摘要:

An overview is presented of results obtained recently by my group on the effect of point defects on the conduction properties ofCu(In1−xGax)Se2.(CIGS) An interpretation of the data is presented suggesting that clustering of majority point defects into superclusters. This leads to uncompensated defects around the perimeter of the superclusters. These may account for one type of acceptor in the material. The other acceptor is proposed to beCuIn,a minority defect. It is suggested based on electrical results that Ga increases formation of defects. The observed compensating donor is proposed to be unpairedInCu.It is shown that these donors are removed by Na impurities. Finally, a discussion of ion implant damage is presented. It is argued that the mobility of holes in CIGS should be at least 100 cm2/V-s in good materials. ©1999 American Institute of Physics.

ISSN:0094-243X    

DOI:10.1063/1.57960

出版商:AIP    

年代:1999

数据来源: AIP

摘要:

The principles of x-ray fluorescence (XRF), and differences between the use of XRF as anin-situcomposition sensor in CIGS module fabrication and the use of XRF in typical applications, are described. It is demonstrated for measurements on CIGS samples how a number of conditions, including interelement effects and composition gradients, may complicate conversion of XRF signals to composition. Factors controlling the precision of the measurement are enumerated. ©1999 American Institute of Physics.

ISSN:0094-243X    

DOI:10.1063/1.57961

出版商:AIP    

年代:1999

数据来源: AIP

摘要:

The evolution of EPV’s CIGS process development is described, culminating in the invention of the high voltage FORNAX process. Cell, minimodule, and module results are given, together with a description of the use of a non-destructive technique to quantify intrinsic device and sheet resistance contributions to module fill factor. ©1999 American Institute of Physics.

ISSN:0094-243X    

DOI:10.1063/1.57962

出版商:AIP    

年代:1999

数据来源: AIP

摘要:

The role of Ga in CIGS solar cells is complex. In addition to its primary role of alloying agent to increase the band gap we also observe its influence on passivation, transport, trapping and doping. At low levels it can positively influence all of these mechanisms and improve performance. As its level is increased, there are complex tradeoffs among these that must be controlled to maintain good performance. We have applied photocapacitance techniques to study the junction interface region and the role that Ga plays in its formation and operation. We observe a correlation between the defect that provides doping and the recombination centers, which control Voc. The dominant centers are deep in the band gap and are located near the metallurgical junction. It is proposed that a reduction of the correlated doping defect will result in improved interface properties. ©1999 American Institute of Physics.

ISSN:0094-243X    

DOI:10.1063/1.57963

出版商:AIP    

年代:1999

数据来源: AIP

摘要:

A new technique for fabricating thin films ofCuInSe2and its alloys for low-cost photovoltaics has been developed. The technique uses simple, self-limiting, non-vacuum processes to prepare particulate precursor materials, to deposit layers of these precursor materials, and to convert the precursor layers intoCuInSe2films. An NREL confirmed 8.5&percent; efficient solar cell has been achieved withCuIn1−xGaxSe2in early research. The simplicity and low cost of the technique are well suited to manufacturing in a wide variety of settings, including in developing countries where industrial infrastructure is currently limited. ©1999 American Institute of Physics.

ISSN:0094-243X    

DOI:10.1063/1.57964

出版商:AIP    

年代:1999

数据来源: AIP

摘要:

Although 12&percent; to 14&percent; cells have been fabricated with highly resistive ZnO buffer layers grown by MOCVD, an improved understanding of the required processing to achieve high efficiency is still required. For example, it is found that it is beneficial to “age” i-ZnO/CIS cell structures in air for several weeks before completing the cell with a TCO and collector grid. SIMS depth concentration profiles have been acquired for i-ZnO/CIS film structures grown on polycrystalline CIS and also for epitaxial CIS grown on GaAs. These profiles clearly establish that Zn and oxygen diffuse along grain boundaries during ZnO growth, and probably in such a manner that the Zn concentration exceeds that of oxygen. It is proposed that the beneficial effect of air exposure in the aging process is due to additional oxygen diffusing along grain surfaces and combining with excess zinc such that recombination centers are passivated, and values of FF and Voc are increased. ©1999 American Institute of Physics.

ISSN:0094-243X    

DOI:10.1063/1.57965

出版商:AIP    

年代:1999

数据来源: AIP

摘要:

A systematic study of the stability of CdTe solar cells fabricated by SCI and NREL has been made. Cells were stressed at elevated temperatures under various bias conditions, both with illumination (∼2 suns) and in the dark. An activation energy of approximately 1 eV is implied from cells stressed at various elevated temperatures. The stability of CdTe solar cells was found to be bias dependent and device-specific. Cells made with thick CdTe and no back-contact copper as well as by at least one SCI recipe were very stable. Extrapolation of effects assuming Arrhenius behavior yields estimated lifetime expectations for the cells stressed at elevated temperatures. ©1999 American Institute of Physics.

ISSN:0094-243X    

DOI:10.1063/1.57895

出版商:AIP    

年代:1999

数据来源: AIP

摘要:

Cadmium sulfide continues to be the most successful and widely used n-type heterojunction partner in thin film CdTe solar cells. In most cases solar cell performance is enhanced if the CdS films are heat treated prior to the deposition of the CdTe. This paper discusses the effect ofH2annealing on the resistivity of CSS-CdS films and the use of a mobility activation model to explain the observed changes in resistivity. Photoluminescence measurements of CSS CdS films heat-treated in He and inCdCl2vapor have also been carried out. In all cases the heat treatments lead to an increase in the intensity of a photoluminescence band believed to be associated with sulfur vacancies. ©1999 American Institute of Physics.

ISSN:0094-243X    

DOI:10.1063/1.57966

出版商:AIP    

年代:1999

数据来源: AIP

摘要:

The influence of processing conditions on the performance of polycrystalline thin-film CdTe-based solar cells and the relationship to device stability are addressed. Specifically, processing conditions with respect to the window layer, post-CdTe deposition treatments, and contacting treatments are examined. The use of high resistivity interlayers between the transparent conductive oxide and the CdS allows open circuit voltage to be maintained as the CdS thickness is reduced. CdS-CdTe interdiffusion is reduced by either use of a short 600&hthinsp;°C anneal prior toCdCl2vapor treatment or by use ofCdTe1−xSxalloy absorber layers. Finally, the effects ofCdTe1−xSxsurface modification and Cu reaction on device current-voltage behavior are presented. ©1999 American Institute of Physics.

ISSN:0094-243X    

DOI:10.1063/1.57896

出版商:AIP    

年代:1999

数据来源: AIP

摘要:

We have investigated the optical and electrical properties of the CdS films under a variety of the post-deposition annealing treatments.CdCl2-treatment results in the decrease of the shallow defect density, the increase of the bandgap, the photoconductivity response, as well as the optical transmission in the wavelength range between 500 and 600 nm of the CdS films. While non-CdCl2-treatment (annealed withoutCdCl2) leads to the opposite results. Also, after coated with the CdTe films and annealed,CdCl2-treated CdS films of the annealed CdS/CdTe films have higher photoconductivity response than the as-deposited CdS films of the annealed CdS/CdTe films. The role ofCdCl2in the post-treatment and the influence of theCdCl2treatment on the CdTe/CdS cell performance is analyzed. ©1999 American Institute of Physics.

ISSN:0094-243X    

DOI:10.1063/1.57897

出版商:AIP    

年代:1999

数据来源: AIP