Search

Donor PM6 and acceptor L8‐BO are employed to build semitransparent organic photovoltaics (ST‐OPVs). Opaque OPVs are fabricated by tuning the spin‐coating speed of PM6:L8‐BO solution to optimize the photon utilization by balancing photon harvesting and photogenerated carrier collection. The optimal opaque OPVs exhibit relatively high fill‐factor (FF) of 77.58% and power conversion efficiency (PCE) of 15.07%, the average visible transmittance (AVT) of corresponding PM6:L8‐BO films arrives to 53.25%, indicating great potential in realizing efficient ST‐OPVs. ST‐OPVs are built with 1 nm Au/(10, 15, 20, 25 nm) Ag as cathode, exhibiting the PCE/AVT of 11.53%/22.57%, 13.20%/14.24%, 14.28%/9.34%, and 14.71%/6.77%, respectively. Colorful ST‐OPVs are achieved by coupling different Ag/LiF/Ag Fabry‐Pérot (F‐P) resonator microcavity. Green ST‐OPVs with varied color coordinates are achieved by fixing LiF layer thickness as 110 nm and varying Ag layers′ thickness, originating from the adjusted transmittance spectra of green ST‐OPVs. Upon fixing Ag layers′ thickness as 15/25 nm and varying LiF layer thickness as 90, 110, and 145 nm, ST‐OPVs present colors of blue, green, and red with corresponding transmittance peak at 474, 553, and 657 nm. The corresponding PCE/peak transmittance (Tpeak) values arrive to 13.80%/37.8%, 13.31%/28.4%, and 13.20%/27.7%, which should be the best performance among reported colorful ST‐OPVs. [ABSTRACT FROM AUTHOR]

Fullerene-derivatives based bulk heterojunctions hold an exceptionally important role on the roadmap of highly efficient organic solar cells (OSCs). In recent years, the utilization of the non-fused ring acceptors based OSCs has further improved photovoltaic power conversion efficiencies. Among these, one of the fundamental issues is to explore and to understand the spin-related polaron dissociation at charge transfer states because they act as the central unit for the photovoltaic action. It is also eagerly important to quantify some internal fields, such as hyperfine fields and the spin–orbit coupling. The aim of the work is to develop a method for unraveling the photoexcited spin states, particularly for the fullerene-derivative based OSC. Furthermore, it helps to elucidate a long-standing issue regarding the relatively high production of photocurrent for the P3HT:PC71BM system, which is indeed contrary to its counterpart the P3HT:PC61BM system. Their corresponding Jablonski diagrams have been determined in order to understand interior spin dynamics. The method of the study offers an alternative route for an understanding of device performance from the spin-related aspect. [ABSTRACT FROM AUTHOR]

Layer‐by‐layer all‐polymer solar cells (LbL all‐PSCs) are prepared with PM6 and PY‐IT by using sequential spin coating method. The exciton dissociation efficiency in acceptor layer near electrode is rather low due to the limited exciton diffuse distance and impossible energy transfer from narrow bandgap acceptor to wide bandgap donor. In this study, less PM6 is incorporated into PY‐IT layer to enhance exciton dissociation in PY‐IT layer near electrode. A power conversion efficiency (PCE) of 17.45% is achieved in the LbL all‐PSCs incorporating 10 wt% PM6 into PY‐IT layer, which is much larger than 16.04% PCE of PM6/PY‐IT‐based LbL all‐PSCs. Over 8% PCE enhancement can be realized by incorporating 10 wt% PM6 into PY‐IT layer, which is attributed to the enhanced exciton utilization efficiency in PY‐IT layers near electrode. The enhanced exciton utilization efficiency in PY‐IT layer can be confirmed from the quenched photoluminescence (PL) emission in PY‐IT:PM6 films. Meanwhile, charge transport in acceptor layers can be optimized by incorporating less PM6, as confirmed from the optimized molecular arrangement. This study indicates that the strategy of incorporating less donor into acceptor layer has great potential in fabricating efficient LbL all‐PSCs by improving exciton utilization efficiency in acceptor layer near electrode. [ABSTRACT FROM AUTHOR]

