A simple strategy for improving the energy conversion of multilayered CdTe quantum dot-sensitized solar cells

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Abstract
In this paper we describe the preparation of CdTe quantum dot-sensitized solar cells (QDSSCs). We coated FTO substrates with 21 nm-diameter TiO2nanoparticles (NPs) and then immersed the system in poly(dimethyldiallylammonium chloride) (PDDA) solution under ambient conditions. The treated substrates were then subjected to 3 nm-diameter CdTe NP solution at 100 °C for various periods of times. To increase the degree of deposition and to obtain CdTe QDs of various sizes, we performed the coating of the CdTe QDs through three heating cycles for 24, 12, or 6 h. The as-prepared (TiO2)3-PDDA-(QDCdTe)3-FTO electrodes were then used to fabricate (TiO2)3-PDDA-(QDCdTe)3-FTO QDSSCs employing 1-ethyl-3-methylimidazolium thiocyanate incorporating 1.0 M LiI and 0.1 M I2 as electrolytes. The heating treatment allows the QDSSCs to harvest energy at a higher efficiency in the visible region of solar light. As a result, the as-prepared QDSSCs feature a high energy conversion efficiency (η = 2.02%) and a high open-circuit photovoltage (Voc = 850 mV) at 100% sunlight (AM1.5, 100 mW/cm2).