Charge Transport between Coaxial Polymer Nanorods and Grafted All-Inorganic Perovskite Nanocrystals for Hybrid Organic Solar Cells with Enhanced Photoconversion Efficiency

Abstract

The versatile optoelectronic properties of perovskite nanocrystals (NCs) have provided a strong surge for their utilization in different classes of solar cells, with organic photovoltaic systems being no exception. In an unprecedented approach, a hybrid solar cell with CsPbBr 1.5 I 1.5 NCs strategically grafted on poly(3-hexylthiophene-2,5-diyl) (P3HT) nanorods (NRs) is shown to have a photoconversion efficiency of 9.72 ± 0.4%, with only 1.5 wt % NCs. The improvement is twice more than the P3HT:PCBM reference devices (4.09 ± 0.2%). The choice of NC composition is validated by density functional theory calculations, which show decent charge carrier mobility in CsPbBr 1.5 I 1.5 , besides having better stability than CsPbI 3 , making CsPbBr 1.5 I 1.5 NCs a suitable contender for hybrid device architecture. A trivial blending of the NCs in the P3HT:PCBM matrix results in their nonuniform distribution, escalating charge carrier trapping, albeit maintaining a device efficiency of 8.07 ± 0.3% with 1 wt % NCs. Uniform NC grafting is propitious over inhomogeneous blending because CsPbBr 1.5 I 1.5 NCs not only act as additional light harvesters, but their chemical grafting onto the P3HT NRs improves the charge transport by creating better charge percolation pathways. The higher crystallinity of the P3HT NRs than P3HT also helps in reducing the trap states.

Photodetectors with High Responsivity by Thickness Tunable Mixed Halide Perovskite Nanosheets

“…Br 3 and Br 1.5 I 1.5 NS and NC films remain stable even after 24 h. 8 Due to the better surfactant coverage of the I 3 NS films, the orthorhombic γ-phase is retained up to 6 h while the NCs degrade within 30 min (Figure S9i−l). The electronic band structure calculations by the density functional theory (DFT) formalism as implemented in Wien2k code (Figure S10) 38,39 show that the cohesive energy derived from the optimized structures is −14.91, −13.65, and −12.78 eV for Br 3 , Br 1.5 I 1.5 , and I 3 NSs, respectively, which demonstrate the better structural stability of Br 3 and Br 1.5 I 1.5 NSs. The Pb 6p orbital contributes to the conduction band minimum (CBM), and the valence band maximum (VBM) is derived from an admixture of Br 4p and I 5p states.…”

Heterovalent Substitution in Mixed Halide Perovskite Quantum Dots for Improved and Stable Photovoltaic Performance

“…The self-consistent convergence calculations were considered similar to the earlier calculation of a total energy tolerance of 10 −5 Ry. 38 The similar ionic radius of Ag + (115 pm) and Pb 2+ (119 pm) helped to increase the tolerance factor, and the device performance is better than that of other elemental substitutions (e.g., Sn 2+ , Sr 2+ , In 3+ , and so forth). However, due to an odd number of valence electrons in the Ag atom there is a slight change in the crystal structure.…”

“…The size of K -point meshes of the CsPbI 1.5 Br 1.5 super cell and CsPb 1– x Ag x I 1.5 Br 1.5 structure is set to 6 × 6 × 6. The self-consistent convergence calculations were considered similar to the earlier calculation of a total energy tolerance of 10 –5 Ry . The similar ionic radius of Ag + (115 pm) and Pb 2+ (119 pm) helped to increase the tolerance factor, and the device performance is better than that of other elemental substitutions (e.g., Sn 2+ , Sr 2+ , In 3+ , and so forth).…”

Inorganic Halide Perovskite Quantum Dots: A Versatile Nanomaterial Platform for Electronic Applications

“…For perovskite QDs, although different experimental techniques often render different values, their composition-dependent carrier mobilities are generally in the same trend as polycrystalline thin films. Take allinorganic perovskites CsPbX 3 as examples, both the theoretical and experimental results verified that CsPbI 3 QDs have the highest carrier mobility of 20 cm 2 V −1 s −1 [83], followed by CsPbBr 3 (~ 2.1 cm 2 V −1 s −1 ) [84] and CsPbCl 3 [85][86][87]. Likewise, as suggested by TRPL results, CsPbI 3 QDs also own the longest lifetime of 29 ns, while CsPbCl 3 has the shortest lifetime of 1 ns [16].…”