Transparent photodetectors with ultra-low dark current and high photoresponse for near-infrared detection

Developing efficient small molecule-based organic photo-couplers by optimizing the cathode interfacial layer in the photodetector

“…S6(a), ESI†), the spectral responsivity could be expressed further as the formula presented below. 27,64 where λ is the wavelength of the photon (nm), h is Planck's constant (6.626 × 10 −34 J s), and c is the velocity of light (2.998 × 10 8 m s −1 ). As plotted in Fig.…”

“…S6(a), ESI †), the spectral responsivity could be expressed further as the formula presented below. 27,64…”

“…26 In an independent study, Hadiyanto et al have introduced 25 nm of N , N ′-bis-(1-naphthyl)- N , N ′-diphenyl-1,1′-biphenyl-4,4′-diamine (NPB) and 3 nm of BPhen as the blocking layers in a transparent OPD device with an optimized blending ratio as the active layer (40 nm), successfully demonstrating the suppression of dark current density without sacrificing the EQE. 27 Moreover, lithium fluoride doped C 60 (C 60 :LiF) has been used as the hole blocking layer (HBL) to achieve an ultra-low dark current density by reducing the trap-induced current generated at the interface. 28 Compared to C 60 fullerenes, C 70 fullerenes as the acceptor in BHJ show a wide optical absorption range in visible light.…”

“…29 Hadiyanto et al have successfully demonstrated strong optical absorption in the nearinfrared (NIR) region with chloroaluminium phthalocyanine (ClAlPc) as a donor blended with C 60 as an acceptor. 27 Despite the drawbacks, due to relatively better electron mobility and suitable ionization potential (IP), C 60 fullerene or its derivatives are effectively used as an interfacial modifier in the metal electrode facilitating electron extraction and inhibiting charge recombination as a cathode interlayer (or HBL). 19,[30][31][32][33] Unfortunately, the interfacial dipoles form trap states to the photoexcited electrons, resulting in the reduced responsivity of the devices.…”

Theoretical and Experimental Investigation of Barrier‐Energy‐Dependent Charge Injection Mechanisms in Organic Photodetectors

“…The sources of injected charge carriers have been studied, and various causes such as band offset of semiconductors, [18] thermal generated charge, [19][20][21] shunt leakage, [22,23] and tunnel ling [18,20] were suggested, as shown in Figure S1a (Supporting Information). Since most of conducting polymerbased bulk heterojunction (BHJ) structures do not form bigger grain boundaries than their thickness, [22] unlike inorganic semicon ductor materials, the shunt leakage in BHJ structure is mainly caused by the vertical arrangement, unless each electrode is formed close enough to contact each other due to etching of the BHJ structures as in case 3 of Figure S1a (Supporting Infor mation).…”