In the case of Inverted Hybrid Perovskite (PVSKs) best PCE of 20.45 % achieved by using a triple cation perovskite formulation, while more reliable nitrobenzene additive based methylammonium-free (CsFA) PVSK formulation provide an increased mean PCE from 15.34% to 17.09%, with a much narrower PCE standard deviation distribution (please see figure 1). The improved performance is attributed to the interaction of perovskite’s colloidal particles with nitrobenzene, as well as passivation of grain boundary defects (A. Ioakeimidis & S. A. Choulis, Materials, 2020). A range of solution processed metal oxides suitable for carrier selective contacts such as the solution combustion synthesized (SCS) un-doped and doped NiCo2O4 (I.T. Papadas, et al, Advanced Science, 2018, and A. Ioakeimidis, et al., APL Materials, 2019), dellaffosite CuGaO2 (I. Papadas, et al, Materials Today Energy, 2018) and the binary CuAlO2/Cu-O (A Savva, et al, ACS Appl. Energ. Mat, 2019) developed and their application for high performance PVSKs was demonstrated. The β-alanine surface treatment process on SCS based carrier selective contacts eliminated major PVSK degradation mechanisms, providing, J/V hysteresis-free, efficient, and thermally stable PVSKs. Based on this development (β-alanine surface treated HTLs) we have achieved as shown in figure 2 greatly improved (from 24 h for the un-treated inverted PVSCs to 1000 h for the β-alanine-surface treated Cu:NiOx HTL based inverted PVSKs) thermal device stability (F. Galatopoulos, et al., Submitted to Nanomaterials, 2020). Furthermore, the addition of the nitrobenzene within the reliable methylammonium-free (CsFA) perovskite formulation increased humidity lifetime performance (75% RH and 22 °C) by 10 times due to defect passivation and inhibition of moisture permeation (A. Ioakeimidis and S. Choulis, Materials, 2020).
In the case of Inverted OPVs, by using non-fullerene acceptors inverted OPVs with PCE of 13.85 % have been achieved but lifetime limitations have been identified. Sol-Pro trials to replace the commonly used thermally evaporated MoO3 HTL with a high-performance/stable solution processed metal-oxide HTL for inverted OPVs did not produce reliable devices. In the case of inverted OPVs the best performing solution processed, hole selective contact remains the PEDOT:PSS combined with Dynol/Zonyl additives (F. Hermerschmidt, et al, ACS Appl. Mater. and Interf., 2017). As shown in figure 3, the Sol-Pro project developed a high-performance low temperature solution processed electron selective contact consisting of 10 at% antimony doped tin oxide (ATO) and the neutral polymer polyethylenimine (PEI) for high performance inverted OPVs (E. Georgiou, et al., APL Materials 2019). Furthermore, low cost solution ITO-free OPVs were developed consisting of Ag NWs and doped metal oxide-based carrier selective contact (E. Georgiou, et al, Manuscript under preparation, 2020). As indicated within the Sol-Pro action important Sol-Pro developments on PVs were also applied to close related applications such as organic light emitting diodes (OLEDs). We have shown that metal oxide (MO) interfacial layers inserted between ITO and PEDOT:PSS can be used to improve the bottom OLEDs electrodes. Best performance was achieved using the Sol-Pro SCS developed co-doped NiCo2O4, for which the current efficiency and luminous efficacy of SY OLEDs increased, respectively, by 12% and 11% (S. M. Pozov, et al., Submitted to Organic Electronics, June-2020).
In the case of all-oxides solution processed PVs. A method to assemble networks of strongly connected metal oxide nanoparticles was performed by short ligand and a polar aprotic solvent for the colloidal dispersion of SCS-based MnFe2O4 (MFO) NPs. Figure 4 shows characterisation studies for relevant PV properties of the MnFe2O4 nanoparticles and thin films. The proposed strategy is crucial to obtain functional all oxides photovoltaic devices that are fabricated by solution processing. All solution processed inorganic MnFe2O4 based heterojunction photovoltaics were fabricated. The corresponding all-oxides solar cells reveal a high open circuit voltage of 1.17 V with a fill factor of 51.2 % but a limited short circuit current of 0.07 mA cm-2, delivering PCE of 4.2 10-2 % under 100 mW cm-2 illumination. Despite the low PCE values of the novel SCS based all inorganic PVs, the obtained Voc values are much higher compared to Voc values of all-oxide solution processed based PVs reported in the literature such as [BiFeO3 (∼0.41 V)] and [Pb(ZrTi)O3 (~0.6 V)] (I. T. Papadas, et al., Manuscript under preparation, 2020).
