Comparative study of water and ammonia rinsing processes of potassium fluoride-treated Cu(In,Ga)Se<sub>2</sub>thin film solar cells

Progress in Photovoltaics

Matsuura

Sugiyama

et al. 2018

Self Cite

The combined effect of heating and forward bias voltage, that is, heat‐bias soaking (HBS) on cesium fluoride (CsF)‐free and CsF‐treated Cu(In1‐xGax)Se2 (CIGS) solar cells using chemical bath deposition‐cadmium sulfide (CBD‐CdS) buffer layer was investigated with varying the heating temperature, bias voltage, and biasing time. Heat bias soaking followed by heat soaking (HS) (ie, HBS/HS) treatments improved the open‐circuit voltage (VOC) and conversion efficiency for the CsF‐treated CIGS solar cell, whereas such a beneficial effect was not observed for CsF‐free CIGS solar cells. Capacitance‐voltage measurement confirmed the significantly increased carrier concentration (NCV) after HBS for the CsF‐CIGS solar cell, which is one of the possible reasons for the increased VOC. Because of the extremely high NCV, the short‐circuit current density (JSC) decreased owing to the narrower depletion width. However, the high NCV could be tuned to an appropriate value via a subsequent moderate heating procedure without biasing. As a result, the JSC loss was reduced, thereby improving the cell efficiency. These results open a new route to improve the efficiency of alkali‐treated CIGS solar cells.

Section: Resultsmentioning

confidence: 98%

Section: Sims Analysis Of Csf-treated Cigs Solar Cells Before and Amentioning

confidence: 92%

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Effect of heat‐bias soaking on cesium fluoride‐treated CIGS thin film solar cells

Progress in Photovoltaics

Matsuura

Sugiyama

et al. 2018

Self Cite

“…[4] Recently, there have been several reports on improving the efficiency of CIGS solar cells via surface modification by alkalimetal treatments. [16][17][18][19][20][21][22][23][24][25][26][27][28][29] The heavy alkali metals (Rb and Cs) are expected to be more effective than (K and Na) owing to better diode quality. [30][31][32] Current world-record devices have been obtained after Rb and Cs treatments.…”

mentioning

confidence: 99%

Proton Irradiation on Cesium‐Fluoride‐Free and Cesium‐Fluoride‐Treated Cu(In,Ga)Se₂ Solar Cells and Annealing Effects under Illumination

Physica Rapid Research Ltrs

Lin

Nakada

et al. 2019

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Several studies have been performed on proton irradiation onto alkali‐metal untreated Cu(In,Ga)Se2 (CIGS) solar cells. However, there are almost no studies describing similar effects on alkali‐treated CIGS solar cells. With this motivation, this work investigates proton irradiation and annealing effects under illumination on cesium‐fluoride‐free (CsF‐free) and CsF‐treated CIGS solar cells. Both CsF‐free and CsF‐treated CIGS solar cells degrade under proton irradiation. External quantum efficiency measurements show degradation in long wavelengths after the treatment. The experimental data are fitted with a simulation, which show that proton‐irradiated degradation is more severe at high fluence. Capacitance–voltage measurements show a broadening of the depletion region after proton irradiation, which is due to the decreased net carrier concentration. It is proposed that proton irradiation at low fluence generates shallow‐type defects, whereas high‐fluence protons generate deep defects. However, it is observed that room‐temperature storage of the proton‐irradiated solar cells causes partial recovery. Thermal annealing under illumination treatments is found to be beneficial to the drastic recovery of the performance of solar cells irradiated at low fluence. High‐fluence proton‐irradiated solar cells undergo minor recovery.

“…It is confirmed from this experiment that V OC improvement was inferior to ammonia-rinsed CIGS solar cell than that of DI water-rinsed CIGS solar cell, which may be due to the reduction of Cs-containing Cu-depleted layer from the surface. [17,45] This results further suggest that the alkali-contained new layer plays an important role in metastable behavior in the CsF-treated CIGS solar cells.…”

Section: Ishwor Khatri* Takahiko Yashiro Tzu-ying Lin Mutsumi Sugimentioning

confidence: 79%

Metastable Behavior on Cesium Fluoride‐Treated Cu(In_1–x,Ga_x)Se₂ Solar Cells

Physica Rapid Research Ltrs

Yashiro

Lin

et al. 2020

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Metastable behavior of cesium fluoride (CsF)‐treated Cu(In1–x,Gax)Se2 (CIGS) solar cells is investigated under heat‐light soaking (HLS) and heat‐soaking (HS) treatments. HLS increases open‐circuit voltage, fill factor, efficiency, and net carrier concentration and decreases short‐circuit current density, whereas heat‐soaking treatment acts oppositely. The performance of a CsF postdeposition treatment to CIGS thin film in selenium vapor, and closer to stoichiometry copper content, did not mitigate the open‐circuit voltage improvement after HLS. These results argue the traditional concept of the VSe–VCu divacancy complex for the total beneficial effect of HLS in alkali‐treated CIGS solar cells. The metastable behavior observed in the CsF‐treated devices due to the HLS and HS treatments is explained by the specific behavior of alkali‐containing new compounds at the surface and/or the migration of alkali metals at the surface and bulk regions.