We report the temperature/time-dependent crystallization of poly(3-hexylthiophene) (P3HT) in blend films of P3HT and [6,6]-phenyl-C(61)-butyric acid methyl ester (PC₆₁BM). The crystallization behaviour of P3HT:PC₆₁BM blend films was measured as a function of annealing time at two different temperatures (150°C and 160°C) by employing a synchrotron-radiation grazing-incidence angle X-ray diffraction (GIXD) technique. The crystallization behaviour was correlated with corresponding solar cells annealed under the same conditions. Results showed that the trend of device performance was almost in accordance with that of the (100) GIXD intensity, indicating that the nanostructure change in blend films does affect the device performance. However, the intermediate zones related to nanomorphology fluctuations, which were observed for lower temperature (140°C) annealing, were significantly suppressed at higher temperature (150°C and 160°C) annealing.

We report the effect of hole-transporting material (HTM) addition on the performance of polymer solar cells based on blends of poly(3-hexylthiophene) (P3HT) and soluble fullerene. N,N 0 -Diphenyl-N,N 0 -bis(3-methylphenyl)-[1,1 0 -diphenyl]-4,4 0 -diamine (TPD) was chosen as a HTM because it is one of the well-established HTMs despite its drawback of wide band gap (3.1 eV) for solar cell applications. Two specialized measurement systems, synchrotron radiation grazing incidence angle X-ray diffraction (GIXD) and phase-mode atomic force microscopy (AFM), were employed to understand the correlation between device performance and nanostructures of blend films. Results showed that the addition of 3-7 wt% TPD improved the short circuit current density of unannealed devices due to the improved P3HT crystallization induced by the presence of TPD molecules. Although the short circuit current density of the binary blend device was recovered to the highest value after thermal annealing, the improved fill factor of TPD-added ternary blend devices at the 3-7 wt% TPD content led to the slightly enhanced power conversion efficiency at 3 wt% TPD in spite of reduced optical absorption in the ternary blend film.

Abstract:The combination of lithium ion battery (LIB) and organic (polymer) solar cells is expected to deliver versatile self-rechargeable portable energy sources, but less attention has been paid to the charging characteristics of LIB-using polymer solar cells. Here we demonstrate that the LIB packs, which were prepared by using lithium cobalt oxide (LiCoO 2 ) and graphite as a cathode and an anode, respectively, can be effectively charged by semi-solar modules of polymer:fullerene solar cells, of which bulk heterojunction (BHJ) layers are composed of poly(3-hexylthiophene) (P3HT) and [6,6]-phenyl-C61-butyric acid methyl ester (PC 61 BM). Results showed that the performance of semi-solar modules was not much degraded by connecting four single solar cells in series or in parallel, but their output power density was noticeably reduced by extending the number of single cells up to eight. The charging test disclosed that the output current density is of importance to speed up the LIB charging at the same output voltage.

Abstract:Here we report improved operation stability of passive matrix organic light-emitting displays (PM-OLED) by melting a hole-injecting layer (HIL) that is the first organic layer contacting anode. The PM-OLED displays fabricated in this work are consisted of 128 128 pixels in which each pixel has a dimension of 200μm 200μm. The exact thermal transition behaviour of hole-injecting material was first examined using a differential scanning calorimeter in order to decide the melting temperature for the HIL melting process (300 o C/3min). Results show that the display with the untreated (ascoated) HIL exhibited large leakage current which eventually resulted in damages (black cross-talk lines) to the display during operation. However, no cross-talk defect was observed for the PM-OLED display with the thermally treated (melted) HIL, which was supported by the absence of leakage current at reverse bias.Since the breakthrough works on organic light-emitting devices (OLED) based on either low-molecular-weight materials (i.e., small molecules) [1] or polymers [2], OLED displays are now in market even though their applications are limited to small size display for MP3 players, mobile phones, car front panel devices, shavers, etc [3,4]. This successful debut of OLED display into market can be mainly attributed to remarkable advances in organic semiconductor materials and process technology [3][4][5].However, these OLED displays do still suffer from their short lifetime though the thermal stability of organic materials themselves has been significantly improved when it comes to the test device measurement [4,6,7]. In case of OLED displays made using small molecules, it has been reported that a progressive electrical short (PES) phenomenon is responsible for the degradation of display pixels during long time operation [8]. This report claimed that the PES phenomenon is closely related to the formation of unstable defects in organic layers which eventually leads to catastrophic degradation of whole layers in pixels. In this report the PES phenomenon could be healed by thermal treatment at temperatures below 100 o C in the presence of oxygen. This indicates that the defects become just oxidized in the presence of minimal molecular (translational) movement by thermodynamic effects, which means that the fundamental defects such as voids in either among molecules or between layers cannot be completely recovered.In this work we have attempted to cure these defects by melting organic layers, particularly focusing on a holeinjecting layer (HIL) that is the first layer contacting the anode of passive matrix (PM) OLED display (see the crosssectional device structure in Fig. 1a). The process time of HIL melting was controlled as short as possible in order to *Address correspondence to this author at the Department of Chemical Engineering, Kyungpook National University, Republic of Korea; avoid a large scale deformation of the HIL layer geometry, whilst the melting process temperature chosen was above the intrinsic melting point o...