High performance PbS quantum dot sensitized solar cells via electric field assisted in situ chemical deposition on modulated TiO2 nanotube arrays

Abstract

Quantum dot sensitized solar cells (QDSSCs) are attractive photovoltaic devices due to their simplicity and low material requirements. However, efforts to realize high efficiencies in QDSSCs have often been offset by complicated processes and expensive or toxic materials, significantly limiting their useful application. In this work, we have realized for the first time, high performance PbS QDSSCs based on TiO₂ nanotube arrays (NTAs) via an in situ chemical deposition method controlled by a low electric field. An efficiency, η, of ∼3.41% under full sun illumination has been achieved, which is 133.6% higher than the best result previously reported for a simple system without doping or co-sensitizing, and comparable to systems with additional chemicals. Furthermore, a high open-circuit voltage (0.64 V), short-circuit current (8.48 mA cm⁻²) and fill factor (0.63) have been achieved. A great increase in the quantity of the loaded quantum dots (QDs) in the NTAs was obtained from the in situ electric field assisted chemical bath deposition (EACBD) process, which was the most significant contributing factor with respect to the high J_SC. The high V_OC and FF have been attributed to a much shorter electron path, less structural and electronic defects, and lower recombination in the ordered TiO₂ NTAs produced by oscillating anodic voltage. Besides, the optimal film thickness (∼4 μm) based on the NTAs was much thinner than that of the control cell based on nanoporous film (∼30.0 μm). This investigation can hopefully offer an effective way of realizing high performance QDSSCs and QD growth/installation in other nanostructures as well.