Emerging Biomedical Applications of Organic Light‐Emitting Diodes

Abstract

As solid‐state light sources based on amorphous organic semiconductors, organic light‐emitting diodes (OLEDs) are widely used in modern smartphone displays and TVs. Due to the dramatic improvements in stability, efficiency, and brightness achieved over the last three decades, OLEDs have also become attractive light sources for compact and “imperceptible” biomedical devices that use light to probe, image, manipulate, or treat biological matter. The inherent mechanical flexibility of OLEDs and their compatibility with a wide range of substrates and geometries are of particular benefit in this context. Here, recent progress in the development and use of OLEDs for biomedical applications is reviewed. The specific requirements that this poses are described and compared to the current state of the art, in particular in terms of the brightness, patterning, stability, and encapsulation of OLEDs. Examples from several main areas are then discussed in some detail: on‐chip sensing and integration with microfluidics, wearable devices for optical monitoring, therapeutic devices, and the emerging use in neuroscience for targeted photostimulation via optogenetics. The review closes with a brief outlook on future avenues to scale the manufacturing of OLED‐based devices for biomedical use.

Wearable electronics for skin wound monitoring and healing

“…It has been defined as "a form of light treatment that utilizes nonionizing forms of light sources, including lasers, light-emitting diodes (LEDs), and broadband light, in the visible and infrared spectrum, involving a nonthermal process with endogenous chromophores eliciting photophysical (i.e., linear and nonlinear) and photochemical events at various biological scales. This treatment results in beneficial therapeutic outcomes including, but not limited to, the alleviation of pain or inflammation, immunomodulation, and promotion of wound healing and tissue regeneration" [86,96,97] . The second one is photodynamic therapy (PDT).…”

Light extraction from organic light emitting diodes (OLEDs)

“…In addition to cost, an ongoing related impediment leading to this situation is the issue of OLED efficiencies and the light outcoupling or extraction factor η out , which is the fraction of photons emitted into the forward (viewing) hemisphere. Earlier reviews have addressed different aspects of this issue [1][2][3][4][5][6][7]. The external quantum efficiency η EQE , i.e.…”

Fabrication and biocompatibility analysis of flexible organic light emitting diodes on poly(lactic acid) substrates: toward the development of greener bio‐electronic devices

“…Additionally, solid state lighting devices in particular show multiple applications in the field of photodynamic therapy, optogenetic, sensing, as well as wearable displays 10 . A very promising solid‐state lighting technology is represented by the organic light emitting diode (OLED) one, since it combines excellent properties in terms of luminous efficiency and intrinsic characteristics of organic materials 4,11,12 . Organic materials are soft, flexible, and often biocompatible and hence they can be properly exploited for the design of bio‐optoelectronic devices.…”

“…That makes the OLEDs versatile in different application fields since the color emitted by them can be chosen in order to satisfy different needs. In particular, in biological applications the emission wavelength is an important parameter: in phototherapy a specific wavelength is delivered to a photosensitizer in order to produce singlet oxygen which is able to interact with cancer cells and bacteria; in optogenetics, the light is used to control genetically modified neurons and a good overlap with the absorption spectrum of the light sensitive protein is crucial to achieve the stimulation; health monitoring systems for the heart pulse measurements or oximeters require light emitting devices with different emitted wavelengths 12 . Therefore, the choice of the active materials is the first step to address a bio‐electronic OLED device.…”

“…10 A very promising solid-state lighting technology is represented by the organic light emitting diode (OLED) one, since it combines excellent properties in terms of luminous efficiency and intrinsic characteristics of organic materials. 4,11,12 Organic materials are soft, flexible, and often biocompatible and hence they can be properly exploited for the design of bio-optoelectronic devices. Moreover, currently the commercially available luminescent organic materials are characterized by different emission spectra such to cover almost the entire visible wavelength range.…”