M. A. Matin

Prospects of Back Surface Field Effect in Ultra-Thin High-Efficiency CdS/CdTe Solar Cells from Numerical Modeling

Polycrystalline CdTe shows greater promises for the development of cost-effective, efficient, and reliable thin film solar cells. Results of numerical analysis using AMPS-1D simulator in exploring the possibility of ultrathin, high efficiency, and stable CdS/CdTe cells are presented. The conventional baseline case structure of CdS/CdTe cell has been explored with reduced CdTe absorber and CdS window layer thickness, where 1 μm thin CdTe and 50 nm CdS layers showed reasonable efficiencies over 15%. The viability of 1 μm CdTe absorber layer together with possible back surface field (BSF) layers to reduce minority carrier recombination loss at the back contact in ultra thin CdS/CdTe cells was investigated. Higher bandgap material like ZnTe and low bandgap materials like Sb2Te3 and As2Te3 as BSF were inserted to reduce the holes barrier height in the proposed ultra thin CdS/CdTe cells. The proposed structure of SnO2/Zn2SnO4/CdS/CdTe/As2Te3/Cu showed the highest conversion efficiency of 18.6% (Voc = 0.92 V, Jsc = 24.97 mA/cm2, and FF = 0.81). However, other proposed structures such as SnO2/Zn2SnO4/CdS/CdTe/Sb2Te3/Mo and SnO2/Zn2SnO4/CdS/CdTe/ZnTe/Al have also shown better stability at higher operating temperatures with acceptable efficiencies. Moreover, it was found that the cells normalized efficiency linearly decreased with the increased operating temperature with relatively lower gradient, which eventually indicates better stability of the proposed ultra thin CdS/CdTe cells.

Recent Developments of Flexible CdTe Solar Cells on Metallic Substrates: Issues and Prospects

This study investigates the key issues in the fabrication of CdTe solar cells on metallic substrates, their trends, and characteristics as well as effects on solar cell performance. Previous research works are reviewed while the successes, potentials, and problems of such technology are highlighted. Flexible solar cells offer several advantages in terms of production, cost, and application over glass-based types. Of all the metals studied as substrates for CdTe solar cells, molybdenum appears the most favorable candidate, while close spaced sublimation (CSS), electrodeposition (ED), magnetic sputtering (MS), and high vacuum thermal evaporation (HVE) have been found to be most common deposition technologies used for CdTe on metal foils. The advantages of these techniques include large grain size (CSS), ease of constituent control (ED), high material incorporation (MS), and low temperature process (MS, HVE, ED). These invert-structured thin film CdTe solar cells, like their superstrate counterparts, suffer from problems of poor ohmic contact at the back electrode. Thus similar strategies are applied to minimize this problem. Despite the challenges faced by flexible structures, efficiencies of up to 13.8% and 7.8% have been achieved in superstrate and substrate cell, respectively. Based on these analyses, new strategies have been proposed for obtaining cheaper, more efficient, and viable flexible CdTe solar cells of the future.

Design of high efficient and stable ultra-thin CdTe solar cells with ZnTe as a potential BSF

The polycrystalline ultra-thin cadmium telluride (CdTe) is familiar as the potential solar cell material for its higher efficiency, cost-effective, cell stability and clean generation of solar electricity. In this study, a numerical analysis has been performed utilizing AMPS (Analysis of Microelectronic and Photonic Structures) simulator to examine the cell performances (Voc, Jsc, FF and conversion efficiency) of ultra-thin CdTe solar cell. During the research, reduction of CdTe layer was done in the proposed cell and found that 1μm absorber layer is enough for acceptable range for cell conversion efficiency. The possibility of this ultra-thin CdTe absorber layer was examined, as one with 100 nm ZnTe back surface field (BSF) layer to minimize the recombination losses at the back contact and to reduce the barrier height in the valence band of the proposed cell. Higher conversion efficiency of 22.53% (Jsc = 24.28 mA/cm2, FF = 0.875, Voc = 1.06 V) has been achieved with only 0.8 μm of CdTe absorber layer along with 100 nm ZnTe BSF where as conversion efficiency is 18.68% (Jsc = 21.47 mA/cm2, FF = 0.85, Voc = 1.02 V) without BSF layer. Moreover, the proposed CdTe solar cell showed better stability as the normalized efficiency of the proposed cell linearly decreased with the increasing operating temperature at the gradient of -0.16%/°C.

