Defect states in hybrid solar cells consisting of Sb2S3 quantum dots and TiO2 nanoparticles

Abstract

We have studied defect states in an organic-inorganic hybrid solar cell containing Sb2S3 quantum dots (QDs) and TiO2 nanoparticles (NPs) by using deep level transient spectroscopy (DLTS). An Au electrode was deposited as a Schottky contact on the sample, where the Sb2S3 QDs were distributed on the surface of TiO2 NPs by chemical synthesis. The activation energy and capture-cross section of an interface state between the Sb2S3 QDs and the TiO2 NPs were found to be about 0.78 eV and 2.21 × 10−9 cm−2, respectively. Also, the densities of this interface trap under a measurement voltage of −1 V were approximately 2.5 × 1017 cm−3. Based on these results, the interface trap was positioned around Ec − 1.03 eV below the conduction band edge of Sb2S3 QD. Thus, the external quantum efficiency of the solar cell was affected because of its role as a recombination center for carriers generated from Sb2S3 QDs.

Spin-coated planar Sb2S3 hybrid solar cells approaching 5% efficiency

“…The typical crystallization temperature is 300 °C [2,6,29,31,37] while values of 330 °C [4–5 32,50] and up to 400 °C [51] are reported. To gain insights into the crystallization behavior in terms of morphology, creation of defects and solar cell performance we produced samples crystallized on a hot plate at various temperatures in a nitrogen atmosphere.…”

Sb2S3 grown by ultrasonic spray pyrolysis and its application in a hybrid solar cell

“…An absorber bandgap of 1.65 eV is found in solar cells with Sb 2 S 3 prepared by ALD [5,19] or in solar cells with Sb 2 S 3 prepared by CBD, as estimated from the photocurrent edge at around 750 nm in the published EQE plots [2,4,6–9 11–12 15–17 40–41 50–53]. Any E g larger than 1.7 eV up to 2.6 eV have been attributed to nanocrystalline Sb 2 S 3 [1,44,54], or to amorphous Sb 2 S 3 [6,44–45 53], while it is also known that contamination, most notably with oxygen, can significantly increase the bandgap value of metal sulfide films [23,55–56]. Values of 1.52–1.55 eV are reported for layers of nanotubes, -rods, or -flakes that consist of single phase Sb 2 S 3 [57–59].…”

“…The present paper relies on the recently proven concept of TiO 2 /Sb 2 S 3 /P3HT solar cells [1–12], in which Sb 2 S 3 is the light absorber, also called the sensitizer, situated in the electrical junction created by TiO 2 and P3HT (polythiophene) as the electron and hole conductor, respectively. For these type of solar cells, fluorine doped tin oxide (FTO) is prevalently used to contact the TiO 2 while evaporated Au has been used to contact the P3HT.…”

Sb2S3 Solar Cells

“…Because of the large surface area in SSCs, the performance will be limited primarily by interface defects, which in some studies was found to be on the order of 10 11 -10 12 cm À2 at the TiO 2 -mp/Sb 2 S 3 -nc interface. 110 On the other hand, Darga et al argued that dominant recombination events in TiO 2 /Sb 2 S 3 with flat geometry stems from the bulk Sb 2 S 3 . 93 Additionally, according to the temperature-dependent electrical conductivity measurements of thin Sb 2 S 3 films, the determined activation energy was in the 0.5-0.9 eV range, 67,111,112 the Fermi level was found to be pinned at near midgap, 67 and high activation energy was calculated by DLTS, 90 all strongly suggesting the existence of deep traps.…”