Efficient Si nanowire heterojunction solar cells ...-王奉友-吉林师范大学.pdf

Efficient Si nanowires heterojunction solar cells with dopant-free carrier selective layers 王奉友 2018.11.08 Xi’an 吉林师范大学 功能材料物理与化学教育部重点实验室 E-mail: wfy@jlnu.edu.cn Outline 1. Motivation 2. Suppressing interface recombination 3. Design & fabrication of carrier transporting layer 4. Summary JLNU Jilin Normal University 1 *light-trapping *photo-generated carrier collection *quasi-omnidirectional… Hong et al. J. Appl. Phys. 2013, 114, 084303. Nanostructured Si heterojunction solar cells 33 % 1. Interface recombination l n( )v itBoc sc qN Snk TV q q J   High aspect ratio  Large roughness Devices performance↓ 2. Optical losses on HTL 20 nm p-a-Si:H (Eg ~ 1.8 eV) (1.7-3.5 eV): a-Si:H c-Si Parasitic absorption Surface passivation + HTL with wide Eg 2 H2 plasma treatment 0 10 20 30 40 50 60 70 80 90 100 100 200 300 400 500 600 Po li sh ed sub strate T extu r ed sub strate Mi norit y ca rr iers li f et im e (μs) H 2 - plas ma ex po rsu re ti me ( s) Improve lifetime / homogeneity→lower interface recombination Wang et al. ACS Appl. Mater. Inter. 2014, 6, 15098-15104. Substrate modification Wang et al. J. Mater. Chem. A, 2015, 3, 22902- 22907. Dangling bonds 1. Suppressing interface recombination TMAH treatment → smooth + remove metal ions→ lifetime↑ 3 Ultrathin SiOx passivation Aqueous assisted ultraviolet ozone treatment Conformal passivation→ lifetime↑ + homogeneity↑ Developing ultra-thin SiOx passivation Passivation Carrier transporting Tunneling at hetero-interface for high performance device 1.Suppressing interface recombination 4 Key factors for carrier transporting layer  √:High conductivity  √:Wide bandgap (reduce optical loss)  √:Bandgap alignment P-a-Si:H/nc-Si:H 400 600 800 1000 1200 0 20 40 60 80 100 E Q E ( %) W av el en g t h ( nm) J sc = 3 7 . 1 mA / c m 2 0.0 0.1 0.2 0.3 0.4 0.5 0.6 0 10 20 30 40 C u rre n t D e n si ty (mA/ cm 2 ) Vo l t a g e (V) V oc = 6 1 1 mV J sc = 3 7 . 1 mA / c m 2 FF = 7 1 . 7 % E f f = 1 6 . 3 % Wang et al. J. Mater. Chem. C 2017, 5, 1751-1757. Wang et al. Sol. Energy 2014, 108, 308-314. p/ITO contact properties↑ Optical properties↑ Bandgap alignment ↑ Performance improved ↑ JLNU Jilin Normal University Design & fabrication carrier transporting layer 5 MoOx/n-c-Si/BZO (16.6 %) Bifacial metal oxides Back reflector + electron selective layer Wang et al. Nano Energy 2017, 39, 437-443. JLNU Jilin Normal University Design & fabrication carrier transporting layer 6 i-a-Si:H passivation MoOx/n-Si nanowires/Cs2CO3 + ultrathin SiOx (16.9 %) Wang et al. Adv. Funct. Mater. 2018, 1805001 Future prospects … Toward co$t ↓/efficiency ↑ JLNU Jilin Normal University Design & fabrication carrier transporting layer 7 PECVD-free & low temperature Summary 1. Silicon nanowires show great promising owing to their enhanced light- harvesting characteristics 2. The recombination has been effectively reduced by: - TMAH etching - H2 plasma treatment - a-Si:H passivation Further reduce expenditure cost → ultrathin SiOx passivation 3. Dopant-free SiNWs heterojunction solar cells → low temperature/low cost/effective light trapping Eff. 16.9% Wide bandgap √ high work function √ high conductivity √ Dopant-free??? Acknowledgements JLNU Jilin Normal University Gratefully acknowledge the supports from the National Natural Science Foundation of China (Grant Nos. 61475063, 21576111, 61505067, 61605059). Prof. Ying Zhao, Prof. Xiaodan Zhang, Mr. Qianshang Ren, Mr. Rongchi Du Nankai University 8 Thanks for your attention~! 王奉友 功能材料物理与化学教育部重点实验室（吉林师范大 学） wfy@jlnu.edu.cn Xi’an 2018/11/08