title: Growth of CH3NH3PbI3 cuboids with controlled size for high-efficiency perovskite solar cells.
abstract: Perovskite solar cells with submicrometre-thick CH(3)NH(3)PbI(3) or CH(3)NH(3)PbI(3-x)Cl(x) active layers show a power conversion efficiency as high as 15%. However, compared to the best-performing device, the average efficiency was as low as 12%, with a large standard deviation (s.d.). Here, we report perovskite solar cells with an average efficiency exceeding 16% and best efficiency of 17%. This was enabled by the growth of CH(3)NH(3)PbI(3) cuboids with a controlled size via a two-step spin-coating procedure. Spin-coating of a solution of CH(3)NH(3)I with different concentrations follows the spin-coating of PbI(2), and the cuboid size of CH(3)NH(3)PbI(3) is found to strongly depend on the concentration of CH(3)NH(3)I. Light-harvesting efficiency and charge-carrier extraction are significantly affected by the cuboid size. Under simulated one-sun illumination, average efficiencies of 16.4% (s.d. ± 0.35), 16.3% (s.d. ± 0.44) and 13.5% (s.d. ± 0.34) are obtained from solutions of CH(3)NH(3)I with concentrations of 0.038 M, 0.050 M and 0.063 M, respectively. By controlling the size of the cuboids of CH(3)NH(3)PbI(3) during their growth, we achieved the best efficiency of 17.01% with a photocurrent density of 21.64 mA cm(-2), open-circuit photovoltage of 1.056 V and fill factor of 0.741.
authors.affiliation: School of Chemical Engineering and Department of Energy Science, Sungkyunkwan University, Suwon 440-746, Korea.
authors.forename: Jeong-Hyeok
authors.initials: JH
authors.lastname: Im
authors.affiliation: School of Chemical Engineering and Department of Energy Science, Sungkyunkwan University, Suwon 440-746, Korea.
authors.forename: In-Hyuk
authors.initials: IH
authors.lastname: Jang
authors.affiliation: 1] Laboratory for Photonics and Interfaces, Institute of Chemical Sciences and Engineering, School of Basic Sciences, Ecole Polytechnique Fédérale de Lausanne, CH-1015 Lausanne, Switzerland [2] Max-Planck-Institute for Solid-State Research, Heisenbergstrasse 1, 70569 Stuttgart, Germany.
authors.forename: Norman
authors.initials: N
authors.lastname: Pellet
authors.affiliation: Laboratory for Photonics and Interfaces, Institute of Chemical Sciences and Engineering, School of Basic Sciences, Ecole Polytechnique Fédérale de Lausanne, CH-1015 Lausanne, Switzerland.
authors.forename: Michael
authors.initials: M
authors.lastname: Grätzel
authors.affiliation: School of Chemical Engineering and Department of Energy Science, Sungkyunkwan University, Suwon 440-746, Korea.
authors.forename: Nam-Gyu
authors.initials: NG
authors.lastname: Park