Photoelectrochemical (PEC) solar cell properties of chemically deposited cadmium selenide thin films with heteropolyacids

Abstract

The photoelectrochemical (PEC) solar cell properties of chemically deposited cadmium selenide thin films with heteropolyacids have been studied. It has been shown that the PEC solar cell parameters change with the concentration of silicotungstic acid (STA) or phosphotungstic acid (PTA). The best performances are obtained on the electrodes fabricated with 10 −5 M STA or 10 −5 M PTA. Without STA or PTA, the CdSe film in 0.45 M SeSO 3 2− electrolyte showed an open-circuit voltage (V oc) of 510 mV, a short circuit photocurrent density (J sc) of 2.7 mA cm −2, a fill factor of 0.48 and a cell efficiency (η) of 1.6%. The film when grown with 10 −5 M PTA showed the following PEC solar cell parameters: V oc = 570 mV; J sc = 7.6 mA. cm −2, fill factor, 0.55 and η, 5.9%. The CdSe film deposited with 10 −5 M STA showed far superior I-V properties with a V oc of 600 mV, a J sc of 11.8 mA. cm −2, a fill factor of 0.68 and a η of 11.7%. The determination of the chemical composition of the films by X-ray diffraction, XPS and neutron activation analysis have shown the presence of WO 3 in the films deposited with HP As. The improvement of the PEC solar cell properties have been ascribed to the formation of the n-CdSe/n-WO 3 heterojunction which enhances the charge transfer at the semiconductor /electrolyte interface. These results indicated for the first time the interesting effects of STA and PTA on the chemically deposited CdSe films. This opens up a new method to develop mixed electrodes having improved physical properties and PEC solar cells performances.