CdS versus ZnSnO buffer layers for a CIGS solar cell: a depth-resolved analysis using the muon probe

Eduardo Ribeiro,Thomas Prokscha,Rui C Vilão,João M Gil,Pedro M.P Salomé,Andreas Suter,Zaher Salman,Helena V Alberto,Alois Weidinger,B.G Almeida,J Agostinho Moreira

doi:10.1051/epjconf/202023305004

Abstract

The influence of a buffer layer in the surface of a Cu(In,Ga)Se2 (CIGS) solar cell material is studied using implanted positive muons as a probe. A depth resolved analysis of the muon data suggests that both CdS and ZnSnO reduce the width of a defect layer present at the CIGS surface to about half its original value. Additionaly, CdS is able to reduce the intensity of the distur¬bance in the defected region, possibly due to a surface reconstrution in CIGS.

Highlights

Thin film solar cells using Cu(In,Ga)Se2 (CIGS) as the p-type absorber achieved recently 23.3% solar cell efficiency[1], the highest value among multi-crystalline solar cells
A previous study [4] using implanted positive muons with energies in the range 2-24 keV has shown that the formation of the final bound configuration of the muon is sensitive to local barriers and that the spatial extent of the decrease in formation probability of the muon state can be used as a measure of the width of a defective region ocurring at the p-n interface
This paper presents the results obtained for low-energy muon data for a CIGS film and two junctions, CdS/CIGS and ZnSnO/CIGS reanalysed using this new method

Summary

Introduction

Thin film solar cells using Cu(In,Ga)Se2 (CIGS) as the p-type absorber achieved recently 23.3% solar cell efficiency[1], the highest value among multi-crystalline solar cells. CdS has been the most widely used n-type buffer layer for CIGS solar cell, but has the important disadvantage of containing a toxic element, the cadmium. A new method of analysis of the energy-dependent muon data was developed, allowing a depth-resolved analysis of all the experimental parameters associated with the muon signal [5]. This paper presents the results obtained for low-energy muon data for a CIGS film and two junctions, CdS/CIGS and ZnSnO/CIGS reanalysed using this new method. It is shown that this depth-resolved analysis provides new insights on the microscopic processes ocurring during the formation of the buffer/absorber interface in a CIGS based solar cell

Experimental Details and Data Analysis

Results and Discussion

Conclusions