Electron Spin Resonance Investigations on Perovskite Solar Cell Materials Deposited on Glass Substrate
- PDF / 1,027,603 Bytes
- 6 Pages / 432 x 648 pts Page_size
- 81 Downloads / 191 Views
MRS Advances © 2018 Materials Research Society DOI: 10.1557/adv.2018.171
Electron Spin Resonance Investigations on Perovskite Solar Cell Materials Deposited on Glass Substrate C. L. Saiz1, E. Castro2, L. M. Martinez1, S. R. J. Hennadige2, L. Echegoyen2, S. R. Singamaneni1 1
Department of Physics, The University of Texas at El Paso, El Paso, Texas 79968, USA.
2
Department of Chemistry, The University of Texas at El Paso, El Paso, Texas 79968, USA.
ABSRTACT
In this article, we report low-temperature electron spin resonance (ESR) investigations carried out on solution processed three-layer inverted solar cell structures: PC61BM/CH3NH3PbI3/PEDOT:PSS/Glass, where PC61BM and PEDOT:PSS act as electron and hole transport layers, respectively. ESR measurements were conducted on ex-situ light (1 Sun) illuminated samples. We find two distinct ESR spectra. First ESR spectra resembles a typical powder pattern, associated with gx = gy = 4.2; gz = 9.2, found to be originated from Fe3+ extrinsic impurity located in the glass substrate. Second ESR spectra contains a broad (peak-to-peak line width ~ 10 G) and intense ESR signal appearing at g = 2.008; and a weak, partly overlapped, but much narrower (peak-to-peak line width ~ 4 G) ESR signal at g = 2.0022. Both sets of ESR spectra degrade in intensity upon light illumination. The latter two signals were found to stem from light-induced silicon dangling bonds and oxygen vacancies, respectively. Our controlled measurements confirm that these centers were generated during UV-ozone treatment of the glass substrate –a necessary step to be performed before PEDOT:PSS is spin coated. This work forms a significant step in understanding the lightinduced- as well as extrinsic defects in perovskite solar cell materials.
INTRODUCTION Polycrystalline thin films of CH3NH3PbI3 (MAPbI3), being the dominant form of photovoltaic applications, have drawn a great deal of scientific and technological interest due to a boost in performance from 3.8% in 2005 to a record high 22.1% power conversion efficiency in 2015, exceptional electron-hole diffusion length (>1 µm), and high open circuit voltage of >1 V [1]. Most importantly, these materials are cheap to fabricate using simple low temperature solution-based methods, and employ 1000-times less light harvesting material compared to the current market leader, polycrystalline silicon, with efficiency > 25%. Despite these extraordinary properties, under normal solar operating conditions in open air, MAPbI 3 turns into a photo-inactive yellow phase and can no longer be used for photovoltaic applications. Due to defect formation and ion migration, MAPbI3
Downloaded from https://www.cambridge.org/core. Access paid by the UCSB Libraries, on 19 Feb 2018 at 09:48:52, subject to the Cambridge Core terms of use, available at https://www.cambridge.org/core/terms. https://doi.org/10.1557/adv.2018.171
degrades relatively rapidly and becomes highly unstable [2]. In addition, MAPbI3-based materials are vulnerable to degradation by external stimuli such as prolon
Data Loading...
