Review—Light Emission from Thin Film Solar Cell Materials: An Emerging Infrared and Visible Light Emitter

Abstract

In the last decade, there have been extensive studies on fabrication and physics of thin-film solar cell materials and devices. Many high-efficiency solar cell devices have been developed, and the knowledge gained in these studies can be used advantageously to produce bright light-emitting devices. In this review, we summarize recent luminescence spectroscopic studies on new solar-cell materials and discuss their photocarrier dynamics with respect to efficient light emission. © The Author(s) This special issue focuses on fundamental researches and applications for light emitters and phosphors in the infrared and visible spectral region. Here, we would like to introduce novel approaches, applying insights from thin-film solar-cell materials to the development of new light emitting materials. Recent progress in fundamental research on solar cells is remarkable as novel materials such as perovskite thin films, quantum dots, and colloidal nanocrystals being applied to fabrication of solar cells. Huge efforts in this fundamental research area lead to conversion efficiency improvements for many types of solar cells.1 There exist global demands and attention in establishments of affordable, flexible, light-weight and high conversionefficiency devices.The prerequisite as a light absorber for high-efficiency thin-film solar cells, is a direct band-gap semiconductor with large absorption coefficient and band-gap in the near infrared and visible spectral region. 2One of the best indicators of the intrinsic material quality of a semiconductor, which in turn directly determines the carrier loss in a device, is the internal luminescence quantum efficiency. Therefore, highly luminescent semiconductors are excellent light absorber materials for solar cells [3][4][5][6][7][8] and allow for high open-circuit voltages. 2,9 Reversely, excellent solar-cell light absorber materials could be excellent lightemitting materials. In fact, the electroluminescence (EL) measurement is a well-established and widely-used technique for characterizing solar cell devices.10-17 Furthermore, time-resolved photoluminescence (PL) spectroscopy based on modern laser techniques have revealed the charge carrier flow in bulk materials as well as in devices.18-23 PL and EL spectroscopy techniques are not limited to material characterization, but are also able to characterize devices. Taking account of these close relations, utilizing insights and understandings obtained from solar cell research is strategic for developments in novel luminescent materials and devices in the near infrared and visible spectral region.In this short review, we briefly summarize luminescence properties of thin-film solar cell materials that have been recently developed as thin-film light absorbers. By further discussing the photocarrier dynamics, we are able to understand how these materials can be used optimally as light emitters in novel devices. The abundant information from solar cell research can be applied to other devices as well. A deep understanding of the carrier phy...

Review—Photoluminescence Characterization of Halide Perovskite Materials and Solar Cells

“…[9][10][11][12][13] PL spectroscopy can be used to understand the carrier dynamics of not only the materials themselves but also solar cell devices. [14][15][16] Optical studies have revealed that halide perovskites feature few localized levels within the bandgap and a corresponding sharp absorption edge, high PL efficiency, and excellent carrier properties, such as a long carrier lifetime, all of which together explain the high PCEs of perovskite solar cells. [17][18][19][20] Furthermore, it has been revealed that halide perovskites possess unique thermo-optic properties [21][22][23][24] and nonlinear optical responses, 25,26 which has attracted broad interest from researchers in fundamental semiconductor physics and device applications.…”

“…89 This is why determinations of carrier lifetimes by using time-resolved PL measurements have been indispensable in the photovoltaic field. 14,15 The PL lifetime is typically measured with pulsed laser excitation, while an actual solar cell operates under the steady-state conditions of continuous solar illumination. The photogenerated carrier densities often differ very much between pulsed laser excitation and continuous light illumination.…”

Band‐Edge Luminescence from Oxide and Halide Perovskite Semiconductors

“…In our investigations into the photophysics of semiconductors, we have found that a semiconductor can be considered potentially useful for optoelectronic device applications if it exhibits strong PL that corresponds to the material-specific band-gap energy. [11,33] We have shown that it is even possible to characterize the electrical properties of optoelectronic devices such as solar cells by using band-edge PL. [33,34] Compared with electrical conduction, PL properties are much more sensitive to impurities and defects.…”

“…[11,33] We have shown that it is even possible to characterize the electrical properties of optoelectronic devices such as solar cells by using band-edge PL. [33,34] Compared with electrical conduction, PL properties are much more sensitive to impurities and defects. Thus, crystals with extremely high quality are needed for PL measurements to be able to detect intrinsic optical processes.…”

The Influence of Helium Dielectric Barrier Discharge Jet (DBDjet) Plasma Treatment on Bathocuproine (BCP) in p-i-n-Structure Perovskite Solar Cells

“…In the past few years, organic-inorganic hybrid perovskite solar cells (PSCs) have gained attention due to their high power conversion efficiency (PCE) and low cost [1][2][3][4][5][6][7][8][9]. In 2013, the first p-i-n-structure PSC was fabricated and it had a PCE of 3.9% [10].…”