Enhanced conversion efficiency of InGaN multiple quantum well solar cells grown on a patterned sapphire substrate

Lee, Ya Ju; Lee, Min-Hung; Cheng, Chin-Pao; Yang, Chia Hao

doi:10.1063/1.3605244

Cited by 36 publications

(18 citation statements)

References 20 publications

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“…The shunt resistance exhibits nearly a linear decreasing relationship with Mg-doping concentration. It is known that R sh is mainly caused by short circuit pathways, such as threading dislocations (TDs) [17] , thus the linear relationship agrees well with the XRD and dark J-V measurement results. On the other hand, slight doping (5×10 17 cm -3 ) almost reduces the shunt resistance by half from sample A to sample B, but the effect becomes inconspicuous when the doping concentration is further increased.…”

supporting

confidence: 77%

Effects of Mg-doping concentration on the characteristics of InGaN based solar cells

Wang

2015

Optoelectron. Lett.

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A major challenge in GaN based solar cell design is the lack of holes compared with electrons in the multiple quantum wells (MQWs). We find that GaN based MQW photovoltaic devices with five different Mg-doping concentrations of 0 cm -3 , 5×10 17 cm -3 , 2×10 18 cm -3 , 4×10 18 cm -3 and 7×10 18 cm -3 in GaN barriers can lead to different hole concentrations in quantum wells (QWs). However, when the Mg-doping concentration is over 1×10 18 cm -3 , the crystal quality degrades, which results in the reduction of the external quantum efficiency (EQE), short circuit current density and open circuit voltage. As a result, the sample with a slight Mg-doping concentration of 5×10 17 cm -3 exhibits the highest conversion efficiency.Nowadays, InGaN ternary alloys have drawn great attention in the field of optoelectronics due to their unique physical characteristics, including excellent radiation resistance, good thermal conductivity, large absorption coefficients (~10 5 cm -1 ) [1] and wide band gap (varying from 0.64 eV to 3.4 eV) covering most of the solar spectrum [2][3][4][5][6][7] , which makes them suitable for producing solar cells.Until now, there are several difficulties in the fabrication of InGaN based solar cells with high efficiency. Firstly, the hole mobility in the InGaN material is about 10 cm 2 /(V·s), but the electron mobility in the InGaN material is about 100 cm 2 /(V·s), so there is relatively large lack of holes in InGaN based optoelectronic devices. Secondly, InGaN layers with higher indium (In) proportion are needed to fabricate InGaN-based multijunction solar cells with nearly ideal band gaps for maximum solar energy conversion efficiency. The earlier theoretical calculation indicated that an active material system with power conversion efficiency greater than 50% could be achieved by InGaN alloys with In proportion of about 40% [5] . Unfortunately, the fabrication of solar cells with large In proportion remains a challenge, because of the large lattice mismatch between indium nitride and gallium nitride. When the layer thickness and/or In proportion of InGaN alloys increase, In clusters in InGaN films easily lead to phase separation, which results in the lower open circuit voltages (V oc ) compared with theoretical values, the low fill factors (FFs) and degradation of the short-circuit current density (J sc ) [6][7][8][9][10] .To partially overcome the In incorporation limitation in thick layers, many researchers have adopted multiple quantum wells (MQWs) or superlattice absorbing layers [11][12][13] . InGaN based MQW optical devices can not only obtain higher crystal quality of InGaN absorption layers embedded between GaN barriers, but also optimize V oc and J sc independently by adjusting parameters of quantum barrier and well materials [14] . However, up to now, the energy harvesting efficiency of these devices is not comparable to the theoretical value of devices with a corresponding In mole fraction. To improve the performance of InGaN-based photovoltaic device, it is urgent to implement the in...

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supporting

confidence: 77%

Effects of Mg-doping concentration on the characteristics of InGaN based solar cells

Wang

2015

Optoelectron. Lett.

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“…A better crystal quality means less defects, and this is good for the solar cell. The leakage current is caused by short circuit paths, such as the defects [8] . If the cell has less defects, it would have a large shunt resistance and a low leakage current, contributing to a high conversion efficiency.…”

Section: Experimental Methodsmentioning

confidence: 99%

“…For the solar cell, its equivalent circuit consists of a constant flow source, a parallel diode, a series resistance (R s ) and shunt resistance (R sh ), as shown in the figure 1(b). Shunt resistance is caused by the leakage current and series resistance is decided by the excessive contact resistance or the resistance of neutral region [8] . The external quantum efficiency (EQE) measurement was tested under monochromatic illumination by a tungsten halogen light source and the intensity of the incident light is calibrated by a reference silicon photodetector.…”

Section: Experimental Methodsmentioning

confidence: 99%

The study of optical properties of InGaN-based solar cell with blue emission wavelength

et al. 2015

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The III-N material system (including alloys of InN, AlN, and GaN) has several characteristics which give it key advantages over the existing solar cell materials, for example, the high absorption coefficient and high carrier mobility, more important, the wide range of band gap energies which spans nearly the entire solar spectrum. In this paper, we fabricated a multiple quantum well (MQW) InGaN/GaN solar cell. The photovoltaic characteristics of the device was demonstrated that, the short circuit current density (J SC ) is about 0.43mA/cm 2 , the open circuit voltage is about 2.2 eV, and the fill factor is about 81%. But the peak external quantum efficiency (EQE) is not very high, only 30%. And the conversion efficiency is about 0.83%, so more work for device design should be done in the future.

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“…It is clear that the performance of the devices on PSS is better than the other one on the planar substrate. The reason is that the film grown on PSS exhibit better crystal qualities and optical qualities, which will be beneficial to enhancing light absorption and increasing the photon-generated carriers [11]. At the same time, it is also helpful to extending the light path length in the device and absorbing more photons.…”

Section: Methodsmentioning

confidence: 99%

“…It has been reported in others' works that there are a large number of stacking faults appeared during the initial growth of GaN buffer layer. These stacking faults interact with the threading dislocation (TD) defects, preventing further penetration into the MQWs [11]. Figure 3 shows the comparison of J-V characters of these two samples.…”

Section: Methodsmentioning

confidence: 99%

In GaN Multiple Quantum Well Solar Cells on a Patterned Sapphire Substrate

Bi¹,

Zhang²,

Hao³

2015

Proceedings of the AASRI International Conference on Industrial Electronics and Applications (2015)

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Enhanced conversion efficiency of InGaN multiple quantum well solar cells grown on a patterned sapphire substrate

Cited by 36 publications

References 20 publications

Effects of Mg-doping concentration on the characteristics of InGaN based solar cells

Effects of Mg-doping concentration on the characteristics of InGaN based solar cells

The study of optical properties of InGaN-based solar cell with blue emission wavelength

In GaN Multiple Quantum Well Solar Cells on a Patterned Sapphire Substrate

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