency is 11%, despite significant optical reflection and electrolyte absorption losses. Differential capacitance measurements demonstrate a semiconductor/surface energy barrier height of up to , independent of the Ag treatment. This value is considerably larger than typically found at solid‐state contacts. Barrier heights derived from Mott‐Schottky data are compared to photovoltages; results indicate that interface recombination and a slow charge‐transfer (bare ) and thermionic emission from the metal (Ag‐treated ) are important factors limiting the cell efficiency. Flatband potential shifts owing to a slow charge‐transfer under photocurrent flow are reduced by the Ag treatment. In a finite potential range of about 400 mV (0 to −400 mV/SCE), both photovoltages and Mott‐Schottky data reveal an unpinned Fermi level at bare and Ag‐treated electrodes. The unpinned barrier follows the ideal Schottky barrier model for an absolute SCE potential of −5.0 eV/SCE. Reference to related work at and is made.