Life cycle assessment of thin‐film GaAs and GaInP/GaAs solar modules

This paper presents an environmental comparison based on life cycle assessment (LCA) of the production under average European circumstances and use in The Netherlands of modules based on two kinds of III–V solar cells in an early development stage: a thin‐film gallium arsenide (GaAs) cell and a thin‐film gallium‐indium phosphide/gallium arsenide (GaInP/GaAs) tandem cell. A more general comparison of these modules with the common multicrystalline silicon (multi‐Si) module is also included. The evaluation of the both III–V systems is made for a limited industrial production scale of 0·1 MW_p per year, compared to a scale of about 10 MW_p per year for the multi‐Si system. The here considered III–V cells allow for reuse of the GaAs wafers that are required for their production. The LCA indicates that the overall environmental impact of the production of the III–V modules is larger than the impact of the common multi‐Si module production; per category their scores have the same order of magnitude. For the III–V systems the metal‐organic vapour phase epitaxy (MOVPE) process is the main contributor to the primary energy consumption. The energy payback times of the thin‐film GaAs and GaInP/GaAs modules are 5·0 and 4·6 years, respectively. For the multi‐Si module an energy payback time of 4·2 years is found. The results for the III–V modules have an uncertainty up to approximately 40%. The highly comparable results for the III–V systems and the multi‐Si system indicate that from an environmental point of view there is a case for further development of both III–V systems. Copyright © 2006 John Wiley & Sons, Ltd.     

多结太阳电池辐射损伤的电致发光研究

建立了电致发光测试方法,对一种国产GaInP/GaAs/Ge三结太阳电池1MeV电子辐照后各子电池的辐照特性进行了研究,并与光谱响应结果进行了比较。讨论了GaInP/GaAs/Ge三结太阳电池的辐射损伤机理。     

HBT电压控制振荡器的相位噪声

研究了电压控制振荡器（ＶＣＯ）的相位噪声与构成该振荡器的有源器件的低频噪声的关系,测试了ＳｉＢＪＴ、ＡｌＧａＡｓ／ＧａＡｓ ＨＢＴ和ＧａＩｎＰ／ＧａＡｓ ＨＢＴ的低频噪声,并分析了各自低频噪声产生的原因,提出了选择ＧａＩｎＰ／ＧａＡｓ ＨＢＴ ＶＣＯ来实现微波固体振荡器低相位噪声化这一发展方向。     

Luminescence coupling effects on multijunction solar cell external quantum efficiency measurement

The effects of luminescence coupling on the external quantum efficiency (EQE) measurement of an InGaP/InGaAs/Ge triple junction solar cell were investigated. A small signal model was used to study the interaction of the subcells during EQE measurement. It was found that an optical–electrical feedback mechanism results in EQE measurement artifacts. Measurements of luminescence from the InGaP p–n junction are also performed to quantitatively determine the strength of the luminescence coupling. These results offer a more thorough and comprehensive interpretation of EQE measurement results that are needed for the design and accurate performance evaluation of high‐efficiency multijunction solar cells. The effects demonstrated here can also be used to measure the spontaneous emission efficiency of the subcells, which is useful for nondestructive assessment of multijunction solar cell material quality. Copyright © 2011 John Wiley & Sons, Ltd.     

QE测量在GaInP/GaAs叠层电池研究中的应用

该文介绍量子效率测量(QE测量)的原理以及此项技术在太阳电池研究中的应用.重点介绍QE测量在GaInP/GaAs叠层电池研究中的应用.给出了作者在美国Toledo大学进行的GaInP/GaAs叠层电池的QE测量的部分结果,并把这些结果与非晶硅(a-Si)三结叠层电池的QE测量结果进行了比较,对GaInP/GaAs叠层电池研究中的问题进行了分析,提出了改进的意见.     

Influence of GaInP ordering on the performance of GaInP solar cells

CuPt-type ordering with undesirable properties always occurs in GaInP at growth conditions that are very close to those leading to the highest quality material in metal organic chemical vapor deposition. In this work, highly disordered GaInP with high crystalline quality was obtained by optimizing growth conditions. Room-temperature and low-temperature photoluminescence (PL) spectra of AlGaInP/GaInP/AlGaInP double heterostructures (DHs) reveal that the band edge emission intensity is enhanced by optimizing growth temperature, V/III ratio, and reactor pressure at the expense of low energy peak originating from spatially indirect recombination due to the ordering-related defects. The DH sample with less ordering-related defects demonstrates a longer effective minority carrier lifetime, consequently, the GaInP solar cell shows a significant improvement in the performance.     