A numerical analysis on CdS:O window layer for higher efficiency CdTe solar cells

Polycrystalline thin film CdTe solar cell continues to be a leading candidate in the PV research and market because of its cost effectiveness and efficiency. In the conventional CdTe cell, polycrystalline cadmium sulfide (CdS) has been used as the best suited n-type heterojunction partner in the last few decades. This study demonstrates the use of novel CdS:O film as n-type heterojunction partner of CdTe cell, which has higher optical band gap (2.42–3.1eV), better lattice-match with CdTe and reduces the unwanted diffused layers than the poly-CdS layer. This novel CdS:O material is utilized in the baseline case of CdTe cell and a cell conversion efficiency as high as 18.5% (Jsc =26.56 mA/cm2, Voc = 0.95 V and FF=0.8) has been found by numerical analysis utilizing AMPS-1D software. The cell normalized efficiency and Voc are found to decrease linearly at the operating temperature gradient of −0.2%/°C, indicating higher stability of the material at higher operating temperatures.

High performance and stable molybdenum telluride PV cells with Indium Telluride BSF

Molybdenum telluride (MoTe₂) is a very promising candidate as PV cell for better cell stability and performance. In this research work, AMPS (Analysis of Microelectronic and Photonic Structures) simulator was used to examine the performance parameters (Jsc, Voc, FF and conversion efficiency) of ultra-thin MoTe₂ PV cell through numerical analysis. During the study, it was found that absorber layer thickness of MoTe₂ PV cell is adequate to achieve cell efficiency at satisfactory level. In addition, the hidden potentiality of MoTe₂ PV cell was examined by inserting Indium Telluride (ImTe₃) back surface field (BSF) between absorber layer and back contact metal. The conversion efficiency of 17.06% (FF = 0.730, V_oc = 0.98 V and J_sc = 23.74 mA/cm²) has been achieved for 1 μm absorber layer of MoTe₂ PV cell without BSF, whereas higher conversion efficiency is 25.29% (FF = 0.847, V_oc = 1.08 V and Jsc = 27.60 mA/cm²) achieved at room temperature with only 0.7 μm of MoTe₂ absorber layer along with 100 nm In₂Te₃ BSF. This research work compares the thermal stability of the structure of MoTe2 PV cell with and without BSF. It was found that the normalized efficiency decreased in response of increasing the operating temperature at the gradient of -0.0275%/°C without BSF. For the addition of In₂Te₃ BSF in the proposed MoTe₂ PV cell, the degradation of normalized efficiency was too less in the range of higher operating temperature.

Design of highly stable and efficient molybdenum telluride PV cells with arsenic telluride BSF

For high efficiency and better thermal stability, Molybdenum Telluride (MoTe<inf>2</inf>) is remarkable as potential photovoltaic (PV) cell. AMPS (Analysis of Microelectronic and Photonic Structures) simulator is used to investigate the cell performance parameters to design the highly efficient ultra-thin MoTe<inf>2</inf> PV cell. In this research work, it has been explored that the cell conversion efficiency of MoTe<inf>2</inf> PV cell is improved with the insertion of Arsenic Telluride (As<inf>2</inf>Te<inf>3</inf>) as back surface field (BSF) above the back contact metal. The highest conversion efficiency of 25.08% was found for As<inf>2</inf>Te<inf>3</inf> BSF with only 0.9 μm of absorber layer whereas it was 17.06% for no BSF with 1 μm thickness of absorber layer. The thermal stability of MoTe<inf>2</inf> PV cell with As<inf>2</inf>Te<inf>3</inf> BSF showed better stability also.

