Atomic layer deposition enabling higher efficiency solar cells-Bram Hoex-solarbe文库

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Faculty of Engineering School of Photovoltaic and Renewable Energy Engineering Atomic layer deposition enabling higher efficiency solar cells 15 th -CSPV, Shanghai, 21 November 2019 Bram Hoex 1 , Kean Thong Khoo 1 , Xin Cui 1 , Geedhika Poduval 1 , Tian Zhang 1 , Xiang Li 2 , Wei Min Li 2 , and Md. Anower Hossain 1 1 School of Photovoltaic and Renewable Energy Engineering, UNSW Sydney, Sydney, Australia 2 Jiangsu Leadmicro Nano-Equipment Technology Ltd., Wuxi, ChinaSPREE PV research overviewSPREE PV research overview4 SPREE research overview ALD enabling high-efficiency solar cells Improving carrier selectivity on c-Si by ALD AlO x capping layers Improving NiO hole contacts for Si and perovskite solar cells Surface passivation of CZTS solar cells Conclusions OutlineResearch Question In principle, single sided deposition is very hard to achieve and parasitic deposition onto the front side of the solar cell can occur during fabrication. This has been reported for both PECVD and ALD AlO x deposition processes. 1 What is the effect of AlO x wrap-around on screen-printed contact resistance i.e., selectivity 2 What is the effect of AlO x wrap on p-PERC solar cell performance Source To, A. et al., IEEE JPV 2017 99 p. 1-8 5Methodology 1. Fabricate TLM test structures with intervening AlO x layers. Vary Paste, Temperature, Speed. The effect of AlO x wrap-around Processing sequence of the PERC and PERT precursors. Schematic diagram of the p-type PERC test structures used in this experiment. Source To, A. et al., IEEE JPV 2017 99 p. 1-8Contact resistivity ρ c – PERC Structures A clear ‘U’-shaped trend, representing an optimal firing temperature. Contact resistivity vs. temperature for screen-printed silver fingers fired through an AlO x /SiN x stack. 10 -3 10 -2 10 -1 10 0 10 1 10 2 10 3 10 4 10 5 10 6 10 7 10 8 Contact Resistivity [m Ω cm 2 ] 0 2575 Range within 1.5IQR Median Line Source To, A. et al., IEEE JPV 2017 99 p. 1-8Contact resistivity ρ c – PERC Structures A clear ‘U’-shaped trend, representing an optimal firing temperature. The addition of a 3 nm AlO x film on top of SiN x results in lower contact resistance. Firing temperature window appears larger and allows for lower firing temperatures. Contact resistivity vs. temperature for screen-printed silver fingers fired through an AlO x /SiN x stack. 10 -3 10 -2 10 -1 10 0 10 1 10 2 10 3 10 4 10 5 10 6 10 7 10 8 Contact Resistivity [m Ω cm 2 ] 0 2575 3 2575 Range within 1.5IQR Median Line Source To, A. et al., IEEE JPV 2017 99 p. 1-8Contact resistivity ρ c – PERC Structures A flatter ‘U’-shaped trend, representing an optimal firing temperature. The addition of a 5 nm AlO x film on top of SiN x still performs better than no AlO x capping layer. Contact resistivity vs. temperature for screen-printed silver fingers fired through an AlO x /SiN x stack. 10 -3 10 -2 10 -1 10 0 10 1 10 2 10 3 10 4 10 5 10 6 10 7 10 8 Contact Resistivity [m Ω cm 2 ] 0 2575 3 2575 5 2575 Range within 1.5IQR Median Line Source To, A. et al., IEEE JPV 2017 99 p. 1-8Contact resistivity ρ c – PERC Structures 10 nm AlO x capping layer on top of SiN x results in poor contact resistance for the investigated paste and firing conditions. Contact resistivity vs. temperature for screen-printed silver fingers fired through an AlO x /SiN x stack. 