POLYCRYSTALLINE THIN FILM SOLAR CELLS:Present Status and Future Potential (original) (raw)

Advances in CuInSe2 and CdTe thin film solar cells

Solar Cells, 1991

Research on CuInSe2 and CdTe thin film solar cells is discussed. CuInSe2 was deposited by selenization of Cu/In layers and was used to make a 109/0 efficient CuInSe2/(CdZn)S cell. Characterization of the reaction mechanisms is described. The open-circuit voltage Voc of CuInSe2/(CdZn)S cells is dominated by recombination in the space charge region, so increasing the band gap or decreasing the width of this region should increase Voc. Increasing the band gap with a thin Cu(InGa)Se2 layer at the CuInSe2 surface has demonstrated increased Voc with collection out to the CuInSe2 band gap. A post-deposition treatment and contacting process for evaporated CdS/CdTe cells was developed and high efficiency cells were made. Several steps in the process, including a CdC12 coating, a 400 °C heat treatment, and a contact containing copper are critical. ZnTe films were deposited from an aqueous solution as a contact to CdTe. 0379-6779/91/$3.50

EASILY REALIZABLE HETEROJUNCTION CdS/CuInSe2 FOR THIN FILMS PHOTOVOLTAIC APPLICATION

Chalcogenide Letters

A heterojunction based on cadmium sulfide (CdS) deposited on copper and indium selenide (CuInSe2) can be achieved by simple, easy to implement and low cost techniques. Homogeneous CuInSe2 layers were successfully deposited in an electrochemical way. The Raman and XRD analyses confirmed that the deposited films are mostly made of CuInSe2. Transmittance spectra analysis indicated that optical indices and gap energy correspond to those of CuInSe2. Chemical bath deposition of CdS onto CuInSe2 provides an heterojunction. I(V) characteristics of Ag/CdS/CuInSe2/Mo structure present a curve comparable to that of a silicon diode. Such a structure is then ready for photovoltaic application.

A comprehensive picture of Cu doping in CdTe solar cells

Journal of Applied Physics, 2013

The importance of Cu for CdTe solar cell absorber doping has been increasingly recognized in recent years. Currently different models are being discussed how to understand the case of Cu Cd substitutional doping in polycrystalline CdTe solar cells. In this work, an understanding is developed, which is based on a low concentration deep acceptor doped CdTe layer (N a $ 5 Â 10 14 cm À3 ,E a $ 300 meV above the valence band). Despite their non-shallow nature, Cu Cd acceptors are fully or at least heavily (>30%) ionized. The low hole concentration in CdTe ($1 Â 10 14 cm À3) originates directly from low Cu solubility in CdTe bulk material and is not caused by partial ionization or compensation as proposed by earlier models. The three to four orders of magnitude difference between bulk acceptor concentration and average Cu concentration in polycrystalline CdTe is attributed to grain boundary segregation of Cu. Our model is derived from substrate and superstrate CdTe solar cell measurements, controlled CdTe doping and quenching, Hall Effect measurements of CdTe films, numerical and analytical calculations, and a broad literature survey. Based on these results, routes to improve the conversion efficiency of CdTe solar cells are discussed. V

The photoresponse of CdS/CuInSe2 thin-film heterojunction solar cells

Ieee Transactions on Electron Devices, 1984

The effect of light bias on the spectral current response and spectral capacitance characteristics of CdS/CuInSe2 thin-film heterojunction solar cells has been investigated. Monochromatic light bias has been used to identify specific wavelength regions responsible for the spectral behavior seen under white light bias. Variations with light or voltage bias are consistent with the effect of the field on interface recombination in both high and low CdS resistivity devices. Devices with high CdS resistivity show spectrally dependent enhancement and quenching effects very similar to those reported for CdS/Cu2S devices in which the space charge region was primarily in the CdS. It is concluded that in high CdS resistivity devices the junction behavior is controlled by the photoconductive CdS as has been established in CdS/Cu2S cells. Low CdS resistivity CdS/CuInSe2 devices show none of these effects.

Cadmium Telluride/Cadmium Sulfide Thin Films Solar Cells: A Review

ES energy & environment, 2020

The efficiency and steadiness of solar cells are dependent on the experimental conditions during the fabrication of the device. In the present review, development in the last few decades in CdTe/CdS solar cells on different conducting substrates, their characterizations, and their effect on their performances has been illustrated. The variations in the efficiency were observed for the CdTe/CdS solar cells because of not only different deposition methods but also the difference in deposition conditions. In addition to this contact, material plays a significant role in the performance of a solar cell. CdTe/CdS solar cells with cheaper, greater efficiency can be possible soon.

The photoresponse of CdS/CuInSe2thin-film heterojunction solar cells

IEEE Transactions on Electron Devices, 2000

Zr/Pi/Ag samples and only 25 percent of the cells with the amorphous silicon layer. The Ti/Pd/Ag metallization withstood a 2-lb pull on soldered tabs while the other versions failed at about 1 lb. Five thermal cycles to -18OoC causedlittle damage to either the Ti or Zr metallizations but extensive delamination occurred on the &-Si cells. However, it is possible that the cell with the Ti/Pd/a-Si/Ag metallization could be improved by eliminating the break in vacuum between the silicon and metal depositions.

Cu-related recombination in CdS/CdTe solar cells

Thin Solid Films, 2008

Cu used in the back contact of CdS/CdTe solar cells is known to improve contact behavior and open-circuit voltage. A study of devices made with varying Cu amounts confirmed these observations. However, Cu was also found to be deleterious to current collection. Time-resolved photoluminescence measurements of CdTe devices show that carrier lifetime decreased with increased Cu concentration. Drive-level-capacitanceprofiling and low-temperature photoluminescence suggest this decrease in lifetime was associated with increased recombination center density introduced by Cu in the CdTe layer. The resulting impact of increased Cu on device performance was a voltage-dependent collection of photogenerated carriers that reduced fill-factor.

Low-cost deposition of CuInSe 2 (CIS) films for CdS/CIS solar cells

Solar Energy Materials and Solar Cells, 1998

We discuss in this paper the development of inexpensive, high efficiency, large-area solar cells of the type thin-film ZnO/CdS/Cu(In,Ga)Se . It has been shown recently in research laboratory tests that polycrystalline thin-film cells of this general composition deposited onto inexpensive soda-lime glass substrates have solar-to-electric conversion efficiencies exceeding 17%. These small-area cells were deposited using vacuum technology which is difficult and expensive to scale up in area to square-meter flat-plate modules in a manufacturing arena. We discuss in this paper inexpensive, non-vacuum deposition technology which is inherently scalable to largearea deposition. We pay particular attention to electrodeposition of multilayer binary or ternary selenide precursors to be thermally annealed to form Cu(In,Ga)Se films of appropriate overall composition, elemental grading and smoothness.