Performance Enhancement of PbS Quantum Dot-Sensitized Solar Cells with CH3NH3PbI3-Thin Capping Layer
Gabseok Seo a b, Tae Kyu Ahn a b, Sang Il Seok a b, Seungchan Ryu b, Jangwon Seo b
a Sungkyunkwan University, South Korea, 300 Cheoncheon-dong, Jangan-gu, Suwon, 440, Korea, Republic of
b Korea Research Institute of Chemical Technology (KRICT), 141 Gajeongro, Yuseong, Daejeon, 305, Korea, Republic of
International Conference on Hybrid and Organic Photovoltaics
Proceedings of 6th International Conference on Hybrid and Organic Photovoltaics (HOPV14)
Ecublens, Switzerland, 2014 May 11th - 14th
Organizers: Michael Graetzel and Mohammad Nazeeruddin
Poster, Gabseok Seo, 321
Publication date: 1st March 2014

Semiconductor quantum dots (QDs) have received great attention as a solar energy material due to a high extinction coefficient, tunable band gap, easy production, large dipole moment and multiple exciton generation (MEG) effect. Among them, PbS is one of most explored materials in QD solar cells because of a broad light harvesting from the visible to the infrared (IR) range by easily adjusting QD sizes. Recently, it was reported that lead halide perovskite materials (CH3NH3PbX3, X=Cl, Br, I) possess a high carrier mobility and long carrier diffusion length.

 Herein, we report highly improved performance of PbS quantum dot-sensitized solar cells by capping PbS QDs on top of nanostructured TiO2 electrode with thin CH3NH3PbI3 layer. The successive ionic layer adsorption and reaction (SILAR) application of a PbI2 and Na2S solution on mesoporous TiO2 electrode by repeating spin-coating and the subsequent dipping into CH3NH3I solution in a final stage enabled the formation of CH3NH3PbI3-capped PbS QDs. Then, hole transporting polymers (P3HT and PEDOT:PSS) were also spin-coated and an Au counter electrode was deposited by thermal evaporation to complete the device. The resulting device showed a large enhancement in Jsc with improved stability, as compared to the device without CH3NH3PbI3 capping layer, reaching overall efficiency to 3.2% under simulated solar illumination (AM1.5, 100 mW·cm-2). (See Figure as below) The impedance spectroscopy and the time-resolved PL decay measurement before and after capping PbS QDs with CH3NH3PbI3 layer show that the great improvement of Jsc may be due to both a reduced charge recombination and a better charge extraction. Therefore, our approach will provide a new guideline for developing high performing solar cells.


Solar cell performance of PbS quantum dots and enclosed in situ with Perovskite thin layer
(1) Julian Burschka, Norman Pellet, Soo-Jin Moon, Robin, Hymphry-Baker, Peng Gao, Mohammad K. Nazeeruddin , Michael Gratzel. Sequential deposition as a route to high-performance perovskite-sensitized solar cells. Nature. 2013, 499, 316-319 (2) Sang Hyuk Im, Hi-Jung Kim, Sungwoo Kim, Sang-Wook Kim, Sang Il Seok. Organic Electronics 2012, 13, 2352-2357 (3) Jin Hyuk Heo, Sang Hyuk Im, Jun Hong Noh, Tarak N. Mandal, Choong-Sun Lim, Jeong Ah Chang, Yong Hui Lee, Hi-Jung Kim, Arpita Sarkar, Md. K. Nazeeruddin, Michael Gratzel, Sang Il Seok, Nature Photonics 2013, 7, 486,491
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