Boosting power conversion efficiencies of quantum-dot-sensitized solar cells beyond 8% by recombination control

Increased Quantum Dot Loading by pH Control Reduces Interfacial Recombination in Quantum-Dot-Sensitized Solar Cells

The power conversion efficiency of quantum-dot-sensitized solar cells (QDSSCs) hinges on interfacial charge transfer. Increasing quantum dot (QD) loading on the TiO2 anode has been proposed as a means to block recombination of electrons in the TiO2 to the hole transport material; however, it is not known whether a corresponding increase in QD-mediated recombination processes might lead to an overall higher rate of recombination. In this work, a 3-fold increase in PbS QD loading was achieved by the addition of an aqueous base to negatively charge the TiO2 surface during Pb cation deposition. Increased QD loading improved QDSSC device efficiencies through both increased light absorption and an overall reduction in recombination. Unexpectedly, we also found increased QD size had the detrimental effect of increasing recombination. Kinetic modeling of the effect of QD size on interfacial charge transfer processes provided qualitative agreement with the observed variation in recombination lifetimes. These results demonstrate a robust method of improving QD loading, identify the specific mechanisms by which increased QD deposition impacts device performance, and provide a framework for future efforts optimizing the device architecture of QDSSCs.

Improved photovoltaic performance and stability of quantum dot sensitized solar cells using Mn-ZnSe shell structure with enhanced light absorption and recombination control

To make quantum-dot-sensitized solar cells (QDSSCs) competitive, photovoltaic parameters comparable to those of other emerging solar cell technologies are necessary. In the present study, ZnSe was used as an alternative to ZnS, one of the most widely used passivation materials in QDSSCs. ZnSe was deposited on a TiO2-CdS-CdSe photoanode to form a core-shell structure, which was more efficient in terms of reducing the electron recombination in QDSSCs. The development of an efficient passivation layer is a requirement for preventing recombination processes in order to attain high-performance and stable QDSSCs. A layer of inorganic Mn-ZnSe was applied to a QD-sensitized photoanode to enhance the adsorption and strongly inhibit interfacial recombination processes in QDSSCs, which greatly improved the power conversion efficiency. Impedance spectroscopy revealed that the combined Mn doping with ZnSe treatment reduces interfacial recombination and increases charge collection efficiency compared with Mn-ZnS, ZnS, and ZnSe. A solar cell based on the CdS-CdSe-Mn-ZnSe photoanode yielded excellent performance with a solar power conversion efficiency of 5.67%, Voc of 0.584 V, and Jsc of 17.59 mA cm(-2). Enhanced electron transport and reduced electron recombination are responsible for the improved Jsc and Voc of the QDSSCs. The effective electron lifetime of the device with Mn-ZnSe was higher than those with Mn-ZnS, ZnSe, and ZnS, leading to more efficient electron-hole separation and slower electron recombination.

Enhanced photovoltaic performance and time varied controllable growth of a CuS nanoplatelet structured thin film and its application as an efficient counter electrode for quantum dot-sensitized solar cells via a cost-effective chemical bath deposition

CuS counter electrodes on FTO substrates are synthesised.

One-step synthesis of solution processed time-dependent highly efficient and stable PbS counter electrodes for quantum dot-sensitized solar cells

A QDSSC with time-dependent optimized PbS CE exhibits a higherηof 4.61% than that of Pt CE (1.34%).

Optimizing the deposition of CdSe colloidal quantum dots on TiO2 film electrode via capping ligand induced self-assembly approach

The influences of experimental parameters in the process of CdSe QD deposition via a capping ligand-induced self-assembly method on the QD loading and the performance of the resultant cell devices have been systematically investigated and optimized.

Graphite powder film-supported Cu2S counter electrodes for quantum dot-sensitized solar cells

A graphite powder (GP) film-supported Cu₂S counter electrode (CE) has been prepared by an accessible and low-temperature method.