Effect of the shell material and confinement type on the conversion efficiency of core/shell quantum dot nanocrystal solar cells

Abstract

In this study, the effects of the shell material and confinement type on the conversion efficiency of core/shell quantum dot nanocrystal (QDNC) solar cells have been investigated in detail. For this purpose, the conventional, i.e. original, detailed balance model, developed by Shockley and Queisser to calculate an upper limit for the conversion efficiency of silicon p-n junction solar cells, is modified in a simple and effective way to calculate the conversion efficiency of core/shell QDNC solar cells. Since the existing model relies on the gap energy ([Formula: see text]) of the solar cell, it does not make an estimation about the effect of QDNC materials on the efficiency of the solar cells, and gives the same efficiency values for several QDNC solar cells with the same [Formula: see text]. The proposed modification, however, estimates a conversion efficiency in relation to the material properties and also the confinement type of the QDNCs. The results of the modified model show that, in contrast to the original one, the conversion efficiencies of different QDNC solar cells, even if they have the same [Formula: see text], become different depending upon the confinement type and shell material of the core/shell QDNCs, and this is crucial in the design and fabrication of the new generation solar cells to predict the confinement type and also appropriate QDNC materials for better efficiency.

Comparative Analysis of Excitonic and Biexcitonic Effects on the Power Conversion Efficiency of a CdSe/CdTe/ZnTe Quantum Dot Solar Cell

“…The QY is equivalent to the external quantum efficiency (EQE), which measures the collection probability of the excited carriers ($$C(h\nu)$$), the reflectivity of the solar cell ($$R(h\nu)$$), and the absorptivity of the solar cell ($$a(h\nu)$$). This relationship can be expressed as [39] $$$$\begin{equation} \mathrm{EQE}(h\nu)=C(h\nu)(1-R(h\nu))a(h\nu) \end{equation}$$$$…”

“…The value of $$V$$ is the voltage that maximizes the PCE of the solar cell and is determined through numerical search. Since emission is a component of the recombination current density, the emissivity, $$\epsilon (h\nu)$$, is replaced by the absorptivity in the $$\mathrm{EQE}(h\nu)$$ formula as follows [ 39 ] $$$$\begin{equation} \mathrm{EQE}(h\nu)=C(h\nu)(1-R(h\nu)) \epsilon (h\nu) \end{equation}$$$$…”

“…This is achieved by incorporating the oscillator strength parameter into the collection probability, that is, $$C(h\nu) = f \mathrm{QY}(h\nu)$$. In MDBM, with this integration the recombination current density can be expressed as follows [ 39 ] : $$$$\begin{equation} J_{rc}=\frac{2\pi q_e}{h^3 c^2} \int _{E_g}^{\infty } \frac{f \mathrm{QY}(h\nu,E_g)(h\nu)^2}{e^{(h\nu -f q_e V \mathrm{QY}(h\nu,E_g))/kT}-1} \,d(h\nu) \end{equation}$$$$…”

“…This model serves as a foundational tool in the field, providing a methodology for calculating the maximum PCE based on the bandgap energy of the semiconductor material utilized in the solar cell. Conversely, Sahin [ 39 ] has enhanced the detailed balance model by incorporating oscillator strength, a parameter reflecting the distinct confinement regimes, recombination mechanisms, and lifetimes of QD structures, into the calculation of recombination current density. Accordingly, the MDBM can provide a PCE value specific to each structure employed in the solar cell.…”

Ag-Doped ZnInS/ZnS Core/Shell Quantum Dots for Display Applications

“…Hence, it improves the emissive properties of the QDs with longer Photoluminescence (PL) lifetimes and enhanced chemical stabilities and has the benefit of suppressing self-absorption. − In addition, precise shelling also reduces Auger recombination and the blinking effect . Among the alternative toxic counterparts, wider band-gap zinc chalcogenides (ZnS and ZnSe) − have been been put forward as promising shells material owing to their good optical characteristics and stability. Zhang et al reported an enhanced PL lifetime (from 0.13 to 3.50 μs) and high photochemical and thermal stabilities of Cu,Mn:Zn–In–S/Zn–S-codoped QDs due to thick shell growth …”