10 -3 10 -2 10 -1 10 0 10 1 10 2 10 3 10 4 10 5 10 6 10 7 10 8 Contact Resistivity [m Ω cm 2 ] 0 2575 3 2575 5 2575 10 2575 Range within 1.5IQR Median Line Source To, A. et al., IEEE JPV 2017 99 p. 1-811 Bifacial ALD AlO x layers tried in high volume manufacturing Significantly higher performance compared to monofacial counterpart Lower cost of ownership while adding one layer Implementation in high-volume manufacturing Source Hossain et al., Nano Material Science, 10.1016/j.nanoms.2019.10.001 21.0 21.5 22.0 0 5000 10000 15000 20000 25000 30000 35000 40000 Count Efficiency Bifacial PERC ALD Monofacial PERC PECVD12 SPREE research overview ALD enabling high-efficiency solar cells Improving carrier selectivity on c-Si by ALD AlO x capping layers Improving NiO hole contacts for Si and perovskite solar cells Surface passivation of CZTS solar cells Conclusions OutlineNovel Carrier Selective Contacts n-type Si E Fn E Fp J p J n NiO x TCO In 2O 3 H ITO E F Small ΔE v Large ΔE c  Transition metal oxides as selective contacts  Dopant free enables low temperature process  Better optical properties  Higher thermal stability than a-SiH possible [1] Battaglia et al., Appl. Phys. Lett. 2014 [2] Greiner et al., NPG Asia Mat. 2013 High work function 6 eV n-type Low valence band offset between Si p-type n-type Si E Fn E Fp D it d duced ba d be d g se ect e J p J n High WF Metal oxide MoO x WO x VO x TCO In 2O 3 H ITO E F[1] Menchini et al., Phys. Status Solidi C, 2016. Motivation and Approach -5 -4 -3 -2 -1 0 1 2 3 4 5 -10 -5 0 5 10 VoltageV Current mA RF sputtered NiO x Undesired S-shape [1] Atomic Layer Deposited ALD NiO x Very high resistance, Zener diode performanceSource Zhang et al., Appl. Phys. Lett. 113, 262102 2018 Motivation and Approach  DFT density functional theory calculation Yellow Green atoms Ni Purple atoms O Blue atoms Zn  NiO, cubic rock-salt structure  A 2x2x2 supercell, 64 atomsMotivation and Approach  Zn incorporation into NiO Additional electronic states contribution from the Zn 3d at the VBM Decreased band gap 3.2 eV to 2.9 eV  DFT density functional theory calculation VBM VBM CBM CBM Source Zhang et al., Appl. Phys. Lett. 113, 262102 2018ALD Process BisN,N -di-t-butylacetamidinato nickelII, NiAMD, 125 ℃ Diethyl Zinc, DEZ H 2 O Source Zhang et al., Appl. Phys. Lett. 113, 262102 2018ALD Process NiAMD DEZn H 2 O H 2 O Purge Time Supercycle A1B1m A2B2nx x supercycle m cycles n cycles Source Zhang et al., Appl. Phys. Lett. 113, 262102 2018 10 11 12 13 3 4 5 Thickness nm Supercycle numberALD Process NiAMD DEZn H 2 O H 2 O Purge Time Supercycle A1B1m A2B2nx x supercycle m cycles n cycles 0 1 2 3 4 0 1 2 3 mn561 1cycle ZnO 56 cycle NiO Thickness nm 0 1 2 3 4 0 1 2 3 0 1 2 3 4 5 6 7 8 0 1 2 3 0 1 2 3 4 5 6 7 8 9 10 0 1 2 3 mn561 1cycle ZnO 56 cycle NiO Thickness nm Thickness nm mn201 mn101 Thickness nm Supercycle number Source Zhang et al., Appl. Phys. Lett. 113, 262102 2018Contact performance  Cox Strack method 3.5 nm Zn x Ni 1-x O films with three different Zn concentrations -40 -20 0 20 40 -80 -40 0 40 80 Voltage mV Current mA increasing dot size  Good Ohmic contact was obtained from the structure  Contact resistivity 55 m Ω∙cm 2 Zn 0.62 Ni 0.38 O Source Zhang et al., Appl. Phys. Lett. 113, 262102 2018Thermal stability  Step-wise annealing in N 2 gas from room temperature to 500 o C for 10 min at each temperature  200 o C annealing improved the contact performance  Lowest contact resistivity 21.5 m Ω∙cm 2  The films are highly thermal stable RT 200 220 250 300 400 500 20 30 40 50 60 Contact resistivity mΩ.cm 2 Temperature °C Zn 0.46 Ni 0.54 O Zn 0.09 Ni 0.91 O Zn 0.62 Ni 0.38 O Source