Direct comparison of atomic layer deposition and sputtering of In2O3:H used as transparent conductive oxide layer in CuIn1−xGaxSe2 thin film solar cells

Self Cite

139

This contribution concerns the effect of the Ag content in wide‐gap AgwCu1‐wIn1‐xGaxSe2 (ACIGS) absorber films and its impact on solar cell performance. First‐principles calculations are conducted, predicting trends in absorber band gap energy (Eg) and band structure across the entire compositional range (w and x). It is revealed that a detrimental negative conduction band offset (CBO) with a CdS buffer can be avoided for all possible absorber band gap values (Eg = 1.0–1.8 eV) by adjusting the Ag alloying level. This opens a new path to reduce interface recombination in wide‐gap chalcopyrite solar cells. Indeed, corresponding samples show a clear increase in open‐circuit voltage (VOC) if a positive CBO is created by sufficient Ag addition. A further extension of the beneficial compositional range (positive CBO at buffer/ACIGS interface) is possible when exchanging CdS with Zn1‐ySnyOz, because of its lower electron affinity (χ). Nevertheless, the experimental results strongly suggest that at present, residual interface recombination still limits the performance of solar cells with optimized CBO, which show an efficiency of up to 15.1% for an absorber band gap of Eg = 1.45 eV.

Section: Resultscontrasting

confidence: 99%

Wide‐gap (Ag,Cu)(In,Ga)Se₂ solar cells with different buffer materials—A path to a better heterojunction

Keller

Sopiha

Stolt

et al. 2020

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139

“…Three TCOs are investigated here: (1) sputtered i‐ZnO/ZnO:Al (reference), (2) chemical vapor deposited (CVD) ZnO:B, and (3) sputtered In 2 O 3 :H. In this way, a change in deposition method as well as a change in material system can be compared. It was shown before, that by exchanging ZnO:Al with a ZnO:B TCO, the short circuit current density J SC can be increased, while for In 2 O 3 :H an improved J SC and V oc was observed . However, these studies were conducted on CIGSe solar cells, which were not subjected to a KF‐PDT step during processing.…”

Section: Introductionsupporting

confidence: 73%

“…It was shown before, that by exchanging ZnO:Al with a ZnO:B TCO, the short circuit current density J SC can be increased, 9 while for In 2 O 3 :H an improved J SC and V oc was observed. 10 However, these studies were conducted on CIGSe solar cells, which were not subjected to a KF-PDT step during processing.…”

Section: Introductionmentioning

confidence: 99%

Effect of KF absorber treatment on the functionality of different transparent conductive oxide layers in CIGSe solar cells

Keller

Chalvet

Joel

et al. 2017

Self Cite

“…Therefore, when incorporated in the front contact layers, In 2 O 3 ‐based materials can potentially generate higher conversion efficiency than ZnO‐based materials, and we demonstrate this concept with a ‐In‐Ga‐Zn‐O ( a ‐IGZO)/ a ‐In 2 O 3 :H front contact layers . Furthermore, several experimental studies revealed that In 2 O 3 ‐based TCOs reduced the electrical loss caused by series resistance and optical loss because of free carrier absorption within the TCO layer while improving the stability of solar cells and mini‐modules. Recently, Keller et al applied various TCO (ZnO:Al, ZnO:B, and In 2 O 3 :H) layers in CIGS solar cells with KF‐PDT .…”

Section: Introductionmentioning

confidence: 69%

Impact of front contact layers on performance of Cu(In,Ga)Se₂ solar cells in relaxed and metastable states

Koida

Nishinaga

Ueno

et al. 2018

We studied the impacts of front contact layers composed of transparent conducting oxide (TCO) and transparent oxide semiconductor (TOS) layers on the performance of Cu(In,Ga)Se 2 (CIGS) solar cells with glass/Mo/CIGS/CdS/TOS/TCO in relaxed and metastable states. After annealing under illumination, the CIGS solar cells with KF and NaF postdeposition treatments exhibited metastable increases in open-circuit voltage, fill factor, and the resulting conversion efficiency with a metastable decrease in short-circuit current density. These are partly attributed to an increase in metastable acceptor density in the CIGS layers, being stable for a day even at room temperature, with a reduced space charge width. We found that the net acceptor density evaluated by capacitance-voltage measurements largely varied depending on the TOS/TCO layers, whereas the open-circuit voltage was identical. On the other hand, no significant differences in both the net acceptor density and open-circuit voltage were observed regardless of the TOS/TCO layers in the relaxed state produced by annealing in the dark. The results suggest that the CdS/CIGS heterojunction can no longer be treated as an n + /p junction in the metastable state and that the evaluated acceptor density was apparent values with large difference originating from different potential distribution in the CdS layer, which is related to the TOS/CdS and TCO/CdS junctions. In addition, the TOS/TCO layers largely affected the short-circuit current density owing to their optical constants and film thicknesses. The presented results highlight the importance of the design of CdS/TOS/TCO layers in solar cells operated in metastable states.