Air stability of TiO2/PbS colloidal nanoparticle solar cells and its impact on power efficiency

Abstract

The short-term (less than 1 hour) exposure of TiO2/PbS quantum dot photovoltaics to air increases the open circuit voltage (Voc) and fill factor (FF) while slightly decreasing the short circuit current density (Jsc), leading to a power conversion efficiency above 4% and a peak external quantum efficiency over 80% for 1.1 eV PbS. The resulting Jsc, Voc, and FF under 100 mW/cm2 AM1.5 are 18.6 mA/cm2, 0.517 V, and 42% for 1.1 eV PbS and 8.03 mA/cm2, 0.655 V, and 35% for 1.7 eV PbS, respectively. Long-term air exposures result in much lower conductivities. Furthermore, short-term air exposure effects are fully reversible upon removal from air, and longer-term effects are mostly reversible through soaking in 1,2-ethanedithiol.

Atomic layer deposition of zinc sulfide with Zn(TMHD)2

“…Solar cell devices were a) Electronic mail: galers@ucsc.edu made using the method described elsewhere. 11 Quartz substrates with patterned ITO were used with $100 nm of solgel deposited TiO 2 and $200 nm of 30 nm TiO 2 nanoparticles as the n type contact layer. A 2.5 nm layer of ALD ZnS was then deposited on top of the porous TiO 2 as a buffer layer.…”

“…A 2.5 nm layer of ALD ZnS was then deposited on top of the porous TiO 2 as a buffer layer. A 945 nm layer of PbS quantum dots was deposited using a ligand exchange method described elsewhere, 11 and finally a gold contact was deposited by evaporation. These devices were used to observe the effect of the ZnS as a buffer layer in a solar cell.…”

Pulsed Laser Ablation Based Synthesis of PbS‐Quantum Dots‐Decorated One‐Dimensional Nanostructures and Their Direct Integration into Highly Efficient Nanohybrid Heterojunction‐Based Solar Cells

“…Indeed, Figure shows that, regardless of the TiO 2 ‐NR's length, the relative variation of the PCE of our devices follows the same trend; that is a slight relative decrease of ≈15% after 6 months and ≈27% after 14 months of their on‐shelf storage in ambient air with no specific encapsulation. This highlights the excellent stability of the laser synthesized PbS‐QDs based PV devices when compared to that of similar devices using chemically‐synthesized PbS‐QDs, of which PCE generally undergoes drastic and rapid relative decrease (from ≈20% to more than 70% in the few days following their fabrication if no encapsulation is used and/or caution is taken to prevent the rapid oxidation of the PbS‐QDs …”

Towards understanding the initial performance improvement of PbS quantum dot solar cells upon short-term air exposure

“…Thereinto, all parameters of the PbS-TBAI devices gradually increase with air exposure time, while the PbS-EDT devices quickly degrade aer air exposure, which is the same as our previous results. 17 Actually, as pointed out previously, 18 the PbS-TBAI devices usually need longer air-exposure time to reach their highest efficiency. Obviously, the PbS-TBAI/PbS-EDT devices behave very similarly to the PbS-TBAI devices rather than the PbS-EDT devices, implying that the PbS-TBAI lm might play a dominant role in their performance change in comparison with the PbS-EDT layer due to the former's much higher thickness (200 nm as opposed to 40 nm for the PbS-EDT layer).…”