Enhanced Grain Size, Photoluminescence, and Photoconversion Efficiency with Cadmium Addition during the Two-Step Growth of CH3NH3PbI3

Suneth C Watthage; Zhaoning Song; Niraj Shrestha; Adam B Phillips; Geethika K Liyanage; Paul J Roland; Randy J Ellingson; Michael J Heben

doi:10.1021/acsami.6b12627

Enhanced Grain Size, Photoluminescence, and Photoconversion Efficiency with Cadmium Addition during the Two-Step Growth of CH₃NH₃PbI₃

ACS Appl Mater Interfaces. 2017 Jan 25;9(3):2334-2341. doi: 10.1021/acsami.6b12627. Epub 2017 Jan 10.

Authors

Suneth C Watthage¹, Zhaoning Song¹, Niraj Shrestha¹, Adam B Phillips¹, Geethika K Liyanage¹, Paul J Roland¹, Randy J Ellingson¹, Michael J Heben¹

Affiliation

¹ Wright Center for Photovoltaics Innovation and Commercialization, School of Solar and Advanced Renewable Energy, Department of Physics and Astronomy, University of Toledo , Toledo, Ohio 43606, United States.

PMID: 28009167
DOI: 10.1021/acsami.6b12627

Abstract

Control over grain size and crystallinity is important for preparation of methylammonium lead iodide (MAPbI₃) solar cells. We explore the effects of using small concentrations of Cd²⁺ and unusually high concentrations of methylammonium iodide during the growth of MAPbI₃ in the two-step solution process. In addition to improved crystallinity and an enhancement in the size of the grains, time-resolved photoluminescence measurements indicated a dramatic increase in the carrier lifetime. As a result, devices constructed with the Cd-modified perovskites showed nearly a factor of 2 improvement in the power conversion efficiency (PCE) relative to similar devices prepared without Cd addition. The grains also showed a higher degree of orientation in the ⟨110⟩ direction, indicating a change in the growth mechanism, and the films were compact and smooth. We propose a Cd-modified film growth mechanism that invokes a critical role for low-dimensional Cd perovskites to explain the experimental observations.

Keywords: cadmium incorporation; carrier lifetime; grain growth; low-dimensional perovskites; nonradiative recombination; perovskite; two-step deposition.