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.

A high‐efficiency and stable perovskite solar cell fabricated in ambient air using a polyaniline passivation layer

Over the past number of years, the power conversion efficiency of perovskite solar cells has remained at 25.5%, reflecting a respectable result for the general incorporation of organometallic trihalide perovskite solar cells. However, perovskite solar cells still suffer from long-term stability issues. Perovskite decomposes upon exposure to moisture, thermal, and UV-A light. Studies related to this context have remained ongoing. Recently, research was mainly conducted on the stability of perovskite against non-radiative recombination. This study improved a critical instability in perovskite solar cells arising from non-radiative recombination and UV-A light using a passivation layer. The passivation layer comprised a polyaniline (PANI) polymer as an interfacial modifier inserted between the active layer and the electron transport layer. Accordingly, the UV-A light did not reach the active layer and confined the Pb2+ ions at PANI passivation layer. This study optimized the perovskite solar cells by controlling the concentration, thickness and drying conditions of the PANI passivation layer. As a result, the efficiency of the perovskite solar cell was achieved 15.1% and showed over 84% maintain in efficiency in the ambient air for one month using the 65 nm PANI passivation layer.

Aluminum Doping Effects on Interface Depletion Width of Low Temperature Processed ZnO Electron Transport Layer-Based Perovskite Solar Cells

Rapid improvement in efficiency and stabilities of perovskite solar cells (PSCs) is an indication of its prime role for future energy demands. Various research has been carried out to improve efficiency including reducing the exciton recombination and enhancement of electron mobilities within cells by using electron transport material (ETM). In the present research, electrical, optical, and depletion width reduction properties of low temperature processed ZnO electron transport layer-based perovskite solar cells are studied. The ZnO thin films vary with the concentration of Al doping, and improvement of optical transmission percentage up to 80% for doped samples is confirmed by optical analysis. Reduction in electrical resistance for 1% Al concentration and maximum conductivity 11,697.41 (1/Ω-cm) among the prepared samples and carrier concentration 1.06×1022 cm−3 were corroborated by Hall effect measurements. Systematic impedance spectroscopy of perovskite devices with synthesized ETM is presented in the study, while the depletion width reduction is observed by Mott Schottky curves. IV measurements of the device and the interfacial charge transfer between the absorber layer of methylammonium lead iodide and ETM have also been elaborated on interface electronic characteristics.

The Effect of Energy Level of Transport Layer on the Performance of Ambient Air Prepared Perovskite Solar Cell: A SCAPS-1D Simulation Study

The perovskite solar cell (PSC) as an emerging and promising type has been extensively studied. In this study, a model for a PSC prepared in ambient air was established by using SCAPS-1D. After that, it was further analyzed through varying the defect density of the perovskite absorber layer (Nt), the thin film thickness and energy-level matching between the electron transport layer (ETL), the perovskite absorber layer and the hole transport layer (HTL), for a better understanding of the carrier features. The Nt varied from 1.000 × 1011 to 1.000 × 1017 cm−3. The performance of the solar cell is promoted with improved Nt. When Nt is at 1.000 × 1015 cm−3, the carrier diffusion length reaches μm, and the carrier lifetime comes to 200 nm. The thickness of the absorber layer was changed from 200 to 600 nm. It is shown that the absorber layer could be prepared thinner for reducing carrier recombination when at high Nt. The thickness effect of ETL and HTL is weakened, since Nt dominates the solar cell performance. The effect of the affinity of ETL (3.4–4.3 eV) and HTL (2.0–2.7 eV), together with three energy-level matching situations “ETL(4.2)+HTL(2.5)”, “ETL(4.0)+HTL(2.2)” and “ETL(4.0)+HTL(2.5)” on the performance of the solar cell were analyzed. It was found that the HTL with valence band 0.05 eV lower than that of the perovskite absorber layer could have a blocking effect that reduced carrier recombination. The effect of energy-level matching becomes more important with improved Nt. Energy-level matching between the ETL and perovskite absorber layer turns out counterbalance characteristic on Jsc and Voc, and the “ETL(4.0)+HTL(2.5)” case can result in solar cell with Jsc of 27.58 mA/cm2, Voc of 1.0713 V, FF of 66.02% and efficiency of 19.51%. The findings would be very useful for fabricating high-efficiency and low-cost PSC by a large-scale ambient air route.