BEGIN:VCALENDAR
VERSION:2.0
PRODID:Icfo
X-PUBLISHED-TTL:P1W
BEGIN:VEVENT
UID:69d25646271bc
DTSTART:20230223T090000Z
SEQUENCE:0
TRANSP:OPAQUE
LOCATION:ICFO Auditorium and Online (Teams)
SUMMARY:ICFO | YONGJIE WANG
CLASS:PUBLIC
DESCRIPTION:Climate change and global energy demand urge the development of
  renewable energy sources for worldwide power supply. Photovoltaic devices
  that convert solar energy directly into electricity are the most promisin
 g\, if not the only\, technique to meet the requirements. Solution-process
 ed solar cells are especially attractive due to their lightweight\, low co
 st\, and large-area mass manufacturing features.\nAmong solution-processed
  materials\, nanocrystals are one of the most promising\, thanks to their 
 material-property tunabilities\, such as size\, morphology\, composition\,
  electronic and optical properties\, just to name a few. In the last decad
 e\, nanocrystal solar cells are mainly based on lead chalcogenide nanocrys
 tals\, although they face problems related to the toxicity of the element 
 lead. Silver-bismuth sulfide nanocrystals are excellent substitutes for le
 ad chalcogenides\, thanks to their adequate bandgaps and extraordinarily h
 igh absorption coefficients. However\, the energy conversion efficiency ha
 s lagged behind their toxic counterparts\, mainly due to limited charge-ca
 rrier diffusion length and uncontrolled cation-disorder.\nIn this thesis\,
  we pinpoint the detrimental effects of cation inhomogeneity in ternary si
 lver bismuth sulfide nanocrystals and further homogenize the cation-disord
 er by a facile post-annealing process\, leading to absorption coefficients
  higher than any other commonly used solar materials over a wide range of 
 400 - 1000 nm. The cation-disorder configuration transition was further co
 nfirmed by the combination of ab initio density functional theory calculat
 ion and experimental material characterizations.\nFurther optical modellin
 g suggested a 30nm absorber layer possesses the potential for high Jsc up 
 to 30 mA/cm2 and efficiency up to 26%. In addition to optical absorption e
 nhancements\, we also found elongated diffusion length up annealing\, poin
 ting to an anticipated high performance with ultrathin absorber. Ultrathin
  solar cells were thus fabricated with specially designed architecture and
  we achieved a record efficiency up to 9.17%\, independently certified as 
 8.85% by Newport. The ultrathin solar cells also showed excellent stabilit
 y under ambient conditions.\nIn order to comply with mass manufacturing pr
 ocesses\, we developed a solution-phase ligand-exchange procedure based on
  aqueous nanocrystal inks that enable single-step deposition of the active
  layer\, reducing drastically the number of processing steps. Solar cell d
 evices were built with the nanocrystal inks based on single-step depositio
 n process and they showed a promising efficiency up to 7.3%\, much higher 
 than previous ink device record.\nIn sum\, we have achieved record-high pe
 rformance\, exceptionally stable AgBiS2 nanocrystal solar cells with both 
 solid-state and solution-phase ligand-exchange procedures. This work sets 
 a landmark for the development of environmentally friendly\, low-temperatu
 re\, solution-processed inorganic solar cells and opens a new field of eng
 ineering the atomic configuration of semiconductors as a means to achieve 
 extraordinary optoelectronic properties.\n&nbsp\;\nThesis Director: Prof D
 r. Gerasimos Konstantatos
DTSTAMP:20260405T123206Z
END:VEVENT
END:VCALENDAR