Special Seminar by Prof. Wong (Georgia Tech)

Prof. C.P. Wong from the School of Materials Science and Engineering, Georgia Institute of Technology will talk at a special seminar at TU Delft (EEMCS), 8 October 2018.
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Special Seminar by prof.dr. C.P. Wong

Materials Engineering for Stability Improvement of Perovskite Solar Cells 
Monday October 8th, 10.00 - 10.45 hours.


Prof.dr. C.P. Wong

Microelectronic and Photonic Packaging Materials Group, School of Materials Science and Engineering, Georgia Institute of Technology

Biography and abstract (Pdf file)

Prof. C.P. Wong is the international expert involved in the research project 'Super Conducting Carbon Nanotubes' within the 4TU.HTM research programme 'New Horizons in Designer Materials'.

Abstract

Organolead halide perovskites have recently emerged as a fascinating light harvesting material that combines the advantages of simple fabrication process and excellent electronic properties. The power conversion efficiency (PCE) of perovskite solar cells (PSCs) has been rapidly improved from 3.8% to 23.3% within the past several years. In contrast to the stunning rise in efficiency, the instability of the PSCs is its Achilles’ heel. The instability issue of the whole device originates not only from the perovskite layer itself, but also from the use of doped organic charge transport materials, such as spiro-MeOTAD. This talk is to provide material strategies to improve the stability of the organolead halide perovskite materials as well as other functional layers in PSCs. To improve the air-stability of perovskite films prepared from two-step sequential deposition by simultaneously eliminating PbI2 residue and improving the crystallinity of the perovskite films. We developed PbI2 thin films with nano-pores and tunable crystal sizes, which enabled full conversion of PbI2 to MAPbI3. A large perovskite crystalline domains, and that the impurity-free, lead to reduced trap states and improved air-stability of the perovskite thin films. The second part of my talk is devoted to improve the stability of the entire PSC device by developing a solution-processed NiOx hole-transport layer, as the hygroscopic nature of the NiOx film suppresses the diffusion of water molecules to the perovskite, and it is also insusceptible to heat. As a result, the PSCs with a structure of FTO / TiO2 / Perovskite / NiOx / Au demonstrated remarkable air-stability and thermal stability. By further modifying of the NiOx / metal interface by CuSCN, we further realized high-efficiency PSCs with excellent air stability, exhibiting nearly no efficiency degradation after exposed to air for 4 months. Furthermore, the ion migration-induced instability issue through incorporating extrinsic alkali cations (i.e., Rb+, K+, Na+, or Li+) into the perovskite. The size-dependent interstitial occupancy of the extrinsic alkali cations in the perovskite lattice was proposed and verified for the first time through density functional theory (DFT) calculations. Such interstitial doping method suppressed I- ion migration in the bulk of perovskites, thus resulting in reduced I-V hysteresis of the PSCs, weakened poling effects and improved photo stability of wide-bandgap mixed-halide perovskites.


Information

Time: Monday 8th of October, 10:00 - 10:45 hours
Place: TU Delft, EEMCS, Feldmannweg 17, 2628 CT Delft
Room: EKL Colloquium room (EKL 01.180)

For more information, please contact dr. Amir Mirza Gheytaghi.

Special Seminar by Prof. Wong (Georgia Tech)

Special Seminar by prof.dr. C.P. Wong

Materials Engineering for Stability Improvement of Perovskite Solar Cells 
Monday October 8th, 10.00 - 10.45 hours.


Prof.dr. C.P. Wong

Microelectronic and Photonic Packaging Materials Group, School of Materials Science and Engineering, Georgia Institute of Technology

Biography and abstract (Pdf file)

Prof. C.P. Wong is the international expert involved in the research project 'Super Conducting Carbon Nanotubes' within the 4TU.HTM research programme 'New Horizons in Designer Materials'.

Abstract

Organolead halide perovskites have recently emerged as a fascinating light harvesting material that combines the advantages of simple fabrication process and excellent electronic properties. The power conversion efficiency (PCE) of perovskite solar cells (PSCs) has been rapidly improved from 3.8% to 23.3% within the past several years. In contrast to the stunning rise in efficiency, the instability of the PSCs is its Achilles’ heel. The instability issue of the whole device originates not only from the perovskite layer itself, but also from the use of doped organic charge transport materials, such as spiro-MeOTAD. This talk is to provide material strategies to improve the stability of the organolead halide perovskite materials as well as other functional layers in PSCs. To improve the air-stability of perovskite films prepared from two-step sequential deposition by simultaneously eliminating PbI2 residue and improving the crystallinity of the perovskite films. We developed PbI2 thin films with nano-pores and tunable crystal sizes, which enabled full conversion of PbI2 to MAPbI3. A large perovskite crystalline domains, and that the impurity-free, lead to reduced trap states and improved air-stability of the perovskite thin films. The second part of my talk is devoted to improve the stability of the entire PSC device by developing a solution-processed NiOx hole-transport layer, as the hygroscopic nature of the NiOx film suppresses the diffusion of water molecules to the perovskite, and it is also insusceptible to heat. As a result, the PSCs with a structure of FTO / TiO2 / Perovskite / NiOx / Au demonstrated remarkable air-stability and thermal stability. By further modifying of the NiOx / metal interface by CuSCN, we further realized high-efficiency PSCs with excellent air stability, exhibiting nearly no efficiency degradation after exposed to air for 4 months. Furthermore, the ion migration-induced instability issue through incorporating extrinsic alkali cations (i.e., Rb+, K+, Na+, or Li+) into the perovskite. The size-dependent interstitial occupancy of the extrinsic alkali cations in the perovskite lattice was proposed and verified for the first time through density functional theory (DFT) calculations. Such interstitial doping method suppressed I- ion migration in the bulk of perovskites, thus resulting in reduced I-V hysteresis of the PSCs, weakened poling effects and improved photo stability of wide-bandgap mixed-halide perovskites.


Information

Time: Monday 8th of October, 10:00 - 10:45 hours
Place: TU Delft, EEMCS, Feldmannweg 17, 2628 CT Delft
Room: EKL Colloquium room (EKL 01.180)

For more information, please contact dr. Amir Mirza Gheytaghi.