Zhang et al., Appl. Phys. Lett. 113, 262102 201822 SPREE research overview ALD enabling high-efficiency solar cells Improving carrier selectivity on c-Si by ALD AlO x capping layers Improving NiO hole contacts for Si and perovskite solar cells Surface passivation of CZTS solar cells Conclusions OutlineCurrent status and development of CZTS Benefits and Weakness Earth-abundant, Environmentally-friendly, low cost material Bandgap 1.5 eV for tandem, absorption 10 4 cm -1 Large V oc deficit Large V oc deficit from Bulk defects and disorder in the CZTS Unfavourable heterojunction band alignment Interface defects induced recombination [1] A. Polman et al. , Science, 2016. [1]Interface passivation via ALD-Al 2 O 3 [1]. Benick, J., et al., Applied Physics Letters, 2008. [2]. K. E. Roelofs, et al.,J. Phys. Chem. C, 2013. [3]. Koushik, D., et al., Energy Environ. Sci., 2017. Method – thermal ALD-Al 2 O 3 Motivation [1] [2] [3] Silicon solar cell Quantum dot sensitized solar cells Perovskite solar cell Al CH 3 O H TMA exposure Ar purge H 2 O exposure Ar purgeglass Mo CZTS ZnSnO i-ZnO ITO glass Mo CZTS CdS i-ZnO ITO Previous work on CZTS/ZnSnO solar cell CZTS E C ZnO E V ZnO ZnO SnO X 0.13 X 0.18 X 0.20 X 0.31 CdS Source Cui, X., et al., Chemistry of Materials, 2018.Passivation effects – Different cycles of ALD Al 2 O 3 0 2 4 6 8 10 Efficiency 20 30 40 50 60 70 Fill factor 12 14 16 18 20 22 J SC mA/cm 2 560 600 640 680 720 V OC mV glass Mo CZTS ZnSnO i-ZnO ITO glass Mo CZTS ZnSnO i-ZnO ITO AlOx Source Cui, X., et al., Energy Environ. Sci.,12, 2751 2019Passivation effects – Sub-steps of ALD Al 2 O 3 TMA exposure CZTS Ar purge CZTS Ar purge CZTS H 2 O exposure CZTS One cycle of ALD Al 2 O 3 150 o C vacuum heat Device performance 7 8 9 10 50 55 60 65 70 Fill factor J SC mA/cm 2 660 680 700 720 740 V OC mV Efficiency 18 20 22 Source Cui, X., et al., Energy Environ. Sci.,12, 2751 20190.0 0.2 0.4 0.6 0 4 8 12 16 20 0.0 0.2 0.4 0.6 0 4 8 12 16 20 0.0 0.2 0.4 0.6 0 4 8 12 16 20 Current density mA/cm 2 Voltage V η V OC J SC FF mV mA/cm 2 Al 2 O 3 10.2 736 21.0 65.8 Full Area ZnSnO 9.3 720 20.5 63.5 Current density mA/cm 2 Voltage V Current density mA/cm 2 Voltage V Efficiency improve from 9.3 to 10.2, record for Cd-free CZTS solar cell Benefits mainly from increased V oc and FF Record efficiency in Cd-free CZTS solar cell Source Cui, X., et al., Energy Environ. Sci.,12, 2751 201929 Thin ALD AlO x capping layers can decrease contact resistance You can reduce total cost of ownership by adding one nanoscale thin film to a PERC solar cell Doping of ALD NiO is straightforward and can significantly improve its conductance performance as hole selective contact ALD Al 2 O 3 enables world-record Cd-free CZTS solar cells Summary https//unswhoexgroup.com/ b.hoexunsw.edu.au 10 -3 10 -2 10 -1 10 0 10 1 10 2 10 3 10 4 10 5 10 6 10 7 10 8 Contact Resistivity [m Ω cm 2 ] 0 2575 3 2575 5 2575 10 2575 Range within 1.5IQR Median Line RT 200 220 250 300 400 500 20 30 40 50 60 Contact resistivity mΩ.cm 2 Temperature °C Zn 0.46 Ni 0.54 O Zn 0.09 Ni 0.91 O Zn 0.62 Ni 0.38 O 0.0 0.2 0.4 0.6 0 4 8 12 16 20 0.0 0.2 0.4 0.6 0 4 8 12 16 20 0.0 0.2 0.4 0.6 0 4 8 12 16 20 Current density mA/cm 2 Voltage V η V OC J SC FF mV mA/cm 2 Al 2 O 3 10.2 736 21.0 65.8 Full Area ZnSnO 9.3 720 20.5 63.5 Current density mA/cm 2 Voltage V Current density mA/cm 2 Voltage Vwww.pvsec-31.com pvsec31arinex.com.au 12 – 17 December 2021 We look forward to welcoming you to Sydney, Australia 31st International Photovoltaic Science and Engineering Conference