Optimization and Development of ITO-Free Plasmonic Gold Nanoparticles Assisted Inverted Organic Solar Cells

This paper focuses on the fabrication of an ITO-free plasmonic assisted inverted organic solar cell (OSC) constituting aluminium doped zinc oxide (AZO) as front cathode and ultraviolet (UV) filtering layer. The gold nanoflowers are introduced in the device to increase the efficiency using localized surface plasmon resonance (LSPR) shown by plasmonic nanoparticles. We used GPVDM software to first optimize the cell, based on the geometry AZO/ZnO/PTB7:PC71BM/MoO3/Ag where AZO acts as the transparent conducting oxide (TCO) cathode and UV filter, zinc oxide (ZnO) behaves as the electron transport layer (ETL), Thieno[3,4 b]thiophene-alt-benzodithiophene: [6,6]-phenyl C71 butyric acid methyl ester (PTB7: PC71BM) mixture as the active layer, molybdenum trioxide (MoO3) as the hole transport layer (HTL) and silver (Ag) serves as the anode layer. By modelling, we find that the optimized device with maximum power conversion efficiency (PCE) includes 10 nm thick HTL, 200 nm thick photoactive layer and ETL thickness of 30 nm. Using the optimized thicknesses, we have fabricated three structurally identical inverted OSCs: first having AZO as the front cathode (AZO based device); second with ITO as the front cathode (ITO based control device); third includes AZO as cathode and plasmonic gold nanoflowers embedded inside the active layer (plasmonic assisted AZO based device). The AZO based device exhibited the PCE value of 6.19%, slightly less than the efficiency of 6.83% for ITO based control device. However, a remarkable increase in the lifetime was achieved for AZO based device under UV assisted acceleration ageing test. The stability enhancement of AZO based device is because of the UV filtering properties of AZO which prevent degradation in the device due to UV exposure. Also, the PCE of AZO based device was further enhanced to 7.01% when plasmonic gold nanoparticles were included in the active layer. This work provides a feasible way to develop an ITO free plasmonic assisted inverted organic solar cell to achieve cost-effectiveness, high efficiency and stability.

DFT Based Modeling of Asymmetric Non-Fullerene Acceptors for High-Performance Organic Solar Cell

AbstractFive new asymmetric NFA-based polymer solar cells i.e., N1-N5 are designed by doing modification in terminal groups of the acceptor part of experimentally synthesized reference molecule with (4,4,9,9-tetramethyl-4,9 dihydroselenopheno [2’,3’:5,6]-s-indaceno [1,2-b] thiophene) core. Frontier molecular orbital analysis is used to study their photovoltaic and optoelectronic properties. It confirmed the electrons' transportation from the donor to the acceptor part. It stated that all molecules have a lower bandgap than R and N2 has the lowest bandgap of 2.01 eV. The molecular orbital potential analysis confirmed the electron-withdrawing properties of the terminal groups. Optical properties studies evaluated maximum absorption with transition energies. All newly designed molecules N1-N5 show higher λmax values than R i.e., in the range of 680-740 nm with N2 having the highest λmax of 735 nm and lowest transition energy of 1.69 eV. Dipole moment studies showed that N3 has a maximum dipole moment of 7-40 D with all others having comparable values. TDM plots confirmed the electron shifting from donor to acceptor region. Reorganization energy analysis showed that N1 and N3 have the lowest reorganization energy values thus giving the highest electron mobilities. Voc calculated results of all molecules N1-N5 have lower values than R when coupled with PTB7-Th donor polymer. Charge transport analysis of N2 and PTB7-Th coupled molecule confirmed the acceptor type nature of our designed molecules.

Modeling of optical characteristics of organic solar cells based on poly (3,4-ethylene dioxythiophene): polystyrene sulfonate with incorporated silver nanoparticles

Changing the geometric parameters of the elements of the organic solar cell (OSC) and its components, changes in its optical characteristics such as reflection, absorption and transmission of light were studied. In the simulation, the main elements influencing the change in the characteristics of the OSC were poly (3,4-ethylenedioxythiophene): polystyrene sulfonate (PEDOT: PSS), poly (3-hexylthiophene): [6,6] phenyl-C61butyric acid methyl ester (P3HT: PCBM) on silver nanoparticles. The dimensions of silver nanoparticles coincide with the thickness of the PEDOT layer (50 nm) in which they are located, the particle diameter is 45 nm, the thickness of the P3HT: PCBM layer has always remained equal to 100 nm. The peak at a wavelength of about 726 nm, when there are silver particles in the OSC, indicates the presence of localized surface plasmon resonance (LPPR), which causes a local amplification of the electromagnetic field near the surface of metal nanoparticles. LPPR induced by silver nanoparticles not only increases the degree of light absorption, but also enhances the degree of exciton dissociation. As a result, photocurrent and overall OSC efficiency can be significantly improved due to LPPR.