Progress toward 20% efficiency in Cu(In,Ga)Se2 polycrystalline thin-film solar cells

Mendelsberg

Applied Surface Science

et al. 2013

Title AbstractIndium doped cadmium oxide (CdO:In) films with different In concentrations were prepared on low-cost glass substrates by pulsed filtered cathodic arc deposition (PFCAD). It is shown that polycrystalline CdO:In films with smooth surface and dense structure are obtained. In-doping introduces extra electrons leading to remarkable improvements of electron mobility and conductivity, as well as improvement in the optical transmittance due to the Burstein-Moss effect. CdO:In films on glass substrates with thickness near 230 nm show low resistivity of 7.23×10 -5 Ωcm, high electron mobility of 142 cm 2 /Vs, and mean transmittance over 80% from 500-1250 nm (including the glass substrate). These high quality pulsed arc-grown CdO:In films are potentially suitable for high efficiency multi-junction solar cells that harvest a broad range of the solar spectrum. Keywords:In doped cadmium oxide; pulsed filtered cathodic arc deposition; transparent conductors IntroductionTransparent conducting oxides (TCOs) have attracted much attention due to their tremendous importance in optical and electrical applications such as displays, touch-screens, thin film solar cell technology and for transparent conducting electrodes in general [1,2]. For solar cell applications, high mobility TCO contacts with a sheet resistance of <10 Ω/□ and an optical transmission >80% over the visible to near infrared wavelengths (bandgap >3 eV) can enhance the efficiency [3]. This is particularly effective for multi-junction solar cells which consist of different semiconductor stacks with appropriately matched bandgaps that are tuned to increase the spectral response over the entire solar spectrum [4]. Therefore, in addition to maintaining high conductivity, improving the visible to near infrared transparency of TCO films is of great importance for applications in high performance multi-junction solar cells.

Section: Introductionmentioning

confidence: 99%

Transparent and conductive indium doped cadmium oxide thin films prepared by pulsed filtered cathodic arc deposition

Mendelsberg

Applied Surface Science

et al. 2013

Journal of the Optical Society of Korea

“…Recently, the Cu(In,Ga)Se2 (CIGS) thin-film solar cell has been the subject of intensive research and development in the photovoltaic industry [1][2][3][4][5][6]. CIGS has a great potential for solar cells with high power-conversion efficiencies.…”

Section: Introductionmentioning

confidence: 99%

“…CIGS has a great potential for solar cells with high power-conversion efficiencies. The record efficiency for a small-size CIGS thin-film solar cell is about 20 % [1]. CIGS solar cells can also be fabricated on a wide-area substrate cost-effectively [3][4].…”

Section: Introductionmentioning

confidence: 99%

Analysis of the Current-voltage Curves of a Cu(In,Ga)Se₂ Thin-film Solar Cell Measured at Different Irradiation Conditions

Lee¹,

Chung²,

Park³

et al. 2010

We analyze the current density -voltage (J -V) curve of a Cu(In,Ga)Se2 (CIGS) thin-film solar cell measured at different irradiation power densities. For the solar-cell sample investigated in this study, the fill factor and power conversion efficiency decreased as the irradiation power density (IPD) increased in the range of 2 to 5 sun. Characteristic parameters of solar cell including the series resistance (rs), the shunt resistance (rsh), the photocurrent density (JL), the saturation current density (Js) of an ideal diode, and the coefficient (Cs) of the diode current due to electron-hole recombination via ionized traps at the p-n interface are determined from a theoretical fit to the experimental data of the J -V curve using a two-diode model. As IPD increased, both rs and rsh decreased, but Cs increased.

Journal of Applied Physics

“…Solar cells made from the quaternary alloy Cu͑In, Ga͒Se 2 have achieved efficiencies Ͼ 19%, 1 i.e., more than any other thin film approach despite the polycrystallinity of the material. One commonly used characterization tool for photovoltaic absorber materials is the analysis of the photoluminescence, e.g., for the study of defect related properties.…”

Section: Introductionmentioning

confidence: 99%

Electroluminescence analysis of high efficiency Cu(In,Ga)Se2 solar cells

Kirchartz

Rau

2007

We compare the electroluminescence (EL) of polycrystalline ZnO∕CdS∕Cu(In,Ga)Se2 heterojunction solar cells with similar band gaps but different open circuit voltages, indicating a difference in the electronic quality of the absorber. Temperature dependent EL measurements reveal that all cells feature transitions from donor-acceptor pair recombination at lower temperature to band to band recombination at higher temperatures. However, the less efficient cells show a longer transition range with donor-acceptor pair recombination still apparent at room temperature. We find further that the part of the room temperature spectrum that is due to band to band transitions in the respective cells is relatively broader than expected from a direct semiconductor with a homogeneous band gap. We analyze this spectral broadening by a model that accounts for band gap fluctuations of the absorber material. The experimental results show that the dominant part of this spectral broadening results from the intentional band gap grading and not from stochastic band gap fluctuations. We show further that the spectral EL emission is linked to the photovoltaic external quantum efficiency by electro-optical reciprocity. In a similar way, the external EL quantum efficiency is related to the open circuit voltage of the device. We verify experimentally that the difference between radiative and measured open circuit voltage determines the EL external quantum efficiency of the solar cell. The best Cu(In,Ga)Se2 solar cell reaches an external light emitting diode quantum efficiency of around 0.1%.