Adjusted NIEL calculations for estimating proton-induced degradation of GaInP/GaAs/Ge space solar cells

The non-ionizing energy loss (NIEL) values for protons in solar cells should be modified by taking into account the distribution of the Bragg damage peak in the active region to calculate the corresponding displacement damage dose. In this paper, based upon a thin target approximation, a new approach is presented to modify NIEL values for protons on a GaAs sub-cell. Adjusted NIEL values can be used to estimate the degradation induced by protons on GaInP/GaAs/Ge triple-junction space solar cells.     

Stretchable semiconductor technologies with high areal coverages and strain-limiting behavior: demonstration in high-efficiency dual-junction GaInP/GaAs photovoltaics

Notched islands on a thin elastomeric substrate serve as a platform for dual-junction GaInP/GaAs solar cells with microscale dimensions and ultrathin forms for stretchable photovoltaic modules. These designs allow for a high degree of stretchability and areal coverage, and they provide a natural form of strain-limiting behavior, helping to avoid destructive effects of extreme deformations.     

Growth of order/disorder heterostructures in GaInP using a variation in V/III ratio

CuPt ordering, resulting in formation of a natural monolayer {111} superlattice, occurs spontaneously during organometallic vapor phase epitaxial growth of Ga_0.52In_0.48P. The degree of order is found to be a function of the input partial pressure of the phosphorus precursor (P_P) during growth. This is thought to be mainly due to the effect of P_P on the surface reconstruction. A change in order parameter is associated with a change in the bandgap energy. Thus, a practical application of ordering is the production of a heterostructure by simply changing the flow rate of the P precursor during growth. Examination of transmission electron microscopy data and photoluminescence spectra indicates that order/disorder (O/D) (really less ordered on more ordered) and D/O heterostructures formed by growth using PH₃ at a temperature of 620°C are graded over several thousands of Å: The ordered structure from the lower layer persists into the upper layer. Similar results were obtained at 620°C when the first layer was grown using PH₃ (V/III=160) and the second using tertiarybutylphosphine (TBP) (V/III=5). The use of a temperature of 670°C to produce heterostructures using either PH₃ or TBP yields a totally different behavior. Abrupt D/O and O/D heterostructures can be produced by changing P_P during the growth cycle. The cause of this difference in behavior is not entirely clear. However, it appears to be related to a very slow change in the surface reconstruction, measured using surface photo absorption, when the PH₃ partial pressure is changed at 620°C.     

Step structure during organometallic vapor phase epitaxial growth of ordered GaInP

The nature of the steps on the nominally (00l)-oriented surface of Ga_0.5In_0.5P lattice matched to GaAs has been studied using high resolution atomic force microscopy. The layers were grown by organometallic vapor phase epitaxy (OMVPE) at a temperature of 620°C on substrates misoriented by angles,?_m, from 0 to 9° toward the $[\bar 110]$ direction in the lattice. An array of bunched steps from 25 to 50Å in height, depending on the substrate misorientation angle, is observed on the surface. An unusual feature of these bunched or super-steps, as compared to those seen for GaAs surfaces, is that they have relatively short lengths of a few thousand Angstroms. In addition, not all of the steps congregate into the surface steps. Thus, the surface consists of three “phases”: (001) flats, (11n) facets, and misoriented areas covered by an array of monolayer steps. The fraction of steps contained in the supersteps decreases monotonically as ?_m increases from 3 to 9°. Again, this differs from reports of the nature of GaAs surfaces grown under similar conditions where essentially all of the steps congregate into supersteps. The value of n for the (lln) facets also varies with misorientation angle: The angle between the (001) and the (lln) facets increases from approximately 11-12° for ?_m = 3° to nearly 30? for ?_m = 9°. An attempt was made to correlate the surface structure with ordering, which is observed to vary significantly with misorientation angle. The degree of order is found to increase monotonically with the fraction of steps forming supersteps.