| AVS 62nd International Symposium & Exhibition | |
| Thin Film | Wednesday Sessions |
| Session TF+EN-WeM |
| Session: | ALD for Energy |
| Presenter: | Mariadriana Creatore, Eindhoven University of Technology, The Netherlands |
| Authors: | V. Zardetto, Eindhoven University of Technology, The Netherlands F. di Giacomo, University of Rome "Tor Vergata", Italy G. Lucarelli, University of Rome "Tor Vergata", Italy T.M. Brown, University of Rome "Tor Vergata", Italy A. di Carlo, University of Rome "Tor Vergata", Italy S. Licoccia, University of Rome "Tor Vergata", Italy A. D'Epifanio, University of Rome "Tor Vergata", Italy W.M.M. Kessels, Eindhoven University of Technology, The Netherlands M. Creatore, Eindhoven University of Technology, The Netherlands |
| Correspondent: | Click to Email |
Atomic layer deposition (ALD) offers accurate control in terms of film thickness, chemical and opto-electrical properties. This is extremely appealing for the novel class of mesoscopic solar cells (SCs), where the several interfaces between the absorber, charge transport layers and electrical contacts require the control of selected charge transfer and charge recombination processes.
Organo-metal halide perovskite SCs presently catalyze the interest in the PV community due to the remarkable increase in device performance in the last three years. Recently, thermal ALD processes have been applied for the deposition of TiO2 blocking layers (BLs) in glass- based perovskite SCs[1]. Plasma-assisted ALD allows to extend the process window down to temperatures compatible with conductive plastic substrates. Therefore, in this work we investigate the role of plasma-assisted ALD TiO2 BLs deposited on ITO/PET substrates for a CH3NH3PbI3-xClx perovskite SC. The BLs are required to avoid the charge recombination process at the interface between the transparent conductive oxide layer and the perovskite and/or the hole transport layer. They have been prepared [2] in a remote plasma reactor (FlexALTM) at 150 °C using an heteroleptic alkylamido precursor Ti(CpMe)(NMe2)3 exposure step alternated with an O2 plasma exposure. Very low open circuit voltage (VOC = 50mV) and efficiency (η = 0.01%) have been measured in the absence of the blocking layer. In this case, the analysis of dark current-voltage measurements revealed the lack of diode-like behavior and a significant exchange current (7 mA∙cm-2). The introduction of thin TiO2 layers brought to an increment in all the photovoltaic parameters (JSC, VOC and FF), with a saturation in electrical efficiency for a TiO2 thickness above 5.5 nm. The saturation in the anodic branch of the JV curve (V> 0) for ALD layers thicker than 5.5 nm points out that at this thickness the ALD layer is compact and therefore it suppresses the charge recombination processes. Dark current-voltage measurements have highlighted the decrease of exchange current and dark reverse current (V<0) up to three orders of magnitude with respect to the device without BL. The maximum performance of 9.2% on ITO-PET and 12.9% on ITO-Glass was achieved with 11 nm- thick TiO2 BL, overcoming the efficiency achieved with conventional sol gel- deposited TiO2 BLs (respectively, 4% and 8% on the two substrates).
[1] M. Grätzel, Nature Materials, 13, 838–842 (2014).
[2] F. Di Giacomo and V. Zardetto et al, Adv. Energy. Mater. 1401808 (2015)