Highly efficient maximum power point tracking using DC–DC coupled inductor single-ended primary inductance converter for photovoltaic power systems

Solar photovoltaics (PVs) have nonlinear voltage–current characteristics, with a distinct maximum power point (MPP) depending on factors such as solar irradiance and operating temperature. To extract maximum power from the PV array at any environmental condition, DC–DC converters are usually used as MPP trackers. This paper presents the performance analysis of a coupled inductor single-ended primary inductance converter for maximum power point tracking (MPPT) in a PV system. A detailed model of the system has been designed and developed in MATLAB/Simulink. The performance evaluation has been conducted on the basis of stability, current ripple reduction and efficiency at different operating conditions. Simulation results show considerable ripple reduction in the input and output currents of the converter. Both the MPPT and converter efficiencies are significantly improved. The obtained simulation results validate the effectiveness and suitability of the converter model in MPPT and show reasonable agreement with the theoretical analysis.

Enhancement the performance of Molybdenum Telluride solar cells with Zinc Telluride BSF

The binary semiconductor compound Molybdenum telluride (MoTe2) is For high efficiency and better thermal stability, Molybdenum telluride (MoTe2) is considered as potential solar cell. AMPS (Analysis of Microelectronic and Photonic Structures) simulator is used to investigate the cell performance parameters for ultra-thin MoTe2 PV cell. In this research work, it has been explored that the cell conversion efficiency of MoTe2 PV cell is improved with the insertion of Zinc Telluride (ZnTe) as back surface field (BSF) above the back contact metal. The highest conversion efficiency of 25.29% was found for ZnTe BSF with only 0.7 µm of absorber layer whereas it was 17.06% for no BSF with 1 µm thickness of absorber layer. The thermal stability of MoTe2 PV cell with ZnTe BSF showed better stability.

Numerical Analysis of Novel Back Surface Field for High Efficiency Ultrathin CdTe Solar Cells

This paper numerically explores the possibility of high efficiency, ultrathin, and stable CdTe cells with different back surface field (BSF) using well accepted simulator AMPS-1D (analysis of microelectronics and photonic structures). A modified structure of CdTe based PV cell SnO2/Zn2SnO4/CdS/CdTe/BSF/BC has been proposed over reference structure SnO2/Zn2SnO4/CdS/CdTe/Cu. Both higher bandgap materials like ZnTe and Cu2Te and low bandgap materials like As2Te3 and Sb2Te3 have been used as BSF to reduce minority carrier recombination loss at the back contact in ultra-thin CdTe cells. In this analysis the highest conversion efficiency of CdTe based PV cell without BSF has been found to be around 17% using CdTe absorber thickness of 5 μm. However, the proposed structures with different BSF have shown acceptable efficiencies with an ultra-thin CdTe absorber of only 0.6 μm. The proposed structure with As2Te3 BSF showed the highest conversion efficiency of 20.8% ( V,  mA/cm2, and ). Moreover, the proposed structures have shown improved stability in most extents, as it was found that the cells have relatively lower negative temperature coefficient. However, the cell with ZnTe BSF has shown better overall stability than other proposed cells with temperature coefficient (TC) of −0.3%/°C.

High efficient and stable ultra-thin CdTe solar cell with a potential Copper Telluride BSF

CdTe is recognized as leading solar cell for having the feature of low cost, high efficiency and better cell stability. The BSF strategy below the absorber layer of CdTe solar cell showed the possibility of higher power conversion efficiency. In this research work, Copper Telluride (Cu2Te) BSF is used to explore the hidden potentiality of CdTe solar cell at ultra-thin level. It was investigated that the addition of Cu2Te BSF significantly enhanced the cell conversion efficiency to 22.51% (Jsc = 24.26 mA/cm2, FF = 0.875, Voc = 1.06 V) with only 0.8 µm of absorber layer in CdTe solar cell. In addition, the cell stability was improved by adding Cu2Te BSF layer in CdTe solar cell and the temperature co-efficient (TC) was 0.16%/°C which indicated better thermal stability.