Filter‐free narrowband photomultiplication‐type planar heterojunction (PHJ) organic photodetectors (PM‐PHOPDs) are first realized by employing a thick front donor layer and an ultrathin PC71BM layer. The thick front donor layer is employed as an optical field adjusting (OFA) layer. The sequentially coated PC71BM will diffuse slightly into OFA layer, which works as interfacial electron traps to capture photogenerated electrons for assisting hole tunneling injection. The P3HT/PC71BM‐based PM‐PHOPDs exhibit narrowband response with full‐width of half‐maximum of 32 nm and external quantum efficiency (EQE) of 1700% at 650 nm under −20 V bias. Due to the enhanced hole transport and reduced charge recombination in PHJ compared to those in bulk heterojunction (BHJ), the EQE of P3HT/PC71BM‐based narrowband PM‐PHOPDs is twice as P3HT:PC71BM BHJ‐based narrowband PM‐OPDs under the same bias. The response peak of PM‐PHOPDs is adjusted from 650 to 695 or 745 nm by incorporating SMPV1 or DRCN5T in OFA layers due to the red‐shifted absorption edge. The EQEs of 3600% at 695 nm and 870% at 745 nm are obtained for P3HT:SMPV1 and P3HT:DRCN5T‐based PM‐PHOPDs under −20 V bias, respectively. This work provides a smart strategy to achieve narrowband PM‐OPDs by designing different OFA layers. [ABSTRACT FROM AUTHOR]

Amplified spontaneous emission (ASE) has become a common phenomenon in hybrid perovskites by establishing coherent light-emitting excitons. This paper reports a new phenomenon that the long–range orbit–orbit interaction is established through orbital polarizations between coherent light-emitting excitons during the generation of ASE in the CsPbBr3 microrods. Essentially, when the orbital polarizations are optically generated with the same direction between coherent light-emitting excitons by using a circularly polarized pumping beam, the ASE amplitude can be largely enhanced by 22.3%, as compared to the situation when the orbital polarizations are generated with opposite directions by using linearly polarized photoexcitation in randomly orientated microstructures. This observation provides evidence that long–range orbit–orbit interaction occurs between coherent light-emitting excitons in ASE. Furthermore, the long–range orbit–orbit interaction between coherent light-emitting excitons is simultaneously increased with the ASE amplitude while increasing the pumping fluence. Therefore, the long–range orbit–orbit interaction plays an important role in developing coherent light-emitting excitons towards ASE in metal halide perovskites. [ABSTRACT FROM AUTHOR]

Quasi-two-dimensional (2D) perovskite light-emitting diodes are promising light sources for color display and lighting. However, poor carrier injection and transport between the bottom hole transport layer (HTL) and perovskite limit the device performance. Here we demonstrate a simple and effective way to modify the HTL for enhancing the performance of perovskite light-emitting diodes (PeLEDs). An electrolyte K 2 SO 4 is used to mix with poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS) as the hole transport layer. The K + doping helped the quasi-2D perovskite phases grow vertically along the interface of the PEDOT:PSS, fine-modulate the phase distribution, and simultaneously reduce the defect density of quasi-2D perovskites. It also significantly reduced the exciton quenching and injection barrier at PEDOT:PSS and quasi-2D perovskite interface. The optimized green PeLEDs with the K 2 SO 4 doped PEDOT:PSS HTL showed a maximum luminance of 17185 cd/m 2 which is almost 4.7 times brighter than the control one, with a maximum external quantum efficiency of 18.64%.

Methylammonium lead iodide (CH 3 NH 3 PbI 3 ), with the organic-inorganic hybrid perovskite (OIHP) structure, has gained tremendous research interest due to its excellent photo-electron conversion ability in the application of photovoltaics. Despite its solution processed polycrystalline thin film form in solar cells, the single crystalline counterpart may offer some incredibly novel optoelectronic functionalities. In this work, a sizable (>5 mm) and high quality CH 3 NH 3 PbI 3 single crystal has been synthesized by the inverse temperature crystallization method, and a white-light photodetector of the structure glass/ITO/Ga/ CH 3 NH 3 PbI 3 /Au was fabricated. Overbroad photo-excitation intensities ranging from 0.1 mW/cm 2 to 100 mW/cm 2 using a sun-light simulator, the on-off ratio is tunable in a wide-range from 65 to 2250 at zero bias voltage. The responsivity (R) and detectivity (D*) are 36.2 mA/W and 2.68×10 11 Jones respectively at a weak white-light intensity such as 0.1 mW/cm 2 . Both the photodetective parameters decrease with the increase of the illumination intensity. Based on impedance spectra obtained at working condition and light intensity dependent J sc measurements, the surface trap-assist recombination may play a dominating role. The corresponding lifetime (τ surf ) and resistance (R surf_trap ) exhibit fast decays at higher illumination intensities. This fundamental study may pave the way for exploring the contribution of the surface trap-assist recombination in the CH 3 NH 3 PbI 3 single crystal based photodetector. We believe it is applicable for integration in micro-photonics for sensitive and weak white-light photo-detection.