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RESEARCH AND DEVELOPMENT ON SPRAYED CDS-CUINSE2 THIN FILM SOLAR CELLS.

Objective

THIS WORK IS A PART OF AN EUROPEAN RESEARCH PROGRAMME ON CHALCOPYRITE SEMICONDUCTORS IN THE GOAL TO FABRICATE CDS-CUINSE2 SOLAR CELLS ENTIRELY SPRAYED.
The development of efficient thin film solar cells based on compound semiconductors, and ,in particular, chalcogenides and chalcopyrites, has been investigated with particular regard to the relevant material and device parameters. The preparation of thin films by low cost deposition techniques such as evaporation, sputtering, spray pyrolysis, selenisation and laser recrystallisation has been studied.
THE PURPOSE OF THIS RESEARCH WORK WAS THE ELABORATION OF LOW COST SOLAR CELLS BY THE WAY OF A NON SOPHISTICATED METHOD WHICH INVOLVES A CHEMICAL SPRAY PYROLYSIS PROCESS. THE BACKWALL SOLAR CELL IS CONSTITUTED BY A STACK OF LAYERS AS FOLLOWS: I.T.O./DOPED CDS/CDS/CU|NSE2/TOP CONTACT.
DIFFERENT STUDIES WITH TWO DIFFERENT SPRAY APPARATUS WERE UNDERTAKEN IN THE GOAL TO OBTAIN GOAD QUALITIES SPARYED LAYERS WITH CRYSTALLINITY AND PHYSICAL PROPERTIES QUITE SIMILAR TO THOSE OBTAINED AN EVAPORATED MATERIALS. THE ABSORBER LAYER IS THE MORE CRITICAL TO OBTAIN HIGH SHORT CIRCUIT CURRENT: AFTER DIFFERENT TESTS THE USE OF TWO THIN CU|NAW2 LAYERS IN PLACE OF ONLY ONE WAS NEEDED TO OBTAIN A SIGNIFICANT EFFICIENCY. WE HAVE SHOWN THAT THE SHORT CIRCUIT CURRENT VALUE WAS CLOSELY RELATED TO THE VARIATION OF THE ATOMIC RATIO OF THE FIRST ACTIVE CULNSE2 LAYERS IN PLACE OF ONLY ONE WAS NEEDED TO OBTAIN A SIGNIFICANT EFFICIENCY. WE HAVE SHOWN THAT THE SHORT CIRCUIT CURRENT VALUE WAS CLOSELY RELATED TO THE VARIATION OF THE ATOMIC RATIO OF THE FIRST ACTIVE CULNSE2 LAYER (WHICH IS CLOSED TO CDS) WHEREAS THE PHOTOVOLTAGE IS PRACTICALLY CONSTANT WITH A VALUE BETWEEN 250 AND 270 MV. HOWEVER THIS PHOTOVOLTAGE VALUE IS LOW COMPARED TO VALUES OBTAINED BY OTHER FABRICATION METHODS ESPECIALLY THERMAL EVAPORATION. AN IMPROVEMENT IN THE JUNCTION INTERFACE INCREASES THE PHOTOTENSION: EFFECTIVELY THE SURFACE MORPHOLOGY OF THE ACTIVE CDS LAYER NEAR THE JUNCTION IS DISRUPTED BY AGLOMERATE OF DISORIENTED CRYSTALLITES. A DECREASE IN THE CDS AND DOPED CDS THICKNESSES AND ALSO THE USE OF ANOTHER DOPANT IN INSTEAD OF A| FOR THE DOPED CDS LAYER ENHANCES THE OPEN CIRCUIT VOLTAGE. MOREOVER THE USE OF THE SAME APPARATUS (NAMED B) WITH A LINEAR SPRAY SWEEPING TO SPRAY ALL THE PHOTOCELLS LAYERS INSTEAD OF ONE (NAMED A) TO SPRAY THE CDS LAYERS AND ANOTHER ONE(NAMED B) TO SPRAY THE I.T.O. AND CULNSE2 FILMS IMPROVES THE PHOTOVOLTAIC PARAMETERS. HOWEVER A FURTHER OPTIMIZATION OF EACH CDS LAYER WAS NEEDED PARTICULARY BY ACTING ON THE MOLAR CONCENTRATION AND ADJUSTING THE (IN) DOPANT CONCENTRATION IN THE WAY TO DECREASE THE CDS RESISTIVITY.
AT THAT TIME THE BEST EFFICIENCY OBTAINED ON 1 CM2 AREA IS 3.6% WITH ISC = 31 MA, VOC = 275 MV, FF = 0.42. THESE VALUES ARE VERY REPRODUCIBLE.

Funding Scheme

CSC - Cost-sharing contracts

Coordinator

Université de Montpellier II (Université des Sciences et Techniques du Languedoc)
Address
2 Place Eugène Bataillon
34095 Montpellier
France