Shuanghong Chen

Mesoporous SnO2 nanoparticle films as electron-transporting material in perovskite solar cells

Perovskite solar cells with mesoporous metal oxide films as scaffold layers have demonstrated very impressive advances in performance recently. Here, we present an investigation into mesoporous perovskite solar cells incorporating mesoporous SnO2 nanoparticle films as electron-transporting materials and scaffold layers, to replace traditional mesoporous TiO2 films. We have optimized the SnO2 film thickness and treated the surface of the SnO2 film with an aqueous solution of TiCl4. Due to the TiCl4 treatment the recombination process was significantly retarded. The short-circuit current density (Jsc) and open-circuit voltage (Voc) reached nearly 18 mA cm−2 and 1 V, respectively. Consequently, the power conversion efficiency of the device with the SnO2 film exceeded 10%.

TiO2 Sub-microsphere Film as Scaffold Layer for Efficient Perovskite Solar Cells.

TiO2 sub-microspheres composed of anatase granular-like nanocrystallines with an average diameter ∼250 nm are synthesized using sol-gel method and employed as the scaffold layer for efficient mesocopic perovskite solar cells. Compared with mesoporous TiO2 films composed of ∼18 nm nanoparticles, the sub-microsphere films show superior light-trapping characteristics and significantly improve the light-harvesting capability of the solar cells. In addition, the charge-transport performance is also dramatically improved according to the transient photocurrent decay despite there being no significant difference in the perovskite layer surface morphology. As a result, an average power conversion efficiency of 15% with a highly uniform distribution is achieved for the solar cells with TiO2 sub-microsphere films, 12% higher than those with TiO2 nanoparticle films. The combination of light-harvesting capability and fast charge transfer make the TiO2 sub-microsphere film a good candidate as the scaffold layer for efficient perovskite solar cells.

Ligand-free nano-grain Cu2SnS3 as a potential cathode alternative for both cobalt and iodine redox electrolyte dye-sensitized solar cells

Tetragonal phase Cu2SnS3 (CTS) in the form of nano-grain thin film serves as an efficient inexpensive electrocatalyst alternative to the commonly used Pt in dye-sensitized solar cells (DSSCs) exhibiting remarkable electrochemical stability and electrocatalytic activity for both cobalt (Co(III)/Co(II))- and iodine (I3−/I−)-based redox electrolytes. In this study, the catalytic activity of the CTS electrode was first theoretically predicted via first-principles calculations using density functional theory. Electrochemical measurements confirm their superior catalytic performance to Pt toward both the reduction of I3− and Co3+. Significantly, ensuing DSSCs with the CTS cathode demonstrate a photovoltaic efficiency of 10.26%, higher than that with Pt (9.31%). Through impedance spectra, we also show that increasing the amount of CTS loading can further enhance its apparent catalytic performance. However, improving the crystallization of the CTS film by increasing the annealing temperature to a certain degree will only reduce its activity.

Promoting perovskite crystal growth to achieve highly efficient and stable solar cells by introducing acetamide as an additive

To date, perovskite solar cells (PSCs) have achieved superior photovoltaic performance with a high power conversion efficiency (PCE) of over 22%. However, there are very few devices which have a high PCE and high stability simultaneously. In this study, we fabricated PSCs made from (FAPbI3)0.85(MAPbBr3)0.15 using the non-volatile Lewis base acetamide (CH3CONH2) as an additive. Compared to a reference device, the device containing 5xa0mg mL−1 CH3CONH2 displayed a markedly improved PCE of 19.01% and less hysteresis, due to its high-quality film with a better crystal structure, evidently larger grain size and greater thickness. In addition, the device with CH3CONH2 exhibited better humidity and heat stability. The unsealed device could maintain about 70% and 50% of its starting PCE under around 50% and 80% relative humidity (RH) for 1000 h and 700 h, respectively. Meanwhile, the unsealed device with CH3CONH2 could retain about 80% and 60% of its starting PCE at 60 °C and 85 °C for 200 h and 150 h, respectively. These results clearly show that using CH3CONH2 as an additive can promote crystal growth and enhance the grain size of perovskite thin films and introducing a suitable additive can realize the simultaneous improvement of the PCE and stability of PSCs.

Semiconductor Sensitized Solar Cells Based on BiVO4-Sensitized Mesoporous SnO2 Photoanodes.

Low cost, stable and visible-light-responsive bismuth vanadate (BiVO4) was used as the light absorbing material to fabricate a low bandgap oxide solar cell on mesoporous SnO2 photoanode. BiVO4 nanoparticles were grown on the mesoporous SnO2 films employing successive ionic layer adsorption and reaction process. The optimized BiVO4 solar cell shows an incident photon to current conversion efficiency of more than 60% at a wide range of visible region (350 nm-450 nm), leading to a power conversion efficiency of 0.56% at AM1.5, 100 mW x cm(-2). This result provides important insights into the low cost and robust oxide solar cells.