Atmospheric spatial atomic layer deposition of ZnOS buffer layers for flexible Cu(In,Ga)Se2 solar cells

Abstract

Zinc oxysulfide (ZnOS) is synthesized at atmospheric pressure in a laboratory-scale spatial atomic layer deposition setup by sequentially exposing the substrate to diethyl zinc and an H2O/H2S mixture, separated by a nitrogen gas curtain. The co-injection of H2O and H2S vapors in the same deposition zone enables an accurate control of the S/(O + S) ratio, the morphology, and the optoelectronic properties of the films. Next, the ZnOS deposition process is transferred to an industrial roll-to-roll spatial-ALD setup. ZnOS is applied as a buffer layer in flexible Cu(In,Ga)Se2 solar cells, instead of the commonly used CdS, achieving a best efficiency of typically 13% in small area cells (0.57 cm2) and 9.2% in flexible mini-modules (270 cm2). These results show the viability of atmospheric spatial-ALD as a new technique for roll-to-roll manufacturing of flexible photovoltaics modules based on a Cu(In,Ga)Se2 absorber.

In-situ observation of nucleation and property evolution in films grown with an atmospheric pressure spatial atomic layer deposition system

“…Growing interest in spatial ALD has led to several review papers in recent years [3][4][5][6], and companies such as Levitech, Beneq, and SoLayTec have commercialized spatial ALD systems. Both metal oxides and metals have been deposited [4,5,7], and AP-SALD and AP-CVD films have been utilized in thin film transistors [8,9], metal-insulator-metal diodes [10], photovoltaic devices [2,[11][12][13][14][15][16][17], and LEDs [18][19][20]. Yet despite the promise of these techniques, little has been done to characterize the nucleation and property evolution of these nanoscale films.…”

Thickness evaluation of AlOx barrier layers for encapsulation of flexible PV modules in industrial environments by normal reflectance and machine learning

“…The system described above was employed on different sets of samples for the evaluation of the thickness of nanometric AlO x layers deposited by means of a laboratory‐scale rotary spatial ALD reactor 31 on relevant substrates for the PV industry: (i) three monocrystalline Si substrates coated with 25‐, 50‐, and 75‐nm AlO x layers; (ii) six 15 × 15‐cm 2 complete (nonencapsulated) flexible Cu(In,Ga)Se 2 thin film PV devices (on polyimide foil substrate with Mo back electrode, CdS buffer layer and Al‐doped zinc oxide front electrode) with 15‐, 25‐, 30‐, 50‐, 60, and 75‐nm AlO x layers (referred to as “CIGS” in the text and figures); and (iii) six 15 × 15‐cm 2 PET foil samples with 15‐, 25‐, 30‐, 50‐, 60‐, and 75‐nm AlO x layers. It should be noted that these thicknesses should be taken only as nominal deposition values.…”

Atmospheric-pressure atomic layer deposition: recent applications and new emerging applications in high-porosity/3D materials

“…An array of mini-modules with a surface area of 270 cm 2 on a flexible substrate was demonstrated with a cell efficiency of 9.2%. 65 The main advantage of organic solar cells lies in the flexibility of polymers, making them mass-manufacturable on various flexible substrate materials. 113 Theirich et al 30 reported on the deposition of TiO x by plasma-enhanced atmospheric-pressure s-ALD at room temperature as the interlayer in inverted organic solar cells which performed similarly to those containing TiO x films prepared by conventional ALD or sol-gel processing.…”

“…An array of mini-modules with a surface area of 270 cm 2 on a flexible substrate was demonstrated with a cell efficiency of 9.2%. 65 The main advantage of organic solar cells lies in the flexibility of polymers, making them mass-manufacturable on various flexible substrate materials. 113 …”