Influence of Mn+2 incorporation in CdSe quantum dots for high performance of CdS–CdSe quantum dot sensitized solar cells

Abstract

Quantum dot sensitized solar cells (QDSSCs) have attracted considerable attention recently and become promising candidates for realizing a cost-effective and facile fabrication of solar cell with improved photovoltaic performance. QDs were directly grown on the TiO2 mesostructure by the successive ionic layer absorption and reaction (SILAR) technique. QDSSC based on CdS–CdSe photoanode achieves a power conversion efficiency of 3.42% under AM 1.5 G one sun illumination. The loading of Mn+2 metal ions was applied to a CdSe (CdS–Mn–CdSe) photoanode to enhance the absorption in QDSSCs, which greatly improved the power conversion efficiency. Without the passivation layer, the solar cell based on a CdS–Mn–CdSe QD-sensitized TiO2 photoelectrode shows higher Jsc (14.67 mA/cm2), Voc (0.590 V) and power conversion efficiency (4.42%) comparing to Mn-undoped CdS–CdSe QD sensitized TiO2 (Jsc: 11.29 mA/cm2, Voc: 0.568 V, and efficiency: 3.42%), which can be ascribed to superior light absorption, faster electron transport and slower charge recombination for the former. The effective electron lifetime of the device with CdS–Mn–CdSe was higher than those with CdS–CdSe, leading to more efficient electron–hole separation and slower electron recombination. The effects of Mn+2 metal ions on the chemical, physical, and photovoltaic properties of the QDSSCs have been investigated have been investigated by X-ray photon spectroscopy (XPS), UV–vis spectra, photocurrent–voltage (J–V) characteristics and electrochemical impedance spectra (EIS).