Mesoscopic TiO₂/Nb₂O₅ Electron Transfer Layer for Efficient and Stable Perovskite Solar Cells

Abstract

However, the major hurdles in commercialization of PSCs are their low long-term stability and hysteretic behavior in current-voltage (J-V) characteristics that need to be resolved. [11] To date, various mechanisms are proposed for the hysteretic behavior of PSCs including charge trapping -detrapping, [12] ferroelectricity, [13] ion migration [14] or interfacial capacitance. [15] The typical solar cell consists of transparent conductive electrode (fluorinedoped tin oxide (FTO)/indium tin oxide (ITO))/electron transport layer (ETL)/ perovskite absorber layer/hole transporting layer (HTL)/metal electrode. [16] For efficient PSCs, the ETL should exhibit i) high electron mobility to ensure fast electron transport within ETL, ii) proper energy level alignment for effective electron transfer and hole blocking, iii) high stability, iv) high transmittance, and v) easy processability. [17,18] Generally, TiO 2 has been widely used as an ETL in PSCs, however, the TiO 2 /perovskite interface suffers from charge accumulation owing to inefficient charge transfer. [19][20][21] Many strategies have been employed to circumvent this issue and improve the performance of the PSC. [22][23][24][25] For example, doping of compact TiO 2 ETL with inorganic Y, Zr, and Mg metal cations yields in reduced hysteresis because of possible defect passivation. [26][27][28] Moreover, surface passivation of mesoporous TiO 2 (ms-TiO 2 ) with various metal oxides There has been tremendous advancement in the field of perovskite photovoltaics by means of interfacial engineering, compositional engineering and optimization of charge collection efficiency. The large bandgap oxides deposited using atomic layer deposition (ALD) technique have proven to be successfully passivating the interfacial defects owing to the advantages offered by this technique. Here, the effect of surface modification of mesoporous TiO 2 (ms-TiO 2 ) layer with a transition metal oxide named niobium pentoxide (Nb 2 O 5 ) deposited by ALD technique on the performance and stability of perovskite solar cells (PSCs) is investigated. The results reveal that functionalization with ultrathin Nb 2 O 5 layer improve the optoelectronic properties and morphology of the deposited perovskite films. Moreover, the charge transfer is improved and hence the interfacial recombination is reduced. This results in improved power conversion efficiency (PCE) from 19.11% to 21.04% and opencircuit voltage (V OC ) from 1.118 to 1.147 V for the modified champion device. Additionally, the device shows negligible hysteresis with enhanced shelf life thermal and UV stabilities.

The high open-circuit voltage of perovskite solar cells: a review

“…As an example, Hong and co-workers modified the surface of mesoporous-TiO 2 with a Nb 2 O 5 layer deposited by the atomic layer deposition technique. 91 They found that the ultrathin Nb 2 O 5 layer improved the optoelectronic properties and morphology of the deposited perovskite films, enhanced the charge transfer, and suppressed the recombination at the interface. As a result, solar cells using Cs 0.1 FA 0.9 PbI 3 as the light absorber showed a higher V OC of 1.147 V and PCE of 21.04%, compared with 1.118 V and 19.11%, respectively, for the bare TiO 2 based device.…”

Metal oxide charge transporting layers for stable high-performance perovskite solar cells

“…3e). 51 After adding this ultrathin Nb 2 O 5 layer (shown in the transmission electron microscopy (TEM) image in Fig. 3d), the morphology of the deposited perovskite layer on the modified mesoporous TiO 2 ETL promoted charge transfer in the PSC with better performance (Fig.…”

Recent Progress of Light Intensity‐Modulated Small Perturbation Techniques in Perovskite Solar Cells

“…[1,2] These advancements are because of the development in the device engineering, designing, and understanding of the physical processes occurring within the PSCs. [3][4][5][6] Despite this, there are some fundamental processes for which a complete and unambiguous understanding needs to be The small perturbation frequency-resolved techniques have been powerful tools in unraveling the kinetic processes governing the operation of perovskite solar cells (PSCs). One such technique is electrochemical impedance spectroscopy (EIS).…”

“…[ 1,2 ] These advancements are because of the development in the device engineering, designing, and understanding of the physical processes occurring within the PSCs. [ 3–6 ] Despite this, there are some fundamental processes for which a complete and unambiguous understanding needs to be established and translated to the real‐world conditions. One of the reasons that impart complexity to the PSCs is the interaction of ionic and electronic charge carriers.…”