Decoupling the optical and electrical properties of subphthalocyanine/C₇₀bi-layer organic photovoltaic devices: improved photocurrent while maintaining a high open-circuit voltage and fill factor

Abstract

Optimizing performance of fullerene-based small-molecule bi-layer organic photovoltaic devices.

Improving Performance and Lifetime of Small-Molecule Organic Photovoltaic Devices by Using Bathocuproine–Fullerene Cathodic Layer

“…17,57−59 Therefore, we propose a modified model by replacing R SH with a bias-dependent term, R SH0 ± βVR SH0 , where β represents the trap dependence and the operation (addition or subtraction) depends on the polarity of the applied bias. 20 The proposed modified model can precisely predict the J−V curves under reverse biases (Supporting Information Figure S5). Although the modified model cannot fit the experimental results for small forward biases, as shown in the insets of Supporting Information Figure S5, the fits were consistent with the J−V curves for higher biases.…”

“…The calculated power dissipation profiles provided direct evidence of photon absorption by the active layers. 20 Figure 1 shows the calculated results. All devices showed similar profiles, and there were slight differences between the profiles of the device with a BCP buffer layer and that of the device with a BCP:C 60 buffer layer.…”

“…In bilayer OPV devices, the FF can reach its highest value if the device structure was optimized. 20,54 In the current study, the device structure was almost optimized through the control of the SubPc and C 60 thicknesses. Therefore, the improved IQE primarily contributed to the increase in J SC while maintaining the high FF.…”

“…16−18 In our previous studies, we demonstrated that the thickness variation of C 60 and C 70 enables manipulating the optical field distribution in OPV devices with different donor materials. 19,20 This optical tuning property is a consequence of the first optical field maximum occurring close to the reflective metal because of optical interference. 21−23 However, the wide absorption band of C 60 and C 70 may increase unnecessary absorption in OPV devices.…”

“…These excitons must diffuse to the donor/acceptor interface to overcome the binding energy and dissociate into free electrons and holes . Conventional OPV devices use fullerenes such as C 60 and C 70 as an acceptor; fullerenes have a large excition diffusion length. − Therefore, an exciton-blocking layer (EBL) is necessary to prevent the quench of excitons near the electrode and thereby increase the possibility of exciton dissociation. − In our previous studies, we demonstrated that the thickness variation of C 60 and C 70 enables manipulating the optical field distribution in OPV devices with different donor materials. , This optical tuning property is a consequence of the first optical field maximum occurring close to the reflective metal because of optical interference. − However, the wide absorption band of C 60 and C 70 may increase unnecessary absorption in OPV devices. , Therefore, using C 60 and C 70 as optical spacers may be inappropriate for optical field manipulation.…”