Whispering Gallery Mode Enabled Efficiency Enhancement: Defect and Size Controlled CdSe Quantum Dot Sensitized Whisperonic Solar Cells

Abstract

A synergetic approach of employing smooth mesoporous TiO2 microsphere (SμS-TiO2)–nanoparticulate TiO2 (np-TiO2) composite photoanode, and size and defect controlled CdSe quantum dots (QD) to achieve high efficiency (η) in a modified Grätzel solar cell, quantum dot sensitized whisperonic solar cells (QDSWSC), is reported. SμS-TiO2 exhibits whispering gallery modes (WGM) and assists in enhancing the light scattering. SμS-TiO2 and np-TiO2 provide conductive path for efficient photocurrent charge transport and sensitizer loading. The sensitizer strongly couples with the WGM and significantly enhances the photon absorption to electron conversion. The efficiency of QDSWSC is shown to strongly depend on the size and defect characteristics of CdSe QD. Detailed structural, optical, microstructural and Raman spectral studies on CdSe QD suggest that surface defects are prominent for size ~2.5 nm, while the QD with size > 4.5 nm are well crystalline with lower surface defects. QDSWSC devices exhibit an increase in η from ≈0.46% to η ≈ 2.74% with increasing CdSe QD size. The reported efficiency (2.74%) is the highest compared to other CdSe based QDSSC made using TiO2 photoanode and I−/I3− liquid electrolyte. The concept of using whispering gallery for enhanced scattering is very promising for sensitized whisperonic solar cells.

Synthesis of CdS/CdSe Core/Shell Heterostructures Using Ultrasonic Assisted Sol–Gel Method

“…With the addition of CdSe to the CdS, the absorption peaks shifted towards the visible region (range 480-520 nm). Results are close agreement with the results [42] and Wang et al [43]. This shift arises due to the defects introduced by lattice mismatch, which occur due to deposition of CdSe over CdS.…”

A Novel Preparation of Nano-Copper Chalcogenide (Cu2S)-based Flexible Counter Electrode

“…Quantum-dot-sensitized solar cells (QDSSCs) use semiconductor quantum dots (QDs) in sensitizers, instead of organic dyes. As a result, QDSSCs exhibit the unique advantages of quantum size effect, multi-exciton effect, large absorption coefficient, and easy matching of energy levels between the electron donor and acceptor materials 3,4 . The structure of a QDSSC is sandwich-like and mainly consists of a photoanode, electrolyte, and counter electrode.…”

In Situ Microwave‐Assisted Fabrication of Hierarchically Arranged Metal Sulfide Counter Electrodes to Boost Stability and Efficiency of Quantum Dot‐Sensitized Solar Cells

“…Additionally, low cost and convenient fabrication of QDSSCs photovoltaic devices are of paramount importance in overcoming the hurdle of commercially lucrative cells' production. Over the years, several semiconductor QDs, such as CdS, CdSe, PbS, and CuInS 2 , have been introduced, and significant progress in achieving higher power conversion efficiency (PCE) has been made. However, the champion PCE of 12.75% is still far behind the maximum thermodynamic conversion efficiency of 44% …”