Enhanced Open-Circuit Voltage in Subphthalocyanine/C₆₀ Organic Photovoltaic Cells

Abstract

A double-heterostructure boron subphthalocyanine chloride (SubPc)/C60 thin-film photovoltaic cell exhibits a more than doubled Voc compared to a conventional copper phthalocyanine (CuPc)/C60 cell under 1 sun AM1.5G simulated illumination. The lower oxidation potential of SubPc results in an increase in the energy difference between the lowest unoccupied molecular orbital of the acceptor-like material and the highest occupied molecular orbital of the donor-like material (referred to as the interface gap, Ig) by 400 meV. We attribute the significant increase in Voc to this increase in Ig.

Enhanced photovoltaic conversion efficiency in bulk heterojunction solar cells upon incorporating nanohybridized PbS quantum dots/multiwall carbon nanotubes

“…In all our devices, the P3HT was used as donor with respect to the PCBM and/or nanohybrid of QD/CNT as the acceptor(s). We presume that the V oc can be attributed to the energy difference between the HOMO of P3HT and LUMO of PCBM in our standard cell as it has been reported by other research groups [42][43][44][45][46][47]. Since the value of conduction band of PbS-QDs is consistently aligned with the LUMO value of PCBM [1,14,28] as shown in Figure 7, therefore it is obvious that the V oc of hybrid device -I is consistent with the standard P3HT:PCBM devices.…”

“…However, it can be quantified by the energy difference between the lowest unoccupied molecular orbital (LUMO) of the acceptor -and the highest occupied molecular orbital (HOMO) of the donor -type materials at the heterojunction interface [42][43][44]46,47]. We explain the charge transport mechanism(s) behind the consistently observed V oc in all our devices with the aid of energy band diagram shown in Figure 7.…”

“…Until now, it has been long-debated in literature to address the exact mechanism for the origin of V oc in photovoltaics and has been still under investigation [42][43][44][45][46][47]. However, it can be quantified by the energy difference between the lowest unoccupied molecular orbital (LUMO) of the acceptor -and the highest occupied molecular orbital (HOMO) of the donor -type materials at the heterojunction interface [42][43][44]46,47].…”

Electronic transitions and band offsets in C60:SubPc and C60:MgPc on MoO3 studied by modulated surface photovoltage spectroscopy

“…The values of E H and E L are 5.6 and 3.6 eV, respectively, for layers of SubPc molecules. 23 The absorption coefficients of SubPc or MgPc layers are as high as 3 Â 10 5 cm À1 between 450 and 650 nm. 24 The absorption of MgPc is extended to a range up to 850 nm and the values of E H and E L are 5.4 and 3.9 eV, respectively.…”

Carrier injection dynamics in heterojunction solar cells with bipolar molecule

“…[3][4][5][6][7][8] Reflecting the bipolar nature, 8 SubPc can be used even as a donor material in heterojunction OSCs with C 60 as an acceptor. 9,10 Especially, the bipolar nature of SubPc and SubNc enables cascade heterojunction OCSs, 3,[5][6][7] whose PCEs reach to 8.4%. 3 However, the carrier injection dynamics in the heterojunction OSCs with bipolar molecule remains unclear.…”