Presentation Details
| Role of Se composition and CdCl2 Treatment on Intrinsic Donor Defects in Polycrystalline CdTe-based PV Devices Sushmakanth Myneni, Daniel Shaw, Walajabad Sampath. Colorado State University, Fort Collins, CO, USA |
Abstract
Abstract — State-of-the-art P-type CdTe-based absorbers have a graded bandgap, with lower bandgap in the front enabled by Selenium (Se) alloying leads to improved Jsc. Se incorporation has also been associated with enhanced carrier lifetime and luminescence. However, direct evidence of improved Voc or FF due to Se passivation remains limited. This has been attributed to Se related defects that act as carrier traps and compensating donors. To better understand the origin of these intrinsic donor defects, in this study, we try to decouple Se composition and CdCl2 effects. By varying the CdCl2 duration on films under fixed Se concentration and varying the Se concentrations in the absorber under standard CdCl2 treatment. We report that CdTe (no Se) exhibited lowest (hole) carrier concentration, whereas absorbers with high Se concentrations exhibited highest (electron) carrier concentration despite no intentional doping, suggesting significant intrinsic donor densities in high Se content absorbers. Extended CdCl2 treatment reduced the (electron) carrier concentration in these absorbers, indicating a strong interaction between Cl and donor defects. Additionally, CdTe (no Se) exhibited least Urbach energy compared to devices with high Se concentration, this observation is in agreement with other studies. These results suggest that mitigating Se-related compensating donor defects is critical for further Voc enhancement in CdTe devices. At the same time, naturally high electron concentrations observed in high Se content absorbers may provide motivation for exploring n-type CdTe architectures.
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No part of this publication may be reproduced, distributed, or transmitted in any form or by any means, including photocopying, recording, or other electronic or mechanical methods, without the prior written permission of the author.
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