Design modern structure for heterojunction quantum dot solar cells

Abstract

This paper proposal new structure for improving the optical, electrical characteristics and efficiency of 3rd generation heterojunction quantum dot solar cell (HJQDSC) (ITO/CdS/QDPbS/Au) model by using the quantum dot window layer instead of bulk structure layers cell. Also, this paper presents theoretically analysis for the performance of the proposal HJQDSC (ITO/QDCdS/QDPbS/Au) structure. The new design structure was applied on traditional (SnO2/CdS/CdTe/Cu) and (ZnO/CdS/CIGS/Mo) thin film solar cells which based on sub-micro absorber layer thickness models by replacing the bulk CdTe, CIGS absorber layers and CdS window layer with quantum dot size materials to achieve higher efficiency with lesser usage layer material. Also, it has been studied the effect of using semiconductors layers in quantum dots size on electric and optical properties of thin film solar cells and the effect of window and absorber layers quantum dots radii on the performance of solar cells. Finally, a thermal efficiency analysis has been investigated for explaining the importance of new structure HJQD solar cells.

Ultra-optical characterization of thin film solar cells materials using core/shell absorber layer

“…𝑅 2 radius of the quantum dot semiconductor shell material. 𝜀 𝑠ℎ𝑒𝑙𝑙 is dielectric constant of quantum dot shell semiconductor layer material that described by drude model as shown in [28]- [31] as in (3):…”

“…As shown in (5) the increase in the energy band gap of quantum dot material than the value of bulk material decreases the infinity dielectric constant. The refractive index in quantum dot thin films reduced so it is a great advantage in solar cells application where the reflection also decreased so absorption increases [31]- [34]. The energy band gap 𝐸 𝑔(𝑄𝑑𝑜𝑡𝑠) of quantum dot layer material can be approximated by [30]- [32].…”

“…𝛼 𝑤𝑖𝑄𝐷 is the absorption of quantum dot window layer in core-shell thin film solar cells. 𝛼 𝑏𝑖𝑐𝑠 (𝜆) 𝑎𝑛𝑑 𝛼 𝑤𝑖𝑄𝐷 can be calculated by the Beer-Lambert's law based on refractive index of layers as [31], [35]. Whatever, 𝐽 𝑑𝑖𝑜𝑑𝑖𝑐𝑠 (𝑉) is the forward diode current for heterojunction quantum dot thin film solar cell based on core/shell absorber layer and quantum dot window layer based on [33]- [35] as in (9):…”

“…𝐽 𝑂𝑖𝑐𝑠 is reverse saturation current density in new design for heterojunction quantum dot thin film solar cells based on metallic-semiconductor core/shell absorber layer calculated based on ref. [31], [35]. Where, V is applied voltage.…”

“…The energy band gap of a semiconductor enhances with decreasing refractive index according to various empirical rules and expressions of refractive index and energy band gap. The energy band gap of metallic-semiconductor core/shell absorber layer material 𝐸 𝑔𝑏𝑖 calculated as shown [35], [36]: The total photo generated current density 𝐽 𝑝ℎ𝑖𝑐𝑠 (𝑉) using quantum dot metallic-semiconductor core/shell absorber layer and quantum dot window layer which obtained by integrating over all incident photon wavelengths of the solar spectrum [31], [34], [35].…”