Efficiency enhancement using a Zn_{1− x}Ge_x-O thin film as an n-type window layer in Cu₂O-based heterojunction solar cells

Abstract

Efficiency enhancement was achieved in Cu2O-based heterojunction solar cells fabricated with a zinc–germanium-oxide (Zn1− x Ge x -O) thin film as the n-type window layer and a p-type Na-doped Cu2O (Cu2O:Na) sheet prepared by thermally oxidizing Cu sheets. The Ge content (x) dependence of the obtained photovoltaic properties of the heterojunction solar cells is mainly explained by the conduction band discontinuity that results from the electron affinity difference between Zn1− x Ge x -O and Cu2O:Na. The optimal value of x in Zn1− x Ge x -O thin films prepared by pulsed laser deposition was observed to be 0.62. An efficiency of 8.1% was obtained in a MgF2/Al-doped ZnO/Zn0.38Ge0.62-O/Cu2O:Na heterojunction solar cell.

Optical Analysis of a ZnO/Cu<sub>2</sub>O Subcell in a Silicon-Based Tandem Heterojunction Solar Cell

“…The theoretical limit of the conversion efficiency for a solar cell based on Cu 2 O is approximately 20% under one sun illumination [11]. However, the highest conversion efficiency achieved experimentally is 8.1% for a ZnO/Cu 2 O solar cell based on thermally oxidized copper sheets [12], suggesting that further investigation of Cu 2 O-based solar cells is still needed in order to realize their full potential in photovoltaic applications.…”

Tandem Solar Cells Based on Cu2O and c-Si Subcells in Parallel Configuration: Numerical Simulation

“…The theoretical limit of the power conversion efficiency for a Cu 2 O solar cell is approximately 20% [13,14] under the solar radiation spectrum AM 1.5G. However, the highest conversion efficiency of 81% achieved experimentally for a solar cell made up of zinc oxide (ZnO) and Cu 2 O based on thermally oxidized copper sheets [15] suggests the potential of further increase of the conversion efficiency.…”

“…For the Cu 2 O subcell, a wide range of possible n-type materials, including ZnO, ZnS, TiO 2 , CdS, and Ga 2 O 3 [13][14][15] can be used. There are two possibilities of electrical connection for the two subcells, namely, series and parallel.…”

Stability Improvement of Photovoltaic Performance in Antimony Sulfide-Based Hybrid Solar Cells

“…4 Although Sb 2 S 3 -based solar cell seems to be stable in air, 1,14 stability test under the accelerated conditions has not yet been reported. In addition, various materials such as TiO 2 , 1 ZnO, [15][16][17][18] or SnO 2 19 have been utilized as an electron transporting layer (ETL) and polythiophenes, 1-4 2,2',7,7'-tetrakis(N,Ndi-p-methoxyphenylamine)-9,9'-spirobifluorene, 20 ZnPc, CuSCN, …”

“…4 Although Sb 2 S 3 -based solar cell seems to be stable in air, 1,14 stability test under the accelerated conditions has not yet been reported. In addition, various materials such as TiO 2 , 1 ZnO, [15][16][17][18] or SnO 2 19 have been utilized as an electron transporting layer (ETL) and polythiophenes, 1-4 2,2',7,7'-tetrakis(N,Ndi-p-methoxyphenylamine)-9,9'-spirobifluorene, 20 ZnPc, CuSCN, 21 MoO 3 , 22 or NiO 23 have been used as a hole transporting layer (HTL) of the Sb 2 S 3 based solar cells, however, optimization of the combinations of ETL and HTL in terms of the durability has also not yet been explored. In this context, we prepared Sb 2 S 3 -based solar cells with TiO 2 or ZnO nanoparticles for ETL in addition to poly(3-hexylthiophene)-2,5-diyl (P3HT)/ (3, 4-ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT: PSS), ZnPc, or MoO 3 for HTL and compared their photovoltaic properties with encapsulation by using glass and UV cutoff films under JIS C8938 conditions of 1 sun at 63…”