Abstract
Highly efficient all-inorganic perovskite solar cells require a fast charge transfer from CsPbBr3 to TiO2 to reduce the recombination from trap states. Herein, we insert a CdS/CdSe/CdS quantum dot (QD) layer between the TiO2 and CsPbBr3 layers to fabricate all-inorganic perovskite solar cells. By tuning the thicknesses of the CdSe layer of CdS/CdSe/CdS QDs, the conduction band (CB) levels can be adjusted to -3.72~-3.87 eV. After inserting the QD intermediate layer, the energy offset between the CB of TiO2 and CsPbBr3 is reduced, thus leading to a charge transfer rate boost from 0.040×109 to 0.059×109 s−1. The power conversion efficiency (PCE) of the solar cell with QD intermediate layer achieves 8.64%, which is 20% higher than its counterpart without QDs.
Highlights
Hybrid organic-inorganic lead halide perovskite solar cells (PSCs) are promising candidates for commercialization, owing to their extremely high power conversion efficiency (PCE over 22%) and low fabrication cost
Arising from the improved charge transfer rate, the optimized device exhibits a PCE of 8.64%, which is 20% higher than the device without quantum dot (QD) intermediate layer
The pristine CsPbBr3 PSC delivers a moderate PCE of 7.15% (Voc = 1:368 V, Jsc = 6:69 mA cm−2, and FF = 0:78), which is comparable to other hole transport layer (HTL)-free inorganic PSCs [8, 15]
Summary
Hybrid organic-inorganic lead halide perovskite solar cells (PSCs) are promising candidates for commercialization, owing to their extremely high power conversion efficiency (PCE over 22%) and low fabrication cost. Hodes et al first used CsPbBr3 as the light absorber with a typical device structure of FTO/c-TiO2/m-TiO2/CsPbBr3/HTM/Au, achieving a PCE of 5.95% and an open-circuit voltage (Voc) of 1.28 V [11] These parameters are comparable to those MA-containing hybrid PSCs. Later, Liu and his coworkers fabricated an all-inorganic PSC with architecture of FTO/cTiO2/m-TiO2/CsPbBr3/carbon in ambient environment without humidity control, reaching a PCE of 6.7% and good tolerance in humid air and extreme temperatures [5]. Tang’s group further boosted the PCEs of CsPbBr3 allinorganic PSCs from 6.7% to 10.6% by using interfacial or compositional engineering [12,13,14] Despite these achievements, the charge-carrier trap states within the CsPbBr3 film and the interface still impede the further improvements of the device performances [13, 15]. Arising from the improved charge transfer rate, the optimized device exhibits a PCE of 8.64%, which is 20% higher than the device without QD intermediate layer
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