Recent Advances in Organic Photovoltaics: Device Structure and Optical Engineering Optimization on the Nanoscale

Abstract

Organic photovoltaic (OPV) devices, which can directly convert absorbed sunlight to electricity, are stacked thin films of tens to hundreds of nanometers. They have emerged as a promising candidate for affordable, clean, and renewable energy. In the past few years, a rapid increase has been seen in the power conversion efficiency of OPV devices toward 10% and above, through comprehensive optimizations via novel photoactive donor and acceptor materials, control of thin-film morphology on the nanoscale, device structure developments, and interfacial and optical engineering. The intrinsic problems of short exciton diffusion length and low carrier mobility in organic semiconductors creates a challenge for OPV designs for achieving optically thick and electrically thin device structures to achieve sufficient light absorption and efficient electron/hole extraction. Recent advances in the field of OPV devices are reviewed, with a focus on the progress in device architecture and optical engineering approaches that lead to improved electrical and optical characteristics in OPV devices. Successful strategies are highlighted for light wave distribution, modulation, and absorption promotion inside the active layer of OPV devices by incorporating periodic nanopatterns/nanostructures or incorporating metallic nanomaterials and nanostructures.

Effects of Nanoimprinted Structures on the Performance of Organic Solar Cells

“…Recent advances in material synthesis and device fabrication for the solution processed organic solar cells (OSCs) have led to power conversion efficiencies (PCEs) exceeding 11% using hole transporting conjugated polymers and electron transporting organic molecules [1][2][3][4][5][6][7][8]. Bulk heterojunctions are formed in the active layers of the OSCs.…”

“…Bulk heterojunctions are formed in the active layers of the OSCs. Even though the device performance of the OSCs has been improved significantly [3][4][5][6], their PCEs are still lower than those of their inorganic counterparts, which remain a hindrance towards their commercialization. One of the factors that limit the performance of the OSCs is the relatively lower charge carrier mobility of the organic materials, which results in trapping of the photogenerated charge carriers from the junction to the electrodes [9,10].…”

A Review of Organic Photovoltaic Energy Source and Its Technological Designs

“…Recently, there have also been remarkable research efforts to develop insights of the combined science of organic semiconductors and the associated OPV technology with emphasis on enhancements of PCEs [14,95,[97][98][99] and stability of OSC devices [1]. For example, different OPV material tailoring approaches [14,[29][30][31][32][33][34] along with wide ranges of technological OSC designs and configurations have been established [100][101][102][103]. Undeniably, these efforts have led to extensive improvements of the characteristic performances of OPV material structures and PCEs of BHJ OSC devices and components [14,28,[92][93][94][95][96][97][98][99][100][101][102][103].…”

“…Besides experimentally engineered polymeric functional materials and corresponding investigations of OPV devices [28][29][30][31][32][33][34][92][93][94][95][96][97][98][99][100][101][102][103][104], electrical models are also increasingly being developed to ascertain the dependency of OSC performances on their structural and material properties [17,99]. These models are developed generally based on one spatial dimensional solar cell electrical systems and concepts [17,[104][105][106][107][108][109].…”

Toward high volume solution based roll-to-roll processing of OLEDs

“…[1][2][3] Relatively efficient OLEDs have already been demonstrated some decades ago where the organic semiconducting layers were deposited as thin films by evaporation. 4,5 A typical OLED device architecture is shown in Fig.…”