Thin film solar cell

Details Thin film solar cell Thin film solar cell

1996-11-25

1998-12-29

Chapman, Mark

Batteries: thermoelectric and photoelectric

Photoelectric

Cells

H01L 31075

Patent

active

058534989

DESCRIPTION:

BRIEF SUMMARY
CROSS REFERENCE TO RELATED APPLICATIONS

This application is a national phase of PCT/DE 95/00379 filed 17 Mar. 1995 and based, in turn, upon German application P 44 10220.8 of 24 Mar. 1994 under the International Convention.


FIELD OF THE INVENTION

The invention relates to a thin film solar cell based/amorphous hydrogenated silicon and/or its alloys and, more particularly, with at least one layer sequence of p-doped, undoped(i) and n-doped layers,especially a metallic layer bonded to the last n-doped layer.


BACKGROUND OF THE INVENTION

Thin film solar cells of amorphous hydrogenated silicon (a-Si:H) and/or its alloys are produced with a doping sequence n-i-p or p-i-n or in known variants (e.g. with additionally incorporated buffer layers) by layer deposition upon suitable opaque or transparent substrates. Such a solar cell thus can also be provided in the form of a stacked solar cell in a cascade arrangement (so-called stacked cell e.g. p-i-n-p-i-n).
In the case in which the light impingement is from the p-doped side because of different mobilities of the charge carriers n and p, an improvement in the efficiency y of the solar cell is attained.
To improve the light entry in the undoped (i)-layer dimensioned for the light conversion and also for electrical improvement, the band gap of the p-doped layer is advantageously selected to be higher than that of the i-layer. This can be realized for example by alloying the a-Si:H with N, C or O.
As a rule the contact layers at the light inlet side are transparent conductive oxide layers, so-called (TCO) layers, for example ITO, SnO.sub.2, ZnO, TiO.sub.2. At the side turned away from the light, a TCO layer can also be provided or a metal layer or a combination of the two can be chosen.
It is known that the TCO-p contact can make up a significant fraction of the total series resistance of an a-Si:H solar cell so that the so-called fill factor (FF) is disadvantageously reduced and the efficiency y of the solar cell is reduced.
In T. Yoshida et al., Proceedings 10th European PV Solar Energy Conference, Lisbon 1991, page 1193, to reduce the TCO-p contact resistance, the insertion of an SiOx "recombination layer" between the ZnO and p is proposed for the contact system ZnO-p. Quantitative results for the there-described conclusion of an improvement were not given.


OBJECT OF THE INVENTION

It is the object of the invention to provide a solar cell which, by contract with the known solar cells, especially for ZnO or TiO.sub.2 as TCO which will have a reduced TCO-p contact resistance which is desirable for a satisfactory efficiency y of the solar cell and an increased so-called fill factor FF (or an increased open circuit voltage V.sub.oc) associated therewith.


SUMMARY OF THE INVENTION

This object is achieved in a thin-film solar system with at least one layer sequence of p-doped, undoped(i) and n-doped layers, a TCO-layer neighboring the first p-doped layer and a contact layer, especially a metallic layer bonded to the last n-doped layer, wherein between the TCO layer and the p-doped neighboring same a small n-doped intermediate layer is provided and at least the intermediate layer or its neighboring p-doped layer is microcrystalline.
The insertion of an n-doped intermediate layer between the TCO and p-doped layer and the microcrystalline (.mu.c) configuration of the intermediate layer leads to an improved FF and increased no-load voltage V.sub.oc at the TCO, especially ZnO. It is advantageous, alternatively or cumulatively, to provide the p-doped layer as microcrystalline(uc).
For reducing or avoiding absorption losses, we may use as the material for the incorporated n-doped intermediate layer a material with increased band gap (for example .mu.c-SiC or .mu.c-SiO).
An especially advantageous embodiment of the solar cell of the invention is obtained is given when the layer thicknesses of the n- and p-layers are so selected that the total layer thickness of these two layers does not exceed the layer thickness of an optimum p-layer on the same (TCO--) substrate.
In t

REFERENCES:
patent: 4776894 (1988-10-01), Watanabe et al.
"High-efficiency double junction solar cells . . " by Yoshida et al., 10th EC Photovoltaic Solar Energy Conference, 8 Apr. 1993, pp. 1193, 1196.
"High mobility hydrogenated and oxygenated monocrystalline silicon . . . " by Faraji et al., Applied Physics Letter, vol. 60, No. 26, 29 Jun. 1992, pp. 3289-3291.
"An optimum design of a-Si/poly-Si tandem solar cell" 23rd IEEE Photovoltaic Conference, 10 May 1993, pp. 833-838.
"Transparent conducting electrons on silicon", by Kurtz et al, Solar Energy Materials, vol. 15, No. 4, May 1987, pp. 229-236.
"Modification of TCO-p interface in a-Si:H solar cells . . . " by Kubon et al., 12 European Photovoltaic Solar Energy Conference, 11 Apr. 1994, pp. 1268-1271.

Affiliated with

Also associated with

Rating

Thin film solar cell does not yet have a rating. At this time, there are no reviews or comments for this patent.

If you have personal experience with Thin film solar cell, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Thin film solar cell will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFUS-PAI-